Diagonal lines or audio buzz, bad caps?
 

Hi!
I have issues with a DVD-VHS Combo from 2003. I cleaned the VCR heads but the problem still remains.
I tried several tapes and depending on the tape it's either diagonal lines running across the screen while the audio is fine OR irregular audio buzz with no or very slight diagonal lines. The DVD section doesn't have any of this. I already tried connecting it in a different room to a different TV. Could this be capacitor related or should I look somewhere else?

Video issue: https://youtu.be/ic-tzwwn54A
Audio issue: https://youtu.be/9H_WIdiZjOM
(the horizontal flicker is from the phone recording)

That's quite possible. Bad power supply caps that don't filter as well as they should can for instance result in some form of periodic noise. I've seen it cause more wavy/large horizontal lines, but this could be similar.

Bad caps is less likely than simple dirty power. Are you using a UPS with AVR?

Thanks guys. I don't use a UPS. I have a regular VCR that doesn't show any of these symptoms if I hook it up the same way. Also, if this is power or power supply related, shouldn't there be interference in the menu as well as during DVD playback? I'm just wondering if I should change caps in the whole unit or just the power supply / VCR section.

Then that's a likely issue.

Doesn't matter. All devices can act differently. It depends on how the power supply is made, all shieldings, etc.

Not necessarily, no.

You've never mentioned what you have, model/make. Caps may not be likely. Only replaces caps that are known bad, or known to be bad in the future (due to model/make of unit).

On the mentioned combo deck I had with bad PS caps, it impacted the DVD-side as well though it was a fair bit less noticeable and it was more a brightness fluctuation than moving bars. It's the large filter capacitors on the secondary side of the power supply (right after the transformer in the circuit) that are most prone to go bad as they have a lot of current and head affecting them, and when they go bad they don't filter the oscillating voltage levels coming out of the transformer enough and you get issues. Caps in the VCR part don't go bad as often unless they were a bit dodgy from the factory or there were design flaws, which was something you saw more on older early 90s vcrs like the Panasonic AG1980P.

One indication of it being capacitors as opposed to a different issue is if the issue appear after being powered on a while (or only appearing after being on a while) since they are affected by temperature.

I have seen interference that looked more similar to the one on your picture on two Sony VCRs I got, though it's much more faint and only visible on LP tapes.

One quick thing you can try, is to turn off the RF modulator in the VCR menus if it's available on this model (on many you can only change the channel), which may or may not help much.

Thanks for the great explanations guys! :thumb:

I don't think anyone here ever heard of a Medion MD41558. It's a rather inexpensive German brand. I can't really do anything about the possible dirty power situation right now. I know that I had some interferences in audio eqipment in one room and none in others. So I tested the combo in different rooms which had no effect on the severity of the issue. So I don't think it's that but obviously I can't say for sure.

The problem appears right from the start. I have the impression that it gets a little bit better after a while but not much. Can't do anything about the RF modulator. This unit actually has two power supplies inside, one for the DVD and one for the VCR.

Anyway, I just ordered an ESR meter that lets you test caps within the circuit so that should save me some unnecessary desoldering.

I've heard of the brand at least, it's probably made by Funai, LG, Daewoo or some other VCR manufacturer that were still around at the time though.

Medion is mostly rebadger brand like Tevion. And what they tend to rebadge is whatever is cheapest. They just take goods sold in Asia and North America, and it's a Medion in Europe.

Medion rebadged everything from LiteOn DVD recorders to Easycaps.

This deck is going to be low quality, whatever it is inside.