By Matthew S. Taylor. Last modified 5 January 2010. Certain parts taken from: Howard W. Sams & Co., Inc. ―Wollensak Models T-1500, T -1500, T-1515-4, T-1700, TS-1520.‖ TS-1520.‖ Photofact® Set 564, Folder 15. Indianapolis 6, Indiana: Jan. 1962. ---. ---. ―Wollensak ―Wollensak Model Model TT-1500.‖ Photofact® Set 400, Folder 13. Indianapolis, Indianapolis, Indiana: Indiana: May 1958. 1958.
Introduction This manual is for the Wollensak T1500 tape recorder, which is designed for operation on 120 VAC, 60Hz. Models TS-1520 and T-1700 are similar, differing only in the ability to operate on different supply supply voltages. The TS-1520 model has an autotransformer autotransformer which allows it to operate on 220VAC, 220VAC, 60 Hz as well as 120VAC. 120VAC. The T-1700 model has a vibrator inverter which allows it operate off of 12.6 VDC VDC as well as 120 VAC. The tape record is a complete self-contained self-contained recording and playback unit, with a selfcontained speaker. speaker. The audio output is also made available at the Preamp. Preamp. Jack, allowing it to be fed into an existing home music system, or an external speaker speaker may be connected to the External Speaker Jack.
Versions of the T-1500 I have found there see seems ms to be an ―early‖ and a ―late‖ version of the T-1500 T-1500 chassis, which differ slightly slightly in their electronics. electronics. The ―early‖ chassis was made between approximately 1958 and 1961, and the ―later‖ from 1962 onward. onward . The date of manufacture is stamped on the underside of the electronics chassis. chassis. Although the main main text of this manual manual refers to the later chassis, notes for the 1958 version may be found found in the Appendix on page page 32. In the text, sections sections that differ for the two versions I mark with a ―§‖, ―§‖, so be sure to check the Appendix for them if you have the 1958 chassis!
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Table of Contents
Wollensak Model Model T-1500 Tape Recorder Recorder Service Manual Manual ........................................... ................................................. ...... 1 Introduction ........................................................................................................................ ........................................................................................................................ 1 Versions of the the T-1500 ................................................. .................................................................................................... ....................................................... .... 1 Specifications Specifications................................................ ................................................................................................. ....................................................................... ...................... 6 Frequency Response .................................................................................. ........................................................................................................ ...................... 6 Wow & Flutter................................................... Flutter.................................................................................................... ............................................................... .............. 6 Signal-to-Noise Signal-to-Noise Ratio ............................................... .................................................................................................. ....................................................... .... 6 Tape Speeds ..................................................................................................................... ..................................................................................................................... 6 Tape Required......................... Required............................................................................ ......................................................................................... ...................................... 6 Playing Time .................................................................................................................... .................................................................................................................... 6 Power Requirements Requirements ................................................ ................................................................................................... ....................................................... .... 6 Power Consumption ........................................................................................................ ........................................................................................................ 6 Size ........................................... ............................................................................................ ........................................................................................ .......................................6 Weight .............................................. ............................................................................................... ................................................................................ ............................... 6 Function of Controls, Indicators, and Switches ........................................... ................................................................. ...................... 7 Power Switch ................................................................................................................... ................................................................................................................... 7 Tone Control ...................................................................................... .................................................................................................................... .............................. 7 Volume Control Control................................................. .................................................................................................. ............................................................... .............. 7 Function Keys .................................................................................................................. .................................................................................................................. 7 Stop .............................................. ............................................................................................... ................................................................................ ............................... 7 Record .......................................................................................................................... .......................................................................................................................... 7 Play ......................................................................................................................... ............................................................................................................................... ...... 7 High-Speed Lever ............................................................................................................ ............................................................................................................ 7 Instant Stop & Record Lock Lever .................................................................................. 8 Record Level Indicator .................................................................................................... .................................................................................................... 8 Record Mike/P.A.– Mike/P.A.–Monitor Switch .................................................. ................................................................................ .............................. 8 Speed Selector ........................................................... ............................................................................................................ ....................................................... ...... 8 Index Counter .................................................................................................................. .................................................................................................................. 8 Purpose of Jacks on Rear .............................................................................. .................................................................................................... ...................... 8 Input Jack ........................................................................................................................ ........................................................................................................................ 8 External Speaker Jack ..................................................................................................... ..................................................................................................... 9 Preamp Output Jack .................................................................. ........................................................................................................ ...................................... 9 [2]
Operating Instructions Instructions ........................................................................................................ ........................................................................................................ 9 Preparation ............................................... ................................................................................................ ....................................................................... ...................... 9 Recording with a Microphone ................................................... ......................................................................................... ...................................... 9 Monitoring ............................................ ............................................................................................. ....................................................................... ...................... 9 Recording from an External Source .......................................................................... .............................................................................. .... 10 Tape Erasure ............................................................. .............................................................................................................. ..................................................... .... 10 Playback ..................................................................................................................... ......................................................................................................................... .... 10 Playback with External Amplifier .......................................................... .............................................................................. .................... 10 Splicing & Editing ............................................................. .......................................................................................................... ............................................. 10 Use as a Public Address System ..................................................................................... ..................................................................................... 11 Disassembly Disassembly Instructions Instructions .............................................................................................. .................................................................................................. .... 15 To Remove Mechanism from Case .................................................... ................................................................................ ............................ 15 To Remove Amplifier from Transport Mechanism........................................... Mechanism....................................................... ............ 15 To Remove Amplifier Without Complete Disassembly Disassembly ................................................ ................................................ 15 Replacing Replacing Sound Head ............................................. .............................................................................................. ..................................................... .... 16 Preliminary Preliminary Tests ................................................. .................................................................................................. ............................................................. ............ 16 Function Switch Explanation ....................................................... ............................................................................................. ......................................17 Electrical Electrical Adjustments .................................................................................................... ...................................................................................................... .. 18 Head Azimuth ........................................................... ............................................................................................................ ..................................................... .... 