Panasonic AG7350 Noise issue

hodgey · #1 03-14-2019, 09:26 AM

Trying to see if I can fix up this old beast.

There is some noise that is not supposed to be there, especially noticeable when paused (start of clip) on top of the image. There is some pattern over the whole picture.

ag7350 prob 1 cut.avi

I thinking it may be bad caps somewhere, but I don't knw where to start looking. Haven't seen any visible issues on the circuit boards. It works great otherwise, Hi-Fi audio sounds fine so I don't think there are issues with the heads. We got 2 of these machines, both seem to have the same issue, though one also has some colour interference as well.

Would one normally replace ceramics capacitors when recapping VCRs (not just specifically this model, have others that I'm considering doing some replacements on), or just electrolytics?

Also wondering if anyone has experience with how to disconnect the "ribbon" cable connectors on these types of boards? They don't seem to come off easily and I don't want to risk breaking them.

ofesad · #2 03-14-2019, 04:37 PM

I dont see any noticeable noise at the top of the image. Or you mean on top? (the flickering)

This could be solved in post-production with filters.

It could be a lot of things, the easy ones:

* RF interferance. Some VCR's are very sensitive and should be used only with the cover on. Also a proper ground is needed.

* Luminance noise also is related to the heads. If one of the heads is going bad or dirty could cause this.

I suppose you are using an external TBC? the AG7350 does not have a built in TBC.

Do you have a multimeter or a ESR meter for checking the caps?
Ceramics and mylar, rarely go bad. It could, but the most common cause of issues is eletrolitic and the surface mounted are the worse.

With a multimeter you can measure non-polarized caps, however the best tool for the job is the ESR meter or "capacheck" like somes call it.

Ribbon cables usually have 2 types of connectors, the first the ones you just push it in/out the ribbon cable. And the others you have to lift the top part of the connector so it will release the ribbon cable.