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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 15th Mar 2019, 12:45 pm   #1
cjacek2000
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Unhappy Old Betamax records audio but no picture

Hi,
I hope you guys can help me out. I can't seem to find an answer for this... I recently found a SONY SL-5000 Betamax and I spent weeks meticulously restoring, at least mechanically. All belts, idlers and pinch roller restored, properly cleaned head drum, heads, etc... Oh, and before doing anything to it, I did briefly test the VCR for all basic functions and playback and all was good. other than belt/idler related problems. The unit looked to be used very little judging by the head drum and other signs of mostly non-wear. I made a major error not to test RECORD initially due to lack of blank tape and the only tape I had the content I wanted to keep. I spent a lot of time on this and got it working fully and like new, with the exception of one thing - the RECORD function. I hooked it up first using coax in/out and then AV in/out, to eliminate one or the other as the possible issue but both ways all I got was "snow". I was able to playback (factory recorded tape) but when I got some blank (new) tape to record, all it did was record audio but not picture (it's just "snow"). I spent a lot of time trying other VCR's with the same hookup and they all worked, except this one. Some have suggested re-seating head drum connectors or other related recording circuitry connectors and / or cleaning them.. Before you suggest capacitors (not my forte) can we eliminate some other possible issues?
Much thanks in advance for your help.
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Old 15th Mar 2019, 3:04 pm   #2
TIMTAPE
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Default Re: Old Betamax records audio but no picture

Hi cjacek2000,

Is there anything resembling a picture in play pause mode or is that just random snow as well?

Tim
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Old 15th Mar 2019, 3:53 pm   #3
DangerMan
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Default Re: Old Betamax records audio but no picture

Does this model use a mechanical slider switch for record/playback changeover to the video heads? If so it might be worth attention/clean up.
Over here the SL8000 did, and this was a very common fault.

HTH Pete
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Old 15th Mar 2019, 8:33 pm   #4
dj_fivos_sak
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Default Re: Old Betamax records audio but no picture

The SL-5000 is the American version of the SL-C6. So no mechanical rec/play switches there. But it's possible there is relay that switches the heads between record and play, like on some of my Sanyo machines.

Fivos
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Old 16th Mar 2019, 1:39 am   #5
cjacek2000
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Default Re: Old Betamax records audio but no picture

Quote:
Originally Posted by TIMTAPE View Post
Is there anything resembling a picture in play pause mode or is that just random snow as well?
Tim, it's random snow as well, like playing back a blank tape. There's only sound from the recorded test. I hit pause and it's still snow.

Quote:
Originally Posted by DangerMan View Post
Does this model use a mechanical slider switch for record/playback changeover to the video heads? If so it might be worth attention/clean up.
Over here the SL8000 did, and this was a very common fault.
Pete, while it has a slider for record, I don't think it's the mechanical type. The SL-5000 is also indeed known as the SL-C6 (as Fivos pointed out). See here: https://www.palsite.com/slc6ovi.html

Quote:
Originally Posted by dj_fivos_sak View Post
The SL-5000 is the American version of the SL-C6. So no mechanical rec/play switches there. But it's possible there is relay that switches the heads between record and play, like on some of my Sanyo machines.
Yeah, will try to disassemble again (ugh) and see what I can do...
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Old 16th Mar 2019, 4:12 am   #6
TIMTAPE
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Default Re: Old Betamax records audio but no picture

Of course if it won't playback video then it's not possible to test whether it will record video as well. Are you absolutely sure the machine initially played back the pre recorded tape with both picture and sound?

Are you familiar with what healthy video heads look like? I view them under a powerful magnifier like a lupe under strong light.

Especially with certain older tapes, the tiny video heads can be easily fouled with tape material and need cleaning. Are you familiar with techniques for manually cleaning the heads with the proper materials, not cotton buds /Q tips, and only cleaning in the horizontal direction?
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Old 16th Mar 2019, 2:02 pm   #7
cjacek2000
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Default Re: Old Betamax records audio but no picture

It does playback the factory prerecorded tapes no problem. I am sure. It is only the recording of video that is the issue.

While I do know what healthy heads look like and am meticulous at properly cleaning the entire tape path (video heads/cylinder carefully using strips of plain white paper soaked in 99% alcohol and indeed using the horizontal direction), I will try to clean once more and try recording again on new virgin well known to be good tape and will report back on my findings.

Thanks again for your input.
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Old 16th Mar 2019, 6:59 pm   #8
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Default Re: Old Betamax records audio but no picture

Unfortunately nothing's changed. I cleaned the heads again (no visible dirt "tracks" on the alcohol moistened paper) and heads look clean as a whistle. I inserted a new virgin BASF tape, pressed record, recording started. I then played back what I attempted to record. Only sound was recorded, no picture, "snow", like it never even recorded any image whatsoever. It's like somebody completely disconnected the ability to record video. That's how it plays back. The factory prerecorded tape, however, plays back fine, no issue...
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Old 16th Mar 2019, 9:36 pm   #9
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Default Re: Old Betamax records audio but no picture

Just a thought ..... It might be worth checking if the erase head (a) has continuity and (b) is getting any power in record mode? Because that's something that is both different between recording and playback, and would affect the picture more severely than the sound .....

