Mark Simpson DC-37R Schematic

Mark Simpson DC-37R

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Product Information:
Model:DC-37R
Manufacturer:Mark Simpson (MASCO)

Schematics Content

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SPECIFICATIONS
POWER CONSUMPTION: 80 watts at 117 volts, 60 cps (Models D - 37, DC - 37, LD - 37) 95 watts at 117 volts, 60 cps (Models D - 37R, DC - 37R, LD - 37R)
POWER OUTPUT: 5 WATTS (to internal or external speaker)
HUM LEVEL: 50 db below full output
FREQUENCY RESPONSE: 80-8500 cps + 3 db at 7.50" / sec. 80-5000 cps + 3 db at 3.75" / sec.
SIGNAL - TO - NOISE RATIO: 45 db at 7.501 / sec. 40 db at 3.75" / sec.
ERASE AND BIAS FREQUENCY: 60 Kc
INPUTS:
(1) Microphone-l megohm impedance,. 003 volts sensitivity
(1) Radio - Phono - 0.5 megohm impedance, 0.4 v. sensitivity
(1) External Speaker, 8-16 ohm voice coil, 5 watts
(1) External Amplifier, 500 ohms, 1.7 volts to line or amplifier (any 500 ohm or high impedance radio-phono input may be used)
MONITORING: The EXTERNAL SPEAKER jack takes a phono-type plug and may be used with any headphones for HEADPHONE MONITORING simultaneously with recording. The INTERNAL SPEAKER may also be used for monitoring.
MONITOR SWITCH: On tone control AMPLIFIER CONTROLS: (1) Volume; (1) Tone
SPEAKER: 6" PM. 3.2 ohm voice coil
PLAYBACK EQUALIZATION Separate for each speed
REWIND SPEED: 1200 feet in 3 minutes (approx.)
RECORDING VOLUME LEVEL INDICATOR: Neon bulb also acts as Pilot Light in "PLAYBACK" TAPE TIME (with 1200' reel): 7.50" / sec. i hr. dual track; 1/2 hr, single track 3.75" / sec, 2 hrs. dual track; 1 hr. single track
TAPE: Any "A" wound tape (dull or twiced side facing in to ward hub of reel) may be used.
AMPLIFIER TUBES:
(1) 12AX7 equalized tape playback pre-amplifier
(1) 6SL7GT dual purpose microphone voltage amplifier and intermediate amplifier.
(1) 6SN7GT dual purpose: recording head driver in "RECORD" output amplifier tube driver in "PLAYBACK"; monitor amplifier in "RECORD"

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(1) 6V6GT 60 Kc. Bias and erase oscillator in " Record power output amplifier in "Playback".
(1) 6X5GT full wave rectifier AM RADIO TUNER: (Models D - 37R, LD - 37R, DC - 37R only); TUBES:
(1) 6BA6 RF amplifier
(1) 6BE6 Oscillator-converter
(1) 6SF7 IF amplifier and detector
(1) Selenium Rectifier Radio ON - OFF Switch on radio tuner operates a seperate power supply for the tuner.

CALL OUT DIAGRAM LEGEND
1. SUPPLY REEL Reels up to 7" in diameter may be used.
2. SUPPLY REEL SPINDLE Threaded (6-32) to permit bolting down of reels.
3. TAPE SLOT Can be used for attaching recording counter.
4. RECORD AND ERASE HEAD Shure Type TR5H. Head mounts on head alignment pins and may be replaced without any special alignment tools. Head is kept firm by means of a felt pressure pad.
5. TAKE - UP REEL 7 supplied with recorder.
6. TAKE - UP REEL SPINDLE Threaded (6-32). Braking pressure is applied to this spindle shaft during "Rewind" to ensure even winding of tape and to prevent slippage.
7. ELAPSED TIME INDICATOR SCALES
8. CAPSTAN TURRET Feeds tape at constant speed.
9. CONTROL LEVER No. 1-82. position control:
Position 1: Off - Stop tape Rewind Position 2: Record Playback
10. RECORD PUSHBUTTON Used for recording at either speed. This button must also be depressed to ERASE
11. MAIN POWER SWITCH Turns on amplifier and motor. If control levers are at OFF motor will idle with capstan disengaged.
12. TONE CONTROL AND MONITOR SWITCH Continuous Treble attenuation type tone control, The control is not effective when recording, CORRECT tonal values being determined by the equalizing circuits. The MONITOR SWITCH, operated by the tone control, allows the user to listen while recording.
13. SPEAKER
14. VOLUME CONTROL Used for adjusting the recording volume level and also for controlling the volume in " Playback *
15. MICROPHONE INPUT Takes standard phone-type plug.
16. 3.75 SPEED CHANGE PUSHBUTTON Used only when recording or playing back at 3.75" / sec.
17. CONTROL LEVER No. 2- a 3- position control:
Position 1 Rewind
Position 2: Off - Stop Tape
Position 3: Record Playback
18. VOLUME LEVEL INDICATOR AND PILOT LIGHT Neon bulb acts indicator of correct recording volume in "Record" and as pilot light at all other times.
19. TUNING CONTROL For built-in AM radio (models with radio only).
20. RADIO ON - OFF SWITHH Main power switch must be ON to permit radio to be operated (models with radio only).
21. RADIO DIAL
22. MICROPHONE STORAGE COMPARTMENT (on models without radio only)
23. BUMPER FEET
24. REMOVABLE BACK Perforated for ventilation and provided with safety interlock to automatically disconnect power when back is removed.
25. AC POWER CORD For operation on 117 volts, 60 cycles AC only.