18 High Frequency Equalization Adjustment § ............................................. ................................................................. .................... 19 Hum Balancing Adjustment .............................................................................. .......................................................................................... ............ 19 Bias Current Adjustment § ............................................... ............................................................................................ ............................................. 19 Cleaning ............................................... ................................................................................................. .............................................................................. ............................20 Lubrication ................................................... .................................................................................................... ..................................................................... ....................20 Troubleshooting Troubleshooting Mechanical Mechanical Problems ............................................................................ ............................................................................ 20 No Tape Drive in Play or Record ............................................... ................................................................................... .................................... 20 Take-up Reel Does Not Turn Although Tape Feeds Past the Capstan ......................... ......................... 21 Take-up Reel Stalls in Playback or Record when Reel is Nearly Full ........................... 21 No Fast Forward But Capstan Turns ............................................................................ 21 Fast Forward Stalls with Full Reel ................................................................................ ................................................................................ 21 No Rewind But Capstan Turns .................................................. ...................................................................................... .................................... 21 Tape Overruns or Spills When Functions Are Changed ............................................... ............................................... 21 Speed Irregularities (―Wow‖ & ―Flutter‖) ................................................. ..................................................................... .................... 21 Bottom Motor Shaft Pin Rubs Bottom Ventilating Grill............................................... 22 [3]
Insufficient Insufficient Tape Take-up ............................................................................................. ............................................................................................. 22 Tape Squeal or Squeak ............................................. .............................................................................................. ..................................................... .... 22 Troubleshooting Troubleshooting Electrical Electrical Problems ........................................... ............................................................................... .................................... 22 Weak Playback Playback Volume or No High High Frequencies ............................................. ......................................................... ............ 22 Recorder Dead, Pilot Light Off .................................................................. ...................................................................................... .................... 23 23 No Playback or Record .................................................................................................. .................................................................................................. 23 Plays, But Does Not Record Or Records But Does Not Playback ................................. 23 Weak or Distorted Distorted Record, Playback Playback of Prerecorded Prerecorded Tape Normal Normal ............................. 23 Record Level Indicator Inoperative or Operation Defective ........................................ 24 Hum in Record or Playback...................... Playback....................................................................... ..................................................................... .................... 24 Weak or No Erase, Erase, Records Over Over Previous Recordings Recordings ............................................ ................................................ .... 24 Microphonic Microphonic Noises ..................................................................................................... ....................................................................................................... .. 24 No Sound, Neon Lamp Flashes with Signal .................................................................. .................................................................. 24 Excessive Tape Hiss .................................................. ..................................................................................................... ..................................................... .. 25 Electrical Electrical Components ...................................................................................................... ...................................................................................................... 25 Tubes & Lights § ................................................ ................................................................................................. ............................................................. ............ 25 Capacitors § ............................................... ................................................................................................ ..................................................................... .................... 25 Resistors § ................................................. .................................................................................................. ..................................................................... .................... 26 Inductors & Transformers § ............................................. .......................................................................................... ............................................. 27 Speaker ............................................ ............................................................................................. .............................................................................. ............................. 27 Rectifiers........................................................................................................................ ........................................................................................................................ 27 Fuse............................................................................................................................ ................................................................................................................................ .... 27 Switches § .................................................. ................................................................................................... ..................................................................... .................... 28 Motors .............................................. ............................................................................................... .............................................................................. ............................. 28 Mechanical Mechanical Parts List ...................................................................................................... ........................................................................................................ .. 28 Appendix: Early Version Version Procedures & Components Components .......................................... ...................................................... ............ 32 High Frequency Equalization Adjustment (p. 20) ............................................ ........................................................ ............ 32 Bias Current Adjustment (p. 20) ............................................... ................................................................................... .................................... 32 Electrical Electrical Components ............................................. .............................................................................................. ..................................................... .... 32 Tubes & Lights (p. 26) .......................................... ........................................................................................... ..................................................... .... 32 Capacitors (p. 26).................................................. ..................................................................................................... ..................................................... .. 32 Resistors (p. 27) ......................................................................................................... ......................................................................................................... 32 Inductors & Transformers Transformers (p. 28) ............................................................................. ............................................................................. 32 Switches (p. 29)............................................. .............................................................................................. ............................................................. ............ 33 [4]
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Specifications Frequency Response 3¾ ips: 7½ ips:
40– 40–8,000 Hz ± 3 dB 40– 40–15,000 Hz ± 3 dB
Wow & Flutter Less than 0.3% for both speeds.
Signal-to-Noise Ratio Greater than 48 dB.
Tape Speeds 3¾ and 7½ inches per second.
Tape Required Up to 7-inch 7-inch reel, ―A‖ wound tape (shiny side out).
Playing Time A 7-inch reel of 1-mil 1-mil tape recorded on on both tracks at 3¾ ips will play play for 3 hours; other tape lengths, thicknesses, and speeds are proportional.
Power Requirements Model T-1500: Model T-1520: Model T-1700:
120 VAC, 60Hz. 120 VAC or 220 VAC, 60 Hz. 120 VAC, 60 Hz or 12.6 VDC.
Power Consumption 100 Watts
Size Approximately Approximately 6½ inches by 10¼ inches by 11¾ inches. inches.
Weight T-1500: T-1520: T-1700:
20 pounds 22 pounds 26 pounds
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Function of Controls, Indicators, and Switches Power Switch Rotating the tone control a few degrees clockwise turns the tape recorder on, applying power to both the amplifier amplifier and transport transport motor. Thus the motor is ready to transport the tape immediately whenever the Play or Record keys are pressed or the High Speed Lever actuated. When the tone control control is turned to the the ―Off‖ position, position, a tab on the knob trips the transport mechanism, locking it in the ―Stop‖ position for storage.
Tone Control Turning the knob further varies the tone. The ―Balanced ―Balanced Tone‖ setting emphasizes very high and very low low frequencies, frequencies, the degree of emphasis emphasis varying with the volume volume control setting, thus producing a response which closely matches the normal hearing response of the human ear. The ―Bass‖ setting cuts high frequencies and emphasizes emphasizes low ones. The ―Treble‖ ―Treble‖ setting setting emphasizes emphasizes high frequencies. frequencies. The ―Hi―Hi-Fi‖ position produces a response suitable for use with external amplifiers. amplifiers. The tone control has no effect when recording.
Volume Control This regulates the volume during both recording and playback, as well as adjusting the signal level applied to the Preamp Output jack.
Function Keys Stop
Cancels either playback playback or recording. recording. Brakes are applied to the spindles, spindles, the tape is held away from the head, and the function switch is put into i nto the ―Stop‖ position. Record
Before the record key can be pressed to begin recording, the record lock lever must be pulled. This releases the brakes, brakes, holds the tape against the head using pressure pressure pads, pushes the pressure roller against the capstan (which moves the tape), and turns the function switch to ―Record.‖ Play
Pressing the play key results in the same action as record, except the function switch is put into the ―Play‖ position.
High-Speed Lever Moving this lever to the right causes the tape to advance at a much higher speed than that used during recording recording or playback. When this lever is moved to the left, tape is rewound onto the supply reel. reel. The high-speed lever can be moved when the recorder recorder is
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in any function (Play, Record, or Stop) and the play or record keys will be automatically released. When the lever is returned to neutral, neutral, the recorder is left in the ―Stop‖ mode. mode.
Instant Stop & Record Lock Lever The record lock lever is provided as a safety feature to prevent accidental erasure of prerecorded tapes. tapes. It must be pulled towards the front of the recorder recorder and held there before ―Record‖ ―Record‖ mode can be entered. entered. It also serves as an instant stop lever when the tape is in motion during record or playback. Pulling the instant stop lever disengages disengages the tape drive and instantly stops stops the tape. The recorder returns returns to its previous operation when when this lever is released.
