Betamax PALsite: SL-C6 : Technical

SL-C6

1982

Technical

Fault and repair guide

VCR is sluggish in or fails to rewind

Internally the VCR contains many drive belts which are used in the mechanics of tape transport. With age these belts become slack causing malfunctions and when this happens the whole lot should be replaced. In particular for the rewind function you will need to replace a tyre on the supply reel. A 'rewind' kit of replacement parts is available from many sources.
The diagram shows the rewind spool

Poor capstan lock

This causes a noise bar to appear on the picture and a wow on the sound. The first thing to check is the CTL head. If it is clean and not excessively worn then the next thing to do is to re-adjust the capstan free-run speed. This is done by adjusting RV001 on the servo board. You need to adjust until you read 5.5 +/- 0.3 V on test point TP5. If it is not possible to get a steady reading then there is a problem in the servo circuitary which is most likely caused by dried out electrolytic capacitors. Suspect C7 and C8 first but if in doubt replace all the capacitors on that area on the board.

Horizontal noise bar across bottom of recored pictures

This comes about because the record servo lock adjustment drifts. What you are actually seeing is the head switching pulse on the picture. It should be hidden from view in the frame blanking period. To reset this adjustment really requires an oscilloscope but if like then you can try it by eye. The adjustments are made through RV8 on the SS-9 board.

Quick fault guide

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Fault Solution

No power. check the power regulator IC001 [STK5314] for failure

Dead, fuse F002 blown. Check diodes D301-304 for failure

Dead, fuse F001 blown. Check diodes D305-308 for failure

Distorted sound on all channels. Suspect failure of Q009 [2S@11753] on the tuner/IF. board

Drum speed variation. Replace the small electrolytics around the drum servo chip C3 [CX1861 also check the drum free preset RV9 if OK check resistors R103, R106 & Rl1O before suspecting 1C3 itself

Intermittently stopping / fails to unlace. Replace belts then the small relay pulley, large relay pulley and the phosphor bronze bearing between the two relay pulley,

No or erratic drum motor operation. Check resistors R045 a R060 on the DR1 board for open circuit then Q017/18 [2SC27853] Q019 [125A1175], Q020 [2SC1061] and Q021 [2SD1164]

No or poor sound. Check the contacts of relay RY1 on the ADG panel for wear sticking. If fault persists check diode D001 for failure

No capstan motor rotation. Check transistor Q022 [2SDI164] on the DR1 board for failure. If ok check the servo chip [CX143A]

No colour in pause, incorrect colour in picture search. Check capacitors C084 & C083 on panel YC18 for failure

No e-e signals. Check transistor Q01 for failure

No fast forward. Check transistor Q025 [2SD1164] on the DR1 board and also check 0023 [2SD788] Q024 [2SC2785] for failure

No neon channel indicators, no channel selection. Check R015 on the power panel for open circuit.

No reel motor operation. Check R061 on the DR1 board then suspect Q010 [2SD3553]

Not erasing previous recordings. Check transistor Q1 [2SD774] & resistor R025 on the AD6 board

Noisy picture. Check capacitors C016, C018 & chip IC001 for failure.

Poor sound on one channel and associated neon indicator dim. Replace the appropriate channel indicators neon lamp

Tuning drift. Check tuning voltage regulator IC002 [UPC574J] for failure.

Intermittent or no rewind. Check connector CN606 on panel DR-01 for poor contact.

No loading motor drive voltage or operation. Check fusible resistor R665 on the DR-01 board for open circuit.

No E-E sound, no capstan lock on playback Q509 (2SA1175) short circuit.

power supply failure if this happens, do not expect that the power supply board from a MK1 will replace that of a MK2, and visa versa, as there are differances in the wiring, also, the MK1 is hard wired, and the MK2 the wiring has plugs to connect to the board.

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