2 system 80 problems

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2 system 80 problems

Postby matsondawson on Wed Aug 28, 2013 7:14 pm

The system-80 I am keeping from the haul has 2 issues.
1/ The video is poorly. The screen wobbles up and down with a period of about 1 second. Causing TV to lose lock.
2/ The tape drive rewind is reeeeally slow, if at all. Yet fast forward and play work fine.

Anyone got any ideas?
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Re: 2 system 80 problems

Postby tezza on Thu Aug 29, 2013 12:14 am

Re the video.

Could be caps in the PSU. They do cause this kind of problem. Have you tried swapping the PSUs between the 2 machines you have. See if that improves it. There are other things that can cause this too. I did fix a machine that had this issue that WASN'T due to the PSU but I'd have to dig out some notes on what I did.

Have you downloaded the technical manual from the System, 80 site. That has some troubleshooting notes in it.

As for the cassette deck, that is very typical. Weak motor going backwards. Not sure what causes it but nearly every S80 I've come across has the same problem.
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Re: 2 system 80 problems

Postby RonTurner on Thu Dec 26, 2013 11:57 pm

My video genie also has slow rewind same as yours so makes me think it might be a common issue ?

I also had poorly RF video, both the Video Genie and System-80 where identical while trying to tune
the TV set, just a fraction either way and the picture would role and characters would "wobble" sideways
no matter what ! luckily these computers have Composite video, this was unaffected and crystal clear.
Last edited by RonTurner on Sat Jan 04, 2014 6:31 pm, edited 1 time in total.
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Re: 2 system 80 problems

Postby tezza on Fri Dec 27, 2013 7:01 am

That wavy video problem. I said I had that problem once that WASN'T PSU caps. I can also be caused by a faulty power transistor on the board itself. See
http://www.classic-computers.org.nz/blo ... en-fix.htm.
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Re: 2 system 80 problems

Postby RonTurner on Fri Dec 27, 2013 8:49 am

That's interesting maybe my system 80 has that same issue ; composite video is perfect but RF the top of the characters are swaying about the place
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Re: 2 system 80 problems

Postby tezza on Fri Dec 27, 2013 9:30 am

RonTurner wrote:That's interesting maybe my system 80 has that same issue ; composite video is perfect but RF the top of the characters are swaying about the place


Well, in both cases where I've had to deal with swaying text, the screen was connected via composite video. So it wasn't an RF issue. RF is inherently more unstable and relies on just how good the tuner in the TV is too, of course. For the best image, I always connect my System 80s up using composite video. In some of the System 80s I've bought, the previous owner has removed the RF cable entirely (and one one occasion the entire RF modulator).
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