Record Level Indicator During recording, the left or ―Normal‖ half of the indicator flashes to indicate a correct volume setting. The right or ―Distorted‖ half flashes if the volume setting is too high. To present the volume level for recording recording before the record key is pressed, pressed, the tone control should be turned turned to ―Treble.‖ However, after the record record key is pressed, the tone control adjustment adjustment has no effect. When playing prerecorded prerecorded tapes, ignore the flashing of this indicator.
Record Mike/P.A.– Mike/P.A.– Monitor Monitor Switch This is a slide switch mounted on the rear of the tape recorder. When the switch is in the ―Record Mike‖ position, the speaker speaker does not operate in both record and stop modes. This is also true of any speaker which may may be connected to the speaker output jack at the time. time. When this switch switch is in the ―P.A.–Monitor‖ ―P.A.–Monitor‖ position, the speaker is connected so that the recorder can be used as a public-address system, or so that program material may be monitored as it is being recorded. This switch has no effect in playback mode.
Speed Selector The speed selector is mounted near the index counter at the left front of the tape recorder, and sets the speed speed of the tape. The speed selected appears appears on the speed selector dial in inches per second. The recorder does not need to be stopped to change speeds. Rapid forward winding winding can be further accelerated accelerated by selecting 7½ ips.
Index Counter The index counter can be set to zero by turning the knurled knob towards the rear of the tape recorder. If the counter is zeroed when recording recording or playback starts, starts, tape selections may be indexed, thus providing quick and accurate replay or editing.
Purpose of Jacks on Rear Input Jack The input jack can be used to connect a microphone or external audio source to the tape recorder. The proper input circuit is automatically automatically selected selected by means of different [8]
plug lengths for each application. application. A short (1-inch) plug is used with the microphone microphone and a longer (1 316 -inch) plug is used for external audio sources (televisions, radios, &c.).
External Speaker Jack An external external speaker can be connected connected to the tape recorder through through this jack. The impedance of the speaker should be 6-8Ω. 6-8Ω. Accessories such as the TE-401 TE-401 earphone or headphones may also also be used. The internal speaker is disconnected disconnected when a plug is inserted into this jack.
Preamp Output Jack The preamp output jack is provided for connection to an external audio amplifier, bypassing the internal internal output stage stage and speaker. speaker. The output impedance impedance is approximately 33 ĸΩ.
Operating Instructions Preparation 1. 2. 3. 4.
Connect the tape recorder to the proper power source using the cord provided. Make sure the high-speed lever is in the center or neutral position. Turn the recorder on by rotating the tone control a few degrees clockwise. Threading the Tape a. Press the stop key. b. Place a full reel of tape (glossy side out, i.e. ―A‖ wind) on the left spindle. c. Pull a length of tape off the supply reel and lower it into the threading slot. d. Attach the end end of the tape to the empty empty take-up reel. e. Set the index counter to zero.
Recording with a Microphone 1. 2. 3. 4.
5. 6. 7. 8. 9.
Insert the microphone plug into the input jack on the rear of the recorder. Set the slide switch to ―Record Mike.‖ Select the desired tape speed. If you wish to preset the record level, then: a) Turn the tone control to ―Treble.‖ b) Adjust the volume control until the ―Normal‖ ―Normal‖ half of the indicator indicator flashes. c) No flashing should occur on the ―Distorted‖ half. Pull back the Instant-Stop-Record Lock Lever and press the record key. Release the Instant Stop Lever. Recording will start. To stop recording, press the stop key. To rewind the tape, move the high-speed lever to the left. Monitoring
The signal can be monitored during recording if the slide switch on the rear panel is set to ―P.A.–Monitor.‖ However, care must must be taken to keep the microphone away away from the [9]
speaker, otherwise otherwise acoustic feedback feedback may cause squealing. This hazard can be avoided if earphones are used instead instead of the internal speaker. The earphones should be plugged into the external speaker jack. Also, before rewinding rewinding the tape, additional additional material material may be recorded recorded by turning over the full take-up reel and placing it on the supply spindle.
Recording from an External Source 1. Connect the signal source to the input jack using an A196-13 Hi-Fi cable, or similar cable with a long plug. 2. Proceed with steps 2 to 9 for ―Microphone Recording‖ given above. above. Recordings can be made from external sources such as phonographs, radios, televisions, or AM-FM AM-FM tuners. If the external source has has a level control for its output jack being used, it should should be set so that that the tape recorder’s recorder’s volume control control setting will will be somewhere near near its midrange for proper operation operation of the level indicator. Tone controls and loudness controls on the external source should be set to a flat setting.
Tape Erasure Whenever a recording recording is made, any previously-recorded previously-recorded material on the the tape is automatically automaticall y erased before the new material is recorded. Erasing is performed only when the recorder recorder is set to ―Record.‖ ―Record.‖ Half of the tape is erased at a time. To erase without recording recording new sound, turn the the volume control control down completely completely before entering entering ―Record‖ mode.
Playback 1. 2. 3. 4. 5. 6.
Thread the tape as described under Preparation Step 4, a-e. Locate the desired starting point using the High Speed Lever. Set the speed selector to the speed used when the material was recorded. Push down the play key. Adjust volume and and tone as desired. desired. For dual-track recordings, do the following: a) Turn over the tape at the end of the first track. b) Put it on the supply on the supply spindle. c) Rethread the tape and play as before. Playback with External Amplifier
1. Connect the external amplifier to the preamp output jack on the back of the recorder using a shielded cable such as Wollensak A196-13 Hi-Fi cable. 2. Set the recorder’s tone control to ―Hi―Hi -Fi.‖ 3. Adjust the recorder’s recorder’s volume until until the ―Normal‖ ―Normal‖ side of the level indicator flashes. 4. Adjust the amplifier’s amplifier’s volume and tone controls as desired.
Splicing & Editing Tape from a dual-track tape recorder may be edited only if one track has been recorded or if the program on the other other track is not wanted. Undesirable portions portions can be cut out, announcements announcements can can be inserted between between selections, selections, and so on. Unused [10]
sections of tape can be spliced spliced together and reused. Tape should be cut on a diagonal and the ends joined together with splicing splicing tape on the glossy side. Any excess width should be trimmed. Program material can be edited very precisely in the following manner: 1. Press ―Play‖ key and stop the tape with the instant stop lever. 2. Turn the reels by hand to locate the word or sound. 3. Remove the head cover and mark the tape at the right-hand element in the black slot of the sound head. 4. Remove the tape from the threading slot and cut on the mark.
Use as a Public Address System 1. 2. 3. 4. 5.