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26. EXTERNAL SPEAKER AND MONITOR JACK Delivers full audio power to external 8-16 ohms speaker or headphones.
27. EXTERNAL AMPLIFIER OUTPUT
28. RADIO AND PHONOGRAPH INPUT Any radio, tuner or phonograph can be adjusted for use with this input.

TAPE RECORDER, RADIO TUNER, VOLTAGE AND RESISTANCE CHARTS

All voltages to ground, measured with 20,000 ohm / volt meter. All resistances measured to ground. 20,000 ohm/volt meter.

INSTALLATION
This recorder is designed to operate from 105-125 volts 60 cycles AC. Operation on any other voltage or frequency may result in serious damage and / or improper operation and will void the guarantee. If in doubt consult your MASCO dealer or power company.
1. Insert the AC power plug into any 105-125 volt, 60 cycle AC socket.
2. Remove full reel of tape, empty take-up reel and microphone from storage.

OPERATION
Before reading the operating instructions, it is suggested that you familiarize yourself with the various controls and features of your recorder as described in the preceding pages.

TO RECORD FROM MICROPHONE
1. Make certain that CONTROL LEVERS No. 1 and 2 are at OFF.
2. Place MAIN POWER SWITCH TO ON
3. Place full reel of tape on the SUPPLY REEL SPINDLE, so that the glossy side of the tape faces you and the reel will unwind counter-clockwise. Make certain that one of the slots in the hub of the reel engages the fin or key of the reel spindle.
4. Place the empty take-up reel on the TAKE - UP REEL SPINDLE, making sure that the reel slot engages the f'in at the base of the spindle.
5. Unwind about 2 feet of tape from the Supply Reel. Drop the tape into the TAPE SLOT and run it in FRONT of the tape guide pin on the right of the RECORD HEAD housing.
6. Insert free end of tape into slot on take-up reel and rotate the reel counter-clockwise (to the left) for a few turns until the tape is engaged. BE SURE THAT THE GLOSSY SIDE OF THE TAPE FACES YOU. Rotate reel to take up slack.
7. By this time the neon-bulb PILOT LIGHT should be glowing steadily to indicate that the equipment is warmed up and ready to operate. Plug microphone into MICROPHONE INPUT.
8. Depress the RECORD PUSHBUTTON. While keeping the button depressed, rotate CONTROL LEVER No. 1 to "RECORD" position.
9. The PILOT LIGHT goes out as a result of the above operation and becomes the RECORDING VOLUME LEVEL INDICATOR. Hold the microphone firmly in the hand about 6 to 12 inches away from the mouth. While speaking into the

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microphone in a normal tone of voice, rotate the VOLUME CONTROL clock wise until the neon bulb VOLUME LEVEL INDICATOR flickers occasionally. The VOLUME CONTROL should not be advanced to the point where the neon bulb glows continuously, to avoid distortion. IT IS RECOMMENDED THAT THE USER MAKE SEVERAL TEST RECORDINGS TO GAIN EXPERIENCE WITH THE PROPER SETTING OF THE RECORDING VOLUME LEVEL.
10 You may now Record. To listen to the recording being made, you may, at this point, turn on the internal SPEAKER by means of the MONITOR SWITCH on the TONE CONTROL, or you may plug in an external speaker (8 to 16 ohms voice coil) or headphones at the EXTERNAL SPEAKER jack. The TONE CONTROL setting has no EFFECT WHILE recording.
11.To Record at 7.50 inches per second (for high fidelity reproduction), rotate CONTROL LEVER No. 2 to RECORD position. The tape will begin to move and you may proceed to record.
12. To record at 3.75 inches per second. FIRST depress the 3.75 SPEED CHANGE PUSHBUTTON, and while keeping this BUTTON FIRMLY DEPRESSED, ROTATE CONTROL LEVER No. 2 to RECORD POSITION. You may now proceed to record.

To Record from External Radio, Phonograph, Tape or Wire Recorder
1. The output of any radio, radio-tuner, phonograph, tape or wire recorder may be connected through a suitable cable to the RADIO - PHONOGRAPH INPUT. An output of 0.5 volts or more is required. The necessary modifications can be made by any competent radio serviceman.
2. Recording is accomplished in the same manner as described under " TO RECORD FROM MICROPHONE."