The sound head in a VCR has to record onto tape that has already had a bit of (unnecessary; the other head still hasn't reached the top of the tape by this stage) picture signal recorded on it, so it puts out enough magnetism to obliterate whatever was there before all by itself. But the video heads can't put out too strong a field, because the lines of flux have a natural tendency to go wide of the head and the diagonal tracks have to be very close together with no guard band between them (a special trick is used to simulate a guard band on playback). It doesn't matter about the sound track going a bit wide; since there is still room designed into the system for a bit of a guard band above it, and on the bottom side there is no tape, just thin air.

If it was trying to record a video signal over the top of another video signal and some of the original is still there for want of erase head functionality, that could cause all manner of problems .....

If you have no way to test the erase head voltage, can you listen for any breakthrough of old audio?
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Old 17th Mar 2019, 3:22 am   #10
cjacek2000
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Default Re: Old Betamax records audio but no picture

Thanks Julie. I will check as you suggest. I want to add that I put in a tape (with previously recorded material) inside the machine, put it into record and while it did not record any new material, it did manage to erase part of the tape (the section that I recorded on), meaning that the machine did go into "record" but only managed to erase and not record anything new. So the question is what would cause a machine to perfectly playback (factory recorded tapes) but not record any new video material (only erase) but only record audio? You did in fact mention the erase head possible issue. I have a voltmeter and sorry to ask but how would I measure it correctly? And would it make any sense if I re-sat and cleaned the plug-in cable or connector (for the erase head) or is that a waste of time? Thanks.
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Old 17th Mar 2019, 5:49 pm   #11
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Default Re: Old Betamax records audio but no picture

I have virtually no Betamax experience but lots with VHS and to me this sounds like there is no FM video signal being fed to the heads in record mode.

What test equipment do you have? a scope would be ideal. I can't find a manual for the SL-5000 but if it is a close relative to the SL-C6 as Fivos suggests then looking at the manual for that model there are several fusible resistors that could possibly cause this fault, these could be checked with just a multimeter. The manual for the SL-C6 can be downloaded here

John.
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Old 19th Mar 2019, 12:20 am   #12
cjacek2000
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Default Re: Old Betamax records audio but no picture

John, thank you very much for your response and info. I do have that PDF manual but thanks anyway for searching it out for me. I do have a Mastercraft Multimeter (model 052-0060-2) and also a pretty cool little ESR meter. Although I'm very new to this electronic side of things. Mechanical no problem but electrical, no so much.. Anyway, the components you mention, are these on the PCB board section labeled "REC AMP"? I've made a screen shot of a section of this board, attached.
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Old 19th Mar 2019, 8:43 pm   #13
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Default Re: Old Betamax records audio but no picture

Hi Cjacek, that's a good place to start. First of all set the machine to record then measure the voltage at TP1, there should be around 10V DC here. If it's missing check at CN8001 pin4, if there is 12V here then fusible resistor R36 8.2Ω is likely to be o/c. Another fusible to check on this board is R47 82Ω.

If these check ok and the voltage is correct at TP1 in record head over to the main YC18 board and check R43 100Ω.

Good luck.

John.
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Old 20th Mar 2019, 6:26 pm   #14
cjacek2000
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Default Re: Old Betamax records audio but no picture

Thank you John. I will open 'er up and follow your instructions. Will report back. Might take some time though 'cause I'm also learning while I go and I wanna go slow, make sure I do it right.. Thanks again.
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Old 20th Mar 2019, 9:25 pm   #15
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Default Re: Old Betamax records audio but no picture

Take it slow, steady and in your own time, before taking resistance readings leave unplugged for at least 30 seconds.

John.
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Old 20th Mar 2019, 10:37 pm   #16
cjacek2000
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Default Re: Old Betamax records audio but no picture

With the ESR meter you mean? Yeah, I'll have the VCR unplugged for sure. The multi-meter on the other hand I'll have the VCR in record as you suggest (plugged in) testing those points you mention. Will take it slow, and will read up on what I'm doing to make sure I do it correctly. Thanks again.
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Old 20th Mar 2019, 10:59 pm   #17
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Default Re: Old Betamax records audio but no picture

No, the ESR meter is normally used for measuring electrolytic capacitors. Use your multimeter switched to Ohms for the resistors.
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Old 21st Mar 2019, 12:31 am   #18
cjacek2000
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Default Re: Old Betamax records audio but no picture

oops, alright, thank you.
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