Press the stop key of the recorder. Set the slide switch to ―P.A.–Monitor.‖ Plug the microphone into the input jack. Plug an external speaker or speakers into the external speaker jack. Keep microphone and speaker(s) separated as far as possible to avoid feedback.
Figure 1: Top View of Transport Mechanism
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Figure 2: Top Plate Mechanism
Figure 3: Transport Mechanism with with Top Mechanism Mechanism Plate Removed
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Figure 4: Exploded View of Transport Mechanism
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Figure 5: Exploded View of Top Mechanism Plate Plate
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Disassembly Instructions To Remove Mechanism from Case 1. Remove top panel. a) Remove five (5) painted screws holding top panel (three screws between reel spindles and one on each forward corner). b) Remove two chrome-plated screws screws on top of perforated grill directly in front of head cover. c) Remove clean-out cover bar by pulling upward. d) Carefully pry up the top panel at the rear enough to just clear the reel spindles. e) Pull back the panel to remove. 2. Remove bottom cover by removing the following: a) Four (4) screws in line with and inside rubber feet b) Two (2) screws on side panels panels a half-inch above rear feet. (For Model T-1700, one screw on left side-panel, the other inside right rear foot.) c) Two (2) screws one-inch to the side of the top cover hinges. d) Lastly the bottom cover. 3. Remove counter belt from counter pulley. 4. Remove high-speed knob by pulling up. 5. Remove the three remaining Philips head screws from each side panel. 6. Remove side panels. 7. For Models TS-1520 and T-1700, remove the additional power plug to remove the left-side casting.
To Remove Amplifier from Transport Mechanism 1. 2. 3. 4.
Unplug motor plug. Unplug head plug. Remove nylon function switch arm from bottom of amplifier by pulling off. Remove four Philips head screws (3 long, 1 short) from bottom of amplifier chassis holding each corner. 5. Lift amplifier chassis away from tape transport mechanism.
To Remove Amplifier Without Complete Disassembly 1. Turn Speed Selector to 7½ ips. 2. Remove bottom cover and right side panel as outlined above in ―To Remove Mechanism from Case‖ steps 2, 5, and 6. 3. Pull the nylon function switch arm out of the chassis bottom. 4. Unplug the head plug, motor plug, and speaker plug. 5. For Models TS-1520 and T-1700, remove the additional power plug. 6. Remove the four Philips head screws holding the chassis corners to the mechanism. 7. Note the position of the plastic insulator between chassis and mechanism. 8. Lift chassis up and to the right to remove. 9. When reassembling, reassembling, make sure sure mechanism mechanism is in the 7½ ips position position and the nylon nylon chassis insulator is in place!
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Replacing Sound Head 1. 2. 3. 4. 5.
Remove head retainer spring (137). Lift head and brass alignment plate from head shield cup. Unplug head cable plug. Pry head from brass alignment plate, noting position of location pins. Place the new head over the pins in the aligning plate in the proper location and press into place. 6. Replace alignment plate into head cup, making sure the two brass pivot studs engage the two holes in the plate. 7. Replace head retainer spring. 8. Align head azimuth azimuth as described described on page 18.
Preliminary Tests Failure to pass any of these tests indicates a fault that should be remedied! 1. Cleaning a) Remove head cover casting (3) and pull out clean-out cover casting (4). b) Clean heads, tape guides, and capstan with isopropyl alcohol. 2. Setup a) Press stop key. b) Place high-speed knob in the middle or neutral position. c) Turn on recorder by rotating tone control. 3. Testing Brakes a) Place reel of tape on rewind (left) spindle. b) Pull out about 12 inches of tape. c) Brakes should be engaged. d) Pull required on reel should not distort the tape, but there should be sufficient drag to prevent spilling of tape. e) Drop tape in threading slot, and attach free end to take-up reel (right). f) Reel should rotate freely counterclockwise and drag when rotated clockwise. 4. Playback Mechanism Test a) Press play key; it should latch down. b) Brakes on both spindles should release. c) Record pressure pad assembly (142) and erase pressure pad assembly (143) should press tape squarely against head. d) Pressure roller (103) should push tape against flywheel-capstan flywheel-capstan assembly (47) causing tape to move smoothly past the head as it passes flyback-capstan flyback-capstan assembly (47). e) The counter should tally each revolution of the supply reel. 5. High-Speed Test a) Move high-speed knob to the right. b) Play key should release. c) Pressure roller and pressure pads should release. d) The tape should move forward at greatly increased velocity. 6. Pressure Pads & Braking a) Return high-speed knob to the middle or neutral position. b) Pressure pads and pressure roller should remain disengaged. [16]
c) Brake pressure on spindles should increase smoothly, bringing tape to a stop without spilling. spilling. 7. Recording System Test a) Make a recording with the microphone. b) Adjust volume control control while speaking so that that normal indicator indicator flashes and and distorted does not. 8. Rewind Test a) Move high-speed knob to the left. b) Record key should release and the tape should rewind quickly. 9. Playback Test a) Playback recording. b) Check volume, tone, and overall quality. c) Pull instant stop arm (104) forward. d) Tape should stop at once. e) When arm is is released, tape should should start instantly instantly without spilling spilling off reels. reels. 10. Erasure Test a) Rewind tape and rerecord over previous recording. b) All trace of previous previous recording recording should be erased on on the portion of tape reused. reused. c) Check for irregularities in playing speed (―wow‖ and ―flutter‖).
Function Switch Explanation The function switch is a ―slide‖ wafer type with three positions (play, stop, and record). It has 10 copper strips mounted mounted on two sliding phenolic wafers that that short various stationary stationary contacts together. The wafers can hold hold 36 stationary stationary contacts in total, but only 31 of these are are used on the T-1500, TS-1520, TS-1520, and T-1700 models. models. Being as both the strips and the contacts are placed at several different ―levels‖ along each wafer, it is difficult to see which contacts are shorted together in each of the three positions. Howard Sams did an atrocious job of illustrating this switch in their schematic, and gave no written clarification of it. In my schematics, I show the function switch as ten SP3T and three SPST switches ganged together. The positions of SP3T switch correspond correspond to the play, stop, and record modes respectively. respectively. The SPST switches are engaged engaged in either play or record as specified. specified. My pin numbering is the same as Sam’s: with the knob-side knob-side of the chassis to the left, the numbering proceeds left to right, bottom to top. Though electrically and functionally identical to identical to the actual switch, switch, my depiction makes it much, much much easier to follow. By following my clarified schematic, the action of the function switch is as follows:
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SW S1
S2 S3 S4
S5 S6
S9
S10 S1113
S15, 16
Playback Input jack shorted.
