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Quick fault guide overview
Sony 1983
Betamax SL-C30



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711B CHASSIS

Technical


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Pendulum

Stops in play or record

This is becoming a more common problem these days. The first thing to check is that there is adequate torque on the take up spool. If there isn't much then the cause is usually down to two contributing factors.

The first is the drive pendulum which can cease up and the second more serious factor, is wear on the reel motor bottom bearing. The pendulum is simple to replace but the bearing is moulded into the chassis and replacement necessitates that the entire chassis be replaced. One possible compromise is to fit a small piece of plastic into the bottom bearing to raise the rotor and allow it to move freely. Sony supply a repair kit for this purpose.

The repair is as follows: you remove the rotor. Then drop the shim (or small ball bearing) into the hole where the spindle fits. Next you take a file to the bottom of the spindle and gently grind it down until the stator (electro magnets) and rotor (permanent magnets) gap is correct again. This can be tested by spinning the rotor gently with one finger. The rotor should make 3 or more complete rotations with a gentle push.

There's no need to remove the motor pcb. The bearing is integral to the chassis and nothing is gained by removing the pcb. To remove the rotor you just pull. You need to do so strongly and evenly so that you have no sideways movement.

The diagram above shows the pendulum assembly

Stops in play, record and reverse/forward wind

Do not confuse this with the above symptoms. The problem in this case is due to lack of 4.43MHz colour sub-carrier reference in the servo circuit. This in turn is normally caused by failure of silicon fuse PS1 on the YC-25 board.

Patterning on picture

If you experience a patterning on the picture irrespective of whether you are viewing a tape or not then the most likely cause is that capacitor C319 in the power supply has dried up.
hall effect sensors with glue
Hall effect sensor attached with glue

No head drum rotation

You may find that the head drum fails to rotate. This is due to a problem with the Hall effect device on the head drum motor which is secured by a blob of glue. Full details on how to fix this can be found on the head motor page.

Deck goes into rewind

This can be caused by failure of the tape end sensor. You can check this by unplugging the sensor at its socket on the PCB.


Quick fault guide

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FaultSolution
Damaging tapes or tape looping during ejectCheck resistor R420 (3.3ohms) then transistor Q334 (2SC10613).
Insufficient or excessive colour in playbackCheck resistor R019 (56Kohms) on panel YC25.
Intermittently will not eject-cassetteCheck connector CN608 on the SS16 panel for a poor contact.
No capstan servo lock in recordSuspect failure of transistor Q332 (2SC2458) on panel SS16.
No colourCheck the value of resistors R024 (56k ohms) and R278 (10k ohms) before suspecting capacitor C047, all on the YC25 panel.
No E-E picture after 15 seconds, records in black and whiteAdjust RV009 for 4.3volts p-p at C104 on panel YC25.
No functions or displayCheck IC001 on the TP37 board
No play, FF or cueSuspect failure of the forward sensor.
No take up / chewing tapesCheck condition and positioning of the pinch roller.
Not erasing previous recordingsCheck for failure of Q503, Q501 (2SA8811) then Q502 (2SC24581)
On/standby switch inoperative, corrupt displayCheck diode D001 on the TM37 panel.
Program display showing -au-Check resistors R063 (120Kohms) and R073 (4.7ohms) before suspecting failure of IC003 on panel TU39
Stopping in rewind / review modeSuspect failure of transistor 0606 (2SC2458) on panel SS16
Switches off shortly after switch onCheck PSU. regulator IC401 (STR1229) on the PS23 panel
Will not eject cassettes, pinch solenoid not operatingCheck resistor R654 on panel S516
Will not tuneCheck for failure of IC004 on the TU39 board before suspecting the pre-set unit PS001 of failure
Intermittent squiggly patterningPattern is very similar to that caused by C319, but NOT applying to E-E loopthrough. Check Delay Line DL001 on video PCB.
Cassette jams before loaded properly (mentioned in text above)The load arms go out of alignment under tension causing the jam due to failure of the left hand side gear which splits at the D section hole. Remove the assembly, fit a 7mm shim to the outside round of the white gear centre, realign the assembly and refit it to the machine.
Electrical tracking way off centre positionReplace C316 (0.22uF light blue Sanyo electrolytic capacitor)
If you have an oscilloscope perform adjustment as per service manual to achieve 7mS delay between the pulse monitored at TP405 and TP406
Will not load tapeLoad motor has jammed in centre of planetary gear due to a combination of corrosion and the lubricant drying up.
Remove planetary gear clean metal drive shaft. Clean out centre hole of black plastic planetary gear base with a 4.5mm drill by rubbing it in and out through the hole to remove dried lubricant. Apply a light coating of grease to shaft and gears and reassemble.
Speed or torque varies on spools (both playback and winding)If the bearing and pendulum are ok and you still are experiencing speed or torque variations at the spool motor check the four 47uf/16V miniature electrolytics on the motor PCB. Clean the pcb, replace all four caps and check the traces for damage.
Slow in forward and or reverseAlso sudden drops in the winding speed and the tape tension didn't seem right sometimes in playback. Take a look at the four capacitors on the spool motor PCB. Check the four miniature 47uf/16V capacitors (Matsushita) to see if they are leaking. Clean the PCB and install new capacitors.
Unswitched 12V from power supply way to highCheck if voltage on pin 7 of CN304 is 12VDC +-0.5V. If it's way too high (14V or higher) check transistor Q309 (2SC2785 NPN).
Fluttering audio after press, REW and FFWD with picture searchCheck for worn out tension band.
Replace the tension band,
and re-adjust the back tension.
Cassette will be accepted and ejects but tape will not loadCheck the position of the microswitch and notch next to the videodrum in the upper left corner of the deck.
Display will only say AV or switches between tuner and AV randomlyClean the LINE-TUNER switch on the front panel with contact cleaner 390.
Soft white noise in audio and random dimming of displayCheck all the small value (under 220uf) electrolytics on the PSU boards for leakage around the legs and replace.
No Record or E-ENo Record or E-E, playback O.K. Check for Dry joints on Q715 and Q716 RP7 Board.
Poor rewindThis can be due to the internal thermal fuse failing in the brake solenoid.
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