Betamax SL-C6

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Fault and repair guide

SL-C6ES rear view
SL-C6ES rear view

SL-C6ES rear connectors
Rear connectors
220/240V selector, linear stereo audio in/out
TV din connector

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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No powercheck the power regulator IC001 [STK5314] for failure
Dead, fuse F002 blownCheck diodes D301-304 for failure
Dead, fuse F001 blownCheck diodes D305-308 for failure
Distorted sound on all channelsSuspect failure of Q009 [[email protected]] on the tuner/IF. board
Drum speed variationReplace 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 unlaceReplace belts then the small relay pulley, large relay pulley and the phosphor bronze bearing between the two relay pulley,
No or erratic drum motor operationCheck 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 soundCheck the contacts of relay RY1 on the ADG panel for wear sticking. If fault persists check diode D001 for failure
No capstan motor rotationCheck transistor Q022 [2SDI164] on the DR1 board for failure. If ok check the servo chip [CX143A]
No colour in pause, incorrect colour in picture searchCheck capacitors C084 & C083 on panel YC18 for failure
No e-e signalsCheck transistor Q01 for failure
No fast forwardCheck transistor Q025 [2SD1164] on the DR1 board and also check 0023 [2SD788] Q024 [2SC2785] for failure
No neon channel indicators, no channel selectionCheck R015 on the power panel for open circuit.
No reel motor operationCheck R061 on the DR1 board then suspect Q010 [2SD3553]
Not erasing previous recordingsCheck transistor Q1 [2SD774] & resistor R025 on the AD6 board
Noisy pictureCheck capacitors C016, C018 & chip IC001 for failure.
Poor sound on one channel and associated neon indicator dimReplace the appropriate channel indicators neon lamp
Tuning driftCheck tuning voltage regulator IC002 [UPC574J] for failure.
Intermittent or no rewindCheck connector CN606 on panel DR-01 for poor contact.
No loading motor drive voltage or operationCheck fusible resistor R665 on the DR-01 board for open circuit.
No E-E sound, no capstan lock on playbackQ509 (2SA1175) short circuit.
power supply failureif 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.
Clock Powers up but no power to rest of machine when on/standby pressedFailure of the Transistor Q255 and/or Diode D251 on the TP-12 power board. This circuit provides power to the on/standby.timer switches and leds an then the switches switch the regulator to power the 12 regulated lines on multiple boards. See Page 42 of the service manual http://www.beta7.co.uk/uploaded/documents/sl-c6e-sm.pdf
Slow Capstan Speed and RV1 cannot increase the speed far enoughReplace 0.22uF caps on SS9 board (Capstan Area) position C7 and C8
Playback runs at right speed but recordings run slow with noisebarsGive the audio/control (ACE) heads a thorough clean. Use isopropynol and a reasonable amount of pressure as the control head in the assembly has fine in-grained dirt which causes the control track to not produce enough signal to lock on to.
Using a cotton bud keep on cleaning even if the buds look clean. Use enough fluid on the bud to soak it. Leave the machine for about 5 minutes to allow the fluid to evaporate.
Slow sound & rolling pictureCorrected capstan speed & reel by slight adjustments to RV1 & RV2 then RV9 (on SS9 board underside) whilst watching monitor.

This should be done with a scope following manual, but this worked well enough as only using own tapes on it.

You need to remove the base plate & let VCR end overhang stand to allow screwdriver access. (If new to working on VCR's most is 12 volts BUT avoid high voltage transformer area contact where mains cable goes to!) Turn with insulated screwdriver in slot a little, if worse on screen turn other way, only about 5% turns, whilst playing tape & keep level.
(Make a note of original positions of RV's before turning!

No rf output to tv green play light on always even with no tape inRibbon cables onto ss9 board broken or dry joints resoilder

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