Stop Record Input jack connected Input jack connected to to preamplifier thru preamplifier. C1. Tone control active. Tone control disabled. Equalization selected. Equalization disabled. Erase head and biasErase head and bias-oscillator coil not shorted. oscillator coil shorted (erase disabled). R ead/write ead/write head ――-― grounded. R/W head ――-― connected thru K 1 to signal to be recorded. R/W head ―+‖ R/W head ―+‖ grounded. connected to preamplifier. V 2B V 2B 2B amplifier on. 2B amplifier off; functions as diode, mixing amplified audio from V2A with oscillator signal. Amplified audio at at Preamplifier output jack shorted. output jack. V 4 configured as pentode amplifier. V 4 configured as triode oscillator. Speaker connected to Speaker connected to Speaker connected to output output. output only if ― if ―P.A.‖ P.A.‖ thru R 45 if ―Monitor‖ 45 only if ―Monitor‖ selected. selected.
Electrical Adjustments Head Azimuth It is important the head be lined up so that the record-playback (read/write) head gap is at a 90° angle with respect to the direction of tape travel. travel. If the head is misaligned, there will be some loss of the higher frequencies and a lower l ower overall output. An alignment alignment tape, which used to be be available from Ampex® Ampex® or the larger larger radio supply houses*, should be used to align align the head. The tape should have a full-track recording at a frequency higher higher than six kilohertz. kilohertz. While the alignment alignment tape is being played, adjust alignment alignment screw (140) for maximum output. output. Cement screw screw with Locktite®. If an alignment tape is not available, play a previously-recorded previously-recorded tape and adjust alignment screw (140) for maximum treble response. Azimuth is the only head adjustment needed on Models T-1500, TS-1520, and T-1700.
*
I do not know where such an alignment tape could be found now — now —MST.
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High Frequency Equalization Adjustment § An adjustment adjustment is provided in the cathode cathode circuit of V 2A 2A (12AT7) to compensate for high frequency losses which accompany long-term long-t erm head wear. This equalization has more effect upon the playback playback than it has upon the recording recording process; therefore, the adjustment is made for best results during playback. The equalization adjustment has been properly made at the factory and should not require readjustment readjustme nt for at least 500 hours of use. Before any adjustment is made, the heads should be carefully carefully cleaned with isopropyl isopropyl alcohol. Make the adjustment adjustment in the following manner: 1. Record signals of equal amplitude at 10 kHz and 15 kHz, well below (-15 dB) normal level. 2. Set the tone control for ―Hi―Hi-Fi.‖ 3. Measure the two signals at the Pre-amp output jack during playback using an oscilloscope. 4. With a plastic a plastic adjustment tool, adjust the core of the peaking coil (L3) so that the output at 15 kHz is the same as at 10 kHz, using the 10 kHz signal as a reference. The threaded shaft of the core is accessible from the tube side of the chassis, near hum control R 29 29 between transformers T 1 and T3.
Hum Balancing Adjustment Two access holes are provided in the bottom cover (near manufacturer’s label) for adjustment of hum controls R 29 29 and R 31 31. The access hole nearest the manufacturer’s label provides for the adjustment of R 29 29, and the other for R 31 31. Adjust them using a small bladed screwdriver. Adjust hum controls controls R 29 29 and R 31 31 as follows: 1. Turn tape recorder on and allow tubes to warm up. 2. Press play key. Do not use a tape. 3. Turn volume control to ―0‖ position (minimum). 4. Adjust R 29 29 for minimum hum. 5. Turn volume control to the ―10‖ position (maximum) and adjust R 31 31 for minimum hum. If R 31 31 adjusts for minimum hum at one end of its rotation, leave volume control at maximum and readjust R 29 29 for minimum hum.
Bias Current Adjustment § 1. Remove bottom cover of tape recorder (see ―To Remove Mechanism from Case‖ on page 15). 15). 2. Unplug 4-prong head plug M11. 3. Remove a half-inch of insulation from a length of hook-up wire. 4. Wrap several several turns of the bare bare wire around pin #2 of of the head plug. 5. Reinsert plug into socket, being careful not to short the wire to the chassis or another pin on the plug. 6. Connect a VTVM or DMM† set to read AC RMS volts between the wire (pin #2) and chassis ground. 7. Operate the recorder in ―Record‖ mode. †
Capable of accurately measuring a 75 kHz signal.
[19]
8. With a plastic a plastic (not metal) flat-bladed adjustment tool, adjust bias/erase oscillator coil T 4 for a voltage of 50 VAC.
Cleaning The majority of defects, other than wear or breakage, can be traced to dirty surfaces. The play-record and erase heads, capstan, and pressure roller are subject to an accumulation to tape coating residue, which is worn off the tape as it passes these parts. This accumulation should be periodically removed since it will cause faint recording and poor playback. playback. Wipe off the above surfaces carefully carefully using a clean cloth dampened dampened slightly with isopropyl alcohol.
Lubrication All moving parts parts in this recorder recorder were permanently permanently lubricated lubricated at time of manufacture. Under normal normal use, further further lubrication lubrication should not be required. required. In heavyduty service, the following parts should be lubricated once a year with a drop of light lubricating oil: The top and bottom motor bearings. The top and bottom flywheel (47) bearings. Pressure roller (103) bearing. All idler and drive drive wheel bearings. bearings. The reel spindle bearings. The basic rule is— is—do not over not over lubricate! Oil must be must be kept off all rubber idlers, belts, the periphery of the flywheel, and any parts that might transfer oil to them. Always wipe excess lubricant from parts that have been lubricated.
Troubleshooting Mechanical Problems No Tape Drive in Play or Record Possible Causes Tape wound around capstan. Pressure roller tension spring (89) broken or disconnected so that pressure roller (103) is not held against capstan. Instant-stop brake spring (91) broken or disconnected. disconnected. Brakes will not release release and the the pull of the capstan may be sufficient to break the tape. Idler drive spring (122) broken or disconnected. Left high-speed idler assembly (120) is not held against motor pulley (55) and flywheel (47). Slow speed idler spring (60) broken or disconnected disconnected and the slow speed idler assembly is not held against motor pulley (55) and flywheel (47). Motor pulley (55) loose on its shaft. [20]
Solution Free stuck tape. Connect or replace the spring. Connect or replace the spring.
Connect or replace the spring. Connect or replace the spring.
Tighten motor pulley set screw.
Grease or oil on high (120) or low speed (58) idler tires. Sticking idler slide (59 or 119)
Wipe lubricant lubricant off tires.
Take-up Reel Does Not Turn Although A lthough Tape Feeds Past the Capstan Take-up belt (45) broken or off pulley (43).
Replace belt or place it back on pulley.
Take-up Reel Stalls in Playback or Record when Reel is Nearly Full Grease or oil on take-up belt (45) or on take-up clutch felt (41).
Clean with alcohol. Replace felt if necessary.
