JVC HR-S6800U playback issue, recording is fine?

[theugster]

Howdy all!

I just picked this VCR up super cheap from a local seller figuring I'd tinker on it and learn a few things. I've come across a very strange set of issues with it that I'm scratching my head on now. Mechanically the unit seems completely fine, loads the tape, spools, all functions work perfectly.

The original issue was that, nine times out of ten, loading and playing the tape would show a distorted/heavy tracking issue picture and bad sound. One out of those ten times though, the tape played back perfectly, video and audio. I dug into this and discovered that an SMD capacitor on the head drum circuit board could be responsible and sure enough, it was measuring a dead short.

After replacing this capacitor, I got a much better result in that I get a stable (mostly) picture. However, I'm now seeing consistent, very heavy horizontal color comets and interference on tape playback. I've attempted to perform some very basic roller guide adjustments, but that didn't improve things at all and I've probably just made more work for myself in calibration later on.

The weirdest part of this is that the blue screen menus and pass-through video sources show up perfectly clearly with no distortion at all, and when I *record* to a tape from this unit and play it back in a different, working VCR, the recording looks fantastic.

I'm sort of at a loss here and any advice would be much appreciated. I ordered a couple of PSU caps as those seem to be on their way out anyway, but I'm not optimistic that those caps are my smoking gun here.

Thanks in advance!

EDIT: Took a quick video of the tape loading, as well as the issue I'm dealing with. The camera picked up some extra tracking artifacting that I wasn't seeing, the main issue I see on-screen is the horizontal color comets and flagging picture - https://www.youtube.com/watch?v=EdOL9utkeKw

[hodgey]

On my PAL HR-S5800 there were some bad caps in the power supply and hi-fi module (SMD electrolytics), and the video module also had some SMD electrolytics which may or may not have also been bad. Before swapping I had a lot of audio whine. I swapped those which fixed it but it randomly developed some servo issue instead. Not sure how similar the NTSC variants are though but bad power supply caps wouldn't be surprising. If not that maybe some grounding issue, though it looks like it could be after the head amp stage so not sure.

[theugster]

Awesome, thanks for the reply!

Do you happen to remember which caps you replaced on the video board? I was able to track down a service manual/schematic for this model but I haven't dug too deeply into it yet. Currently waiting on an ESR meter so I can spend less time guessing on which parts may be at fault here. For what it's worth, I don't see any clear signs of electrolytic leakage on the video board, in fact nothing stands out to me at all on that board, it's only the power supply that had the leaky caps and corrosion.

Thanks again, really want to bring this thing back to life and keep it out of the dumpster!

EDIT: Added a picture of the PSU board corrosion, as well as the head drum capacitor I replaced.

[hodgey]

Ah, I expected the 5800U and 6800U to be based on the same base like is the case with the PAL 5800 and 6800 but now looking at the SM for the 6800U seems that might not be the case and the 6800U is more different than I thought so might not be too much of help here.

I replaced all the surface mount electrolytics on the "hybrid IC" (it's like 2 pcbs glued together or something in this case) on the video board though the NTSC ones don't seem to have used one of those for the video part and only the 5800U used one for hi-fi so SMD electrolytic caps might not have been used in the 6800 other than the one under the head drum on all units with this mechanism.

[theugster]

Fiddled around a bit more today, I took another look at the corroded traces on the power supply. I checked resistance across those paths and all of the connections checked out, but I may end up running some wire across the particularly nasty bits.

I've attached a video that better shows the distortion/artifacting I'm seeing with this unit.

Starting to think damaged or worn head now. Since I replaced the head drum cap and handful of PSU electrolytics, I'm not able to reproduce the "1 in 10" good picture, which is very strange indeed.

[latreche34]

How can it be the heads when you stated it records fine? If this is a playback issue only, it will be somewhere in the playback head preamp.

[lordsmurf]

Normal required question = Is it worth fixing? And with the 6800, not really, too old.

But you stated this right away: "I just picked this VCR up super cheap from a local seller figuring I'd tinker on it and learn a few things."

So carry on. Just needed to point this out for anybody else that may find the thread. 6800 not really good, not really suggested, ancient S-VHS model. But for learning, go for it!

[theugster]

Thanks for the assistance and guidance, everyone. Much appreciated throughout this process!

I finally did sort the issue out, albeit entirely accidentally. I went through the effort of tearing the power supply down to replace capacitors. In order to do that on these models, you have to de-solder the board from the metal enclosure (I think Sony did this at some point too!) in addition to a half dozen screws.

The reason this matters is that, while testing on the bench, I didn't put the power supply back in this enclosure, and the lack of shielding and close proximity of the power supply to the drum pre-amp caused the interference you saw in the video. In my attempts to not electrocute myself, I made sure not to touch the power supply while it was powered on. This time I'd had it tilted up and out of the way for a testing cycle and the picture was perfect.

So all in all I have about $10 in capacitors and way too much time invested, but it's otherwise working perfectly and has a great picture. I may go back and fine tune/readjust things later but it's now a fine addition to my obsolete tech stack.

Lessons learned: Unsure, but shielding sure is important.