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Sony SL-810D Beta VCR

I service beta VCR's for resale, and right now I've got a Sony SL-810D that's driving me up the wall. When I acquired it, it was totally dead. Replacing the STK regulator on the power supply got it going, but the tape would only operate in reverse (even when it was supposed to be playing normally) and was also going way too fast. I replaced the capstan motor with a known-good one, this restored the correct bi-directional function, but the speed issue remains. When in normal playback mode, the tape runs at near fast-forward speed. When in slow-mo, it runs at just above normal playback speed. Pause, fast forward, and rewind work normally. The capstan free speed adjust potentiometer does have some effect, but doesn't bring the speed anywhere near within range. The problem is present both during playback and record, and it correctly senses BII or BIII recordings, ruling out any issues with the A/C head or associated circuitry. I've spent countless hours pouring over the service diagrams, and have swapped numerous IC's from the ST-18 board with known-good ones from another VCR, all to no avail. I've also checked all the caps in that area for ESR. Without a thorough knowledge of VCR design, all I can do at this point is swap parts. I thought I had enough skill, but I cannot grasp enough of this particular circuit design to effectively troubleshoot the problem. A good place to start would be knowing where to find the reference voltage or signal that determines the overall capstan speed. Can anyone give me any ideas, or better yet, does anyone have another one of these units for parts?

Reply to
Chris F.
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Does the service manual show waveforms? Try checking those. This might narrow down the problem.

Also, given the unit's presumed age, look for something electrical, rather than electronic -- bad board or cable connections.

By the way, it's pore, not pour.

Reply to
William Sommerwerck

Hi Chris,

Some basic things to check: Is the pinch roller engaging properly? Is the capstan motor actually moving the tape or is it getting some help by perhaps a take up motor or clutch that has too much torque? Try and add some drag to the pinch roller by squeezing it gently with your fingers. If that doesn't slow it down, then the tape is being pulled by the take up motor instead of being locked into the speed of the capstan motor. If the capstan motor really is turning too fast, you're going to have to figure out the servo control system. Or another approach is to just give the circuit boards a good visual check. A bad connection or cold solder joint could cause some strange things to happen. Does tapping on any of the boards have any effect on the speed?

Good luck.

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David Farber
Los Osos, CA
Reply to
David Farber

Is there actually a market for Beta VCR's? I never would have guessed that. Dave

Reply to
dav1936531

I know I still use Beta, have a big library of tapes and a couple of working Beta VCRs. Heck, there's still a market for RCA "needlevision" CED videodisc:

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Reply to
Roger Blake

Turns out the capstan motor I subbed was not quite the same, and had a different hall effect IC for the FG circuit. I managed to swap the IC from the old capstan and that appears to have corrected the problem. Another lesson learned......

Reply to
Chris F.

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Thanks for letting us know the fix

Reply to
hrhofmann

Seen bad tracking potentiometers on some Sony Beta decks - the center tap opens up. Cleaning doesn't help, since the tap is actually broken away from its holder. Some other Sony decks, like the SL-5000 had capacitor issues in the servo circuits - there was a kit sold for those.

Mark Z.

Reply to
Mark Zacharias

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FWIW - The cap kits for the SL-5000s are still available. Installed a kit a few weeks ago.

Dan

Reply to
abrsvc

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