No Fast Forward But Capstan Turns High-speed idler spring (115) broken or disconnected. disconnected. Idler assembly assembly (120) not held against flywheel or spindle cup (13).
Connect or replace spring.
Fast Forward Stalls with Full Reel Grease or oil on idler assembly tire.
Wipe lubricant off tire.
No Rewind But Capstan Turns Rewind spring (32) broken or disconnected. Rewind spindle and tire assembly not held against motor pulley (55)
Connect or replace spring.
Tape Overruns or Spills When Functions Are Changed Brake arm spring (17) broken or disconnected. Brake roller leaf spring (21) broken or disconnected.
Connect or replace spring. Connect or replace spring.
Speed Irregularities (“Wow” & “Flutter”) In general, anything that causes a drag or slipping action other than that occurring during normal operation can cause wow or flutter. Check for binding in the following: Flywheel Bearings: Bearings: Check by moving right and left idler wheels wheels (120) away from the flywheel and rotate rotate the capstan by hand. A slight drag is normally obtained obtained from take-up belt (45). All Idler and and Drive Wheel Bearings Bearings Right and Left Reel Spindles: The brakes should be disengaged or held away before the spindles spindles are turned. Motor bearings. Check by turning shaft by hand.
Check to see that: [21]
Supply reel is free to rotate and is not scraping against against the top plate. Brakes are completely released. Pressure roller roller (103) is making good contact with capstan. capstan. Pressure roller tension spring (89) should not be too weak or too strong. Capstan and pressure roller are clean.
Check for irregularities in the following: Idler wheel surfaces Pressure roller (103) surface Take-up Tension: Tension: The take-up clutch is designed to slip during during normal operation to compensate compensate for the different rate of rotation of a full and an empty reel. reel. Check by holding the right-hand right-hand spindle while while the recorder recorder is in Play mode. The clutch action should be smooth smooth and non-pulsating. If the surface of the take-up clutch (41) is gummy or if the felt is worn, it should be replaced.
Bottom Motor Shaft Pin Rubs Bottom Ventilating Grill Fix by placing washers under motor supports on side rubbing to more-nearly center the motor in grill opening when recorder is in normal position.
Insufficient Tape Take-up Clutch felt (41) may be worn. Replace felt if needed. Take-up action may be increased by adding another washer (46) under take-up pulley assembly.
Tape Squeal or Squeak Tape squeal or squeak is heard as a high-pitched warbling sound that accompanies recording or playback. playback. It can be noticed in quiet surroundings surroundings when listening close close to the sound head with the volume turned down. down. Squeal or squeak can be minimized minimized as follows: Clean head, pressure pads, and tape guides with alcohol. Use a good brand of tape. Inferior tape with insufficient insufficient lubrication may may be helped by treating with silicon lubricant. Replace pressure pressure pad felts. Place thin Teflon® film tape tape over pads if needed. Slightly decrease decrease the tension of pressure pad springs (144 & 145).
Troubleshooting Electrical Problems Weak Playback Volume or No High Frequencies 1. 2. 3. 4.
Check for faulty silicon diodes (D 1 & D2) in voltage doubler power supply. Check for open fuse resistors R 22 22 and R 23 23. Check for low plate voltage to 12AB5 power amplifier tubes. Check for dirty head. [22]
5. 6. 7. 8.
Check pressure pads for weak or improper contact. Wrong type or tape tape or wind. Dull side of tape should should be wound ―in‖ ―in‖ (―A‖ wind). Check head azimuth adjustment. Check head for wear. If head is worn, make compensating adjustment (see ―High Frequency Equalization Adjustment‖ on page 19) or replace if head wear is too great. 9. Check adjustment and condition of L3. 10. If high-frequency response is lacking only at 3¾ ips, check operation of equalization switch S8.
Recorder Dead, Pilot Light Off 1. Check fuse F1. If blown, check for B+ shorts, and make sure power source matches power requirement listed on nameplate. 2. Check power cord and power switch.
No Playback or Record 1. Check tubes and voltages as indicated on schematic diagram. Trouble can be localized by monitoring monitoring output at preamp jack: if signal is present here, here, trouble must be in some succeeding succeeding stage; if no signal is present, trouble may be in preceding stages or in power supply. 2. Check play-record head.
Plays, But Does Not Record Or Records But Does Not Playback 1. Amplifier Function Function Switch Switch Nylon Arm out of Adjustment a. See if switch arm moves the function switch all of the way back when play key is pressed or all the way forward when the record key is pressed. b. The switch arm requires adjustment if pushing the switch arm by hand moves the function switch slide slightly more to the rear or front when the play or record keys respectively are pressed. c. To adjust, turn the hexagon nylon cam so that its pin moves the function slide switch as far as possible, both backward and forward when the play and record keys are pressed. d. To check if adjustment is correct, press the stop key; sight straight down the rear edge of the function switch ⅞-in ⅞-in access hole into the amplifier. The rear edge should appear to bisect the small eyelet on the function switch slide. 2. Check for drag or binding on the function function switch slide. Switch should not require more than 20 ounces (570 grams) to move back and forth. 3. Check recording source; microphone may be dead, or other source may be faulty. 4. Oscillator tube V 4 may be defective; defective; if so, listener may may perceive distortion distortion in playback. 5. Check oscillator coil T 4.
Weak or Distorted Record, Playback of Prerecorded Tape Normal N ormal 1. Check oscillator tube V 4. 2. Check input jack for proper contact. [23]
3. Check microphone microphone or other input source for quality of signal. 4. Check plugs; microphone plug should be a two-circuit two-circuit plug with shielded wire connected to tip and shield shield connected to body. Shaft of plug should be approximately approximately 1-in long. High level sources req require uire a two-circuit plug 3 approximately 1 16 inches long. Failure to push plugs all of the way into jack may may cause distortion. 5. Check record level level indicator lamp. A defective lamp may result in a recording recording level which is too high or too low.
Record Level Indicator Inoperative or Operation Defective 1. Check for out-of-tolerance out-of-tolerance resistors. 2. Check for defective NE-45 bulb. 3. Lamp may glow continuously if there is excessive hum or if the amplifier is oscillating. 4. Distorted indicator should begin to glow when 2V @ 1 kHz appears at preamp output jack if circuit is working properly.
Hum in Record or Playback 1. Check electrolytic capacitors. 2. Check all stages for heater-to-cathode leakage in tubes. 3. Check hum controls for proper adjustment (see ―Hum Balancing Adjustments‖ on page 19). 19). 4. Hum on a recorded microphone signal may be due to a poorly-grounded shield on the cable.
Weak or No Erase, Records Over Previous Recordings 1. 2. 3. 4.
Check for dirt on erase head. Check pressure pads. Check oscillator coil T 4 and oscillator tube V 4. Check erase head continuity.
