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Crumbtrail TV Forums: TV Equipment: VCR Repair Forum:
Sony Betamax SL-C7/SL-C7UB



New User

May 20, 2016, 9:58 AM

Post #1 of 3 (12016 views)
Sony Betamax SL-C7/SL-C7UB Can't Post

A few years back I picked up a job lot of old VCR's off of ebay. It included two Sony Betamax VCRs - a SL-C7 and SL-C7UB. One of the VCR's works (but has a problem which I will explain below) The other one doesn't work but I figure it can be used for spare parts as the machines appear to be identical internally.

On the functioning Betamax, everything appears to work; however, when I play anything the picture has a band of noise on it that roles horizontally every few seconds. It's as if the drum is spinning faster than the tape is moving or vice versa.

I figure it has some issue reading the pulses from the control track on the tape that fine tune the tape speed; so, the tape speed doesn't match the drum speed and this is what is causing the horizontal noise bands.

Even if I record on the machine and playback the issue remains so I don't think it can be anything to do with head misalignment/tracking.

Any clues on what it could be or what I should replace from the donor machine?

Cheers :)

New User

Nov 12, 2016, 7:56 PM

Post #2 of 3 (6395 views)
Re: [TheGMan] Sony Betamax SL-C7/SL-C7UB [In reply to] Can't Post

i would usually think that this could be caused by faulty capacitors in the power supply.

If the rest of the picture isn't distorted, i wouldn't think about drum speed.
Might be wrong ofcourse :-)

If you check all PSU output voltages with ossciloscope, are they nice and steady?
Everything should be fixable :-)


Nov 14, 2016, 10:32 AM

Post #3 of 3 (6191 views)
Re: [bungieke] Sony Betamax SL-C7/SL-C7UB [In reply to] Can't Post

You are correct, it sounds like is not reading or recording pulses.
The usual is the small sound head. This not only does sound, but at the bottom of it, it picks up a sync pulse.
The machine picks up the pulse on the main head and on the sound head to regulate the speed. The head may be dirty worn or misaligned. A tip here is clean the head with Silvo. Use this as a When all else fails head cleaner.


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