To Record from Built - In Radio (Models D - 37R, DC - 37R, LD - 37R)
a. Prepare machine for recording as under "INSTALLATION" and paragraphs 1 through 8 of "TO RECORD FROM MICROPHONE" except that microphone is not plugged in.
b. Turn on MONITOR SWITCH on TONE CONTROL.
c. Turn RADIO SWITCH TO "ON".
d. Tune in desired station, The hank of antenna wire supplied should be extended about the room or may be connected to an external antenna.
e. Adjust RECORDING VOLUME LEVEL INDICATOR (NEON BULB) by means of the VOLUME CONTROL for correct recording level, as in paragraph 9 under " TO RECORD FROM MICROPHONE " and proceed to record as described in that section.

To Record on the Second Track
Having recorded one track of an entire reel, to record on the second track merely lift the full TAKEUP reel, turn it upside down and place it on the SUPPLY REEL SPINDLE. Place the empty reel on the TAKEUP REEL SPINDLE. Re thread and continue to record as under "TO RECORD FROM MICROPHONE"

To Stop Tape
To stop Tape at any time, always operate Control Lever No. 2 FIRST to STOP TAPE position, then turn CONTROL LEVER NO. 1 to STOP TAPE Position.

To Rewind
a. Stop tape as above.
b. Put CONTROL LEVER No. 1 into REWIND POSITION.
c. Put CONTROL LEVER No. 2 into REWIND POSITION.
d. Turn VOLUME CONTROL to minimum.

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To Change Tape Speeds while Recording
1. Stop tape by operating CONTROL LEVER No. 2 only to STOP TAPE position.
2. If you were recording at 7.50 inches per second and desire to change to 3.75, FIRST depress the 3.75 SPEED CHANGE PUSHBUTTON, and, while keeping this button depressed, turn CONTROL LEVER No. 2 to RECORD position.
3. If you were recording at 3.75 inches per second, to change to 7.50 simply turn CONTROL LEVER NO. 2 back to RECORD position.

To Play Back Tape Recordings
a. Follow the procedures under " INSTALLATION " in paragraphs l through 7 of "TO RECORD FROM MICROPHONE" except that microphone is not plugged in.
NOTE: Recordings made at 3.75 inches per second MUST BE PLAYED BACK AT THE SAME SPEED, and similarly for recordings made at
7.50 inches per second.
b. Rotate CONTROL LEVER No. 1 to PLAYBACK position.
c. Rotate CONTROL LEVER No. 2 to PLAYBACK position.
d. Adjust VOLUME AND TONE CONTROLS for suitable loudness and desired tone quality.

Changing the Tape Speed or Stopping Tape during PLAYBACK is accomplished in the same thc during RECORD.

Erasing of Tape is accomplished in the same manner as recording, except that nothing is recorded. Erasing occurs automatically when RECORDING NEW MATERIAL ON TAPE WHICH WAS PREVIOUSLY USED,

SERVICE AND MAINTENANCE

Care of Tape
The storage and care of tape is important. Reels of tape should be stored where they will not be subjected to extremes of temperature and humidity. Rewind tape once before using when it has been stored 6 months or longer. It is recommended that new reel of tape be rewound once before recording.

Cleaning the Capstan and Recording Head is important after reasonable use. Dirt and slight gum deposits from the tape gradually accumulate on the re cording head and rubber capstan. The recording head and capstan may be reached for cleaning by removing the two Phillips-head screws from the RE CORD AND ERASE HEAD HOUSING and gently lifting off the housing cover. Cleaning is accomplished by means of a cloth dipped in carbon tetrachloride (obtainable from radio parts suppliers, hardware stores, drug stores, etc.)

Service
Proper care of your recorder will result in excellent service for years to come. Follow these simple rules:

NEVER OIL your recorder. Surfaces which are subject to wear are provided with oil-less bearings sealed for a lifetime operation.

THIS EQUIPMENT SHOULD BE SERVICED ONLY BY QUALIFIED TECHNICIANS. DO NOT remove the top plate of the mechanism. Doing so will VOID the warranty.

FOR BEST RESULTS: When beginning to record or playback, always use the right-hand CONTROL LEVER NO. 1 FIRST. When stopping tape, always use the left-hand CONTROL LEVER No. 2 FIRST.

MAKE SURE ALL CONTROLS ARE IN OFF POSITION BEFORE LEAVING YOUR RECORDER.

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MASCO SOUND REEL DUAL SPEED, DUAL TRACK, TAPE RECORDER RADIO TUNER

UNLESS OTHERWISE SPECIFIED ALL RESISTORS IN MEGOHMS (1/2 WATT) ALL CAPACITORS IN MICROFARADS 295121 WN