Microphonic Noises Microphonic Microphonic noises usually develop in the first stages of an amplifier in which the sensitivity is greatest, greatest, but can develop in other stages. Start with the first stage (7025) and try different tubes, selecting the one that is least microphonic. Dress C12 to clear edges of function function switch shield. shield. Dress V 1A 1A grid wire (pin #2) to clear C2. Dress C11 to clear input jack shield.
No Sound, Neon Lamp Flashes with Signal 1. Check speaker and speaker contact switch. 2. Check function switch clips for contact. 3. Check connecting cables, jacks, and plugs in output circuit. Make sure speaker plug is pushed all the way down. 4. Check transformer T2 for open secondary.
[24]
Excessive Tape Hiss 1. 2. 3. 4. 5. 6.
Check for sufficient recording level by comparing to a prerecorded tape. Tape may be worn, try a new tape of good quality. Check V 4 and associated voltages. Check bias-erase oscillator coil T 4 and associated components. Check bias current adjustment (given on page 19). 19). Check the automatic demagnetization circuit which operates by shorting C 12 (220 nF) across the play-record play-record coil at the termination termination of the Record function. This capacitor resonates resonates with the record head to provide a decaying demagnetization demagnetization transient. 7. Head may be microphonic. microphonic. If so, replace head. head.
Electrical Components Tubes & Lights § Part # Lmp1 V1 V2 V3 V4 V5
Use Panel Lamp Preamplifier AF Amplifier Power Amplifier Bias Oscillator, Oscillator, Power Amplifier Record Level Indicator
Type 1847 7025 12AT7 12AB5 12AB5 NE-45
Description Incandescent Low-noise twin triode High-µ twin triode triode Beam-power Pentode Beam-power Pentode Neon Lamp
Capacitors § Part #
Capacitance
C1, C12 C2, C34 C3, C29 C4 C5, C6, C28 C7 C8 C9 C10 C11 C13 C14 C15 C16, C17 C18, C19 C20, C21, C23, C26
220 nF 100 nF 5 nF 22 nF 50 nF 47 nF 1 nF 10 nF 1.5 nF 100 nF 680 pF 680 pF 220 pF 50 nF 47 µF 22 µF
Voltage Rating 100V 400V 50V 50V 50V 400V 50V 50V 50V 100V 50V 50V 50V 400V 200V 350V [25]
Type Polyester Film Ceramic Ceramic Ceramic Film or Ceramic Part of Thick-film Printed Circuit K 1 Polyester Ceramic Part of Thick-film Printed Circuit K 2 Film Electrolytic Electrolytic
C22 C24, C27 C30 C31 C32 C33 C35 C36 C37 C38, C41 C39 C40
47 nF 33 µF 22 nF 3.3 nF 100 pF 470 pF 47 µF 100 pF N150 100 µF 2 nF ±10% 220 pF 2 nF
250VAC 350V 250V 100V 500V 1 kV 6.3V 50V 35V 50V 50V 50V
X-Y Metalized Film Electrolytic Part of Thick-film Printed Circuit K 3 Electrolytic Ceramic Electrolytic Ceramic or Polyester Ceramic Ceramic
Resistors § All resistors resistors ½W or less carbon-film carbon-film types types unless otherwise otherwise noted. Part # Value Notes R1 22 MΩ Replace with Digi-Key Part #PPCHHJ22MCT-ND #PPCHHJ22MCT-ND if bad. R2, R12 10 MΩ R3, R10, 10 kΩ R11 R4 10 Ω R5 270 kΩ R6, R13 220 kΩ 2W metal-film R7, R39 33 kΩ R8 200 kΩ with tap @ Carbon potentiometer used as tone control, has 20 kΩ switch on shaft. R9 200 kΩ with tap @ Carbon potentiometer used as volume control. 100 kΩ R14, R17 200 kΩ R15 2.2 MΩ Part of Thick-film Printed Circuit K 1 R16 27 kΩ R18, R36 1 MΩ R19 22 kΩ R20 62 kΩ Part of Thick-film Printed Circuit K 2 R21 220 kΩ R22 22 Ω 5W fusible wire-wound R23, R24 100 Ω 5W wire-wound R25 1.5 kΩ ½W R26 1.5 kΩ R27 22 kΩ R28 47 kΩ R29, R31 250 Ω 2W wirewound potentiometers used as hum [26]
adjust. R30 R32 R33 R34, R35 R36 R37 R38 R40 R41 R42 R43 R44 R45
2.2 Ω 1.8 kΩ ±5% 100 kΩ 270 kΩ 1 MΩ 300 Ω ±5% 680 kΩ 91 kΩ ±5% 180 kΩ ±5% 360 kΩ ±5% 300 Ω ±5% 10 kΩ 82 Ω
Part of Thick-film Printed Circuit K 3
4W wire-wound 3W wire-wound
Inductors & Transformers § (The current given for the power transformer transformer is the measured measured nominal current; current; a replacement must be rated for at least twice this!) Part # Name Details L1 Recording & Playback Head L2 Erase Head L3 Equalization Coil T1 Power Transformer Primary: 120V @ 0.2A Sec. 1: 180V @ 10 mADC) Sec. 2: 12.6V @0.4A Sec. 3: 6.3V @ 1A T2 Output Transformer Transformer Primary Impedance: 1.5 kΩ CT Sec. 1 Impedance: 125Ω CT Sec. 2 Impedance: Impedance: 8Ω T3 Driver Transformer Transformer Turns Ratio: 6/5 to each secondary T4 Bias Oscillator Coil
Speaker SPK1
5¼-in. 5¼-in. PM 8Ω Loudspeaker
Rectifiers Part # Original Wollensak # D1, D2 A123-5 D3 A123-4
Replacements 1N1763 or 1N4004 1N4004 1N4007
Fuse F1
1¼-ampere 125VAC time-delay fuse [27]
Switches § Part # S1-S6, S9-S13, S15, S16 S7 S8 S14
Description Part of Function Slide Switch Power switch on tone control, SPST Equalization Switch, SPDT Mic-Rec/Monitor-P.A. Mic-Rec/Monitor-P.A. Switch; SPDT
Motors M1
Drive Motor
Single-phase hysteresis induction motor
Mechanical Parts List Reference # Quantity Q uantity 1 5 2 2 3 1 4 1 5 1 6 3 7 1 8 1 9 2 10 2 11 1 12 2 13 1 14 1 15 2 16 2 17 1 18 1 19 1 20 2 21 2 22 1 23 2 24 1 25 3 26 1 27 1 28 1 29 1 30 1 31 1
Description #6-32 × 7/32 in. screws #4-48 × ¼ in. screws Head Cover Casting Clean Out Cover Casting Cover Plate #6-32 × 7/32 in. screws Odometer Bezel Casting Front Screen Group Spindle Cup Flat Washer Rewind Spindle & Tire Assembly Spindle Cup Tire Spindle Cup & High-speed Drum Assembly Counter Drive Belt Phenol Washer ―E‖ Ring, ¼ in. Shaft Brake Arm Spring Left Brake Arm Assembly Right Brake Arm Assembly Brake Arm Roller Brake Roller Leaf Spring Spacer Brake Release Link Grip Ring ―E‖ Ring, ¼ in. Shaft Rewind Spindle & Arm Assembly Rear Slide Cam Assembly Right Scissors Detent Spring Left Scissors Detent Spring [28]
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75
1 1 1 2 1 1 1 1 1 1 3 1 3 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 2 1 1 2 2 2 3 3 2 2 1 1 1
Rewind Spring Counter Worm Shaft & Bracket Assembly Counter Assembly #8-32 × 5/32 in. Pan Head Screws Counter Worm Gear Washer Grip Ring, 3/16 in. Shaft Washer Clutch Plate & Felt Assembly Take-up Clutch Felt Clutch Plate Spring Take-up Pulley Assembly ―E‖ Ring, ⅛ in. Shaft Take-up Belt (WALSCO Part #1410-14) Flat Steel Washer Flywheel, Capstan, and Hub Assembly Steel Ball ―E‖ Ring, 3/16 in. Shaft Key Return Lever Key Return Lever Shaft 1/16 in. × ⅜in. Roll Pin Pin Take-up Actuating Lever Take-up Lever Spring Motor Pulley Set Screw Felt Washer Slow Idler Assembly Slow Idler Slide Assembly Slow Speed Idler Spring Washer ―E‖ Ring, 3/16 in. Shaft Speed Nut 3¾ ips Speed Change Arm ―E‖ Ring, 3/16 in. Shaft Lock Nut Large Washer Spacer Sleeve Thimble Grommets Small Steel Washer Large Steel Washer Hex-head Screw Steel Washer Steel Washer [29]
76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119
1 2 1 1 1 1 1 1 1 1 3 1 1 1 1 1 1 1 2 2 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 2 1 2 2 2 2
Motor and Plug Assembly, Assembly, 115VAC, 60 Hz ―E‖ Ring, ¼ in. Shaft Flat Steel Washer Motor Fan Washer Slow Speed Switch Cam ―E‖ Ring, 3/16 in. Shaft Cam Actuating Stud Lever Assembly ―E‖ Ring Bottom Mechanism Plate Assembly #8-32 × ¼ Pan Head Screws Top Mechanism Plate Assembly ―E‖ Ring, 3/16 in. Shaft Pressure Roller Tension Spring Function Switching Arm Assembly Instant Stop Brake Spring ―E‖ Ring, 3/16 in. Shaft Function Roller Slide Roller ―E‖ Ring, 3/16 in. Shaft Instant Stop Brake Arm ―E‖ Ring, 3/16 in. Shaft ―E‖ Ring, 3/32 in. Shaft Slide Roller Instant Stop Guide Arm ―E‖ Ring, 5/32 in. Shaft Fiber Washer Pressure Roller Assembly (WALSCO Part #1427-01) Instant Stop Arm and Stud Assembly Pressure Roller Arm Assembly Arm High-speed Forward Lever Washer Spring Play Key Assembly Record Key Assembly Stop Key Assembly Key Shaft ―E‖ Ring, 3/16 in. Shaft High-speed Idler Spring Speed Nut ―E‖ Ring, 3/16 in. Shaft Washer Idle Slide Assembly [30]
120 2 Idler Assembly Assembly (WALSCO Part #41-040) 121 1 Spring Retainer 122 1 Idler Drive Spring 123 1 7 ½ ips Speed Change Arm 124 1 ―E‖ Ring, 3/16 in. Shaft 125 1 ―E‖ Ring, 3/16 in. Shaft 126 1 Two Speed Knob Assembly 127 1 Detent Spring 128 1 Steel Ball 129 1 Cotter Pin 130 1 1/16 in. × ⅜ in. Roll Pin 131 1 Two Speed Arm Shaft 132 1 High-speed Slide & Key Return Lever Assembly 133 2 ―E‖ Ring, 3/16 in. Shaft 134 1 Key Return Lever Spring 135 1 Brake Release Spring Monaural Half-Track Head Assembly 136 2 #3-48 #3-48 × ⅛ in. Screw 137 1 Head Hold-down Spring 138 1 Head Insulator 139 1 Play-Record-Erase Play-Record-Erase Head 140 1 #4-48 Set Screw (for Head Adjustment) 141 2 ―E‖ Ring 142 1 Record Pressure Pad Assembly 143 1 Erase Pressure Pad Assembly 2 Felt Pressure Pads 144 1 Record Pad Spring 145 1 Erase Pad Spring
[31]
Appendix: Early Version Procedures & Components High Frequency Equalization Adjustment (p. 19) In step 4, you were instructed to adjust the peaking coil for 6 dB (twice the voltage) more output at 10 kHz than at 15 kHz.
Bias Current Adjustment (p. 19) Bias is measured by placing a 100 Ω resistor in series with the record element and measuring the voltage across this resistor with a meter capable of accurately reading 0.15V @ 70 kHz.
Electrical Components Tubes & Lights (p. 25)
Early versions used a #47 panel lamp for Lmp 1 and a 12AX7 for V 1. Capacitors (p. 25)
Part #
Capacitance
C1 C4 C11 C12 C16,C17 C37 C39
Not used. 15 nF 25 nF 100 nF Not used. 22 µF Not used
Voltage Rating
Type
50V 50V 200V
Ceramic Ceramic Polyester
35V
Electrolytic Electrolyti c
Resistors (p. 26)
Part # R1 R30,R48 R41 R42 R44 R46 R47
Value Notes Not used 4.7 Ω 2W wire-wound 82 kΩ 180 kΩ 4.7 kΩ 1.8 kΩ 470 kΩ
Inductors & Transformers (p. 27)
Part # Name T1 Power Transformer Transformer
Details Primary: 120V @ 0.4A Sec. 1: 200V @ 7 mA) Sec. 2: 12.6V @0.4A Sec. 3: 6.3V @ ¾A [32]
T2
T3 T4
Output Transformer Transformer Primary Impedance: 8.8 kΩ CT Sec. 1 Impedance: 130Ω CT Sec. 2 Impedance: 8Ω Driver Transformer Primary Impedance: 25 kΩ Sec. 1 & 2 Impedance: Impedance: 13 kΩ Bias Oscillator Oscillator Coil Different winding inductance. Switches (p. 28)
Part # S1-S6, S9-S11, S13-S15 S7 S8 S12
Description Part of Function Slide Switch Power switch on tone control, SPST Equalization Switch, SPDT Mic-Rec/Monitor-P.A. Mic-Rec/Monitor-P.A. Switch; SPDT
[33]
