Sony KV-20FV12 Jail Bars HELP

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OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Sony KV-20FV12 Jail Bars HELP

Post by OrdinaryCyborg »

After successfully RGB modding this KV-20FV12, I'm now trying to tackle this jail bar issue. Quick rundown- These bars are faint but definitely noticeable. They exist on all inputs and not just on the RGB mod, the bars move with HSIZE but NOT with position adjustments, G2 adjustments on flyback make NO change. Please note the photo was brightened a bit so it easier to see. The tv is actually displaying a dark grey.

This tv also seems to suffer from terrible grounding issues. Audio coming from the internal amp had a definite 60hz ground loop hum. I said "did" because while messing about, the amp died. No idea what I did but I replaced it with a new old stock amp and that one won't work either now.

Also, the video shows noticeable noise in with dark colors. Its the same noise RetroRGB Bob saw on his TV in the "RGB modding a Sony CRT for Retro Gaming". I also move my ground close to the jungle chip but like I said, its still there but noticeable on dark colors. There has to be a bad ground somewhere.

Image
https://imgur.com/a/jNMexny
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matt
Posts: 567
Joined: Mon May 09, 2005 5:46 am
Location: Honolulu, Hawaii

Re: Sony KV-20FV12 Jail Bars HELP

Post by matt »

This is a common Trinitron issue. It's caused by a bad filter capacitor on the B+ side of the flyback. There are a handful of caps that could be responsible; replacing them should fix it.
OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Re: Sony KV-20FV12 Jail Bars HELP

Post by OrdinaryCyborg »

matt wrote:This is a common Trinitron issue. It's caused by a bad filter capacitor on the B+ side of the flyback. There are a handful of caps that could be responsible; replacing them should fix it.
Sorry, I completely forgot to mention that I replaced all the electrolytic caps already with long life Nichicons. After recapping, the issue didn't change. Maybe I used one with the wrong ripple value? Thanks, I will investigate the B+ side of the flyback. This give me someplace to start.
OrdinaryCyborg
Posts: 9
Joined: Mon Sep 13, 2021 4:40 am

Re: Sony KV-20FV12 Jail Bars HELP

Post by OrdinaryCyborg »

So I've replaced every single electrolytic cap, double checked each one to ensure I didn't get any bad ones. All look good. I've replaced a handful of high voltage ceramic and film caps connected to the B+ side of the flyback. Still no change to the ripple.

I'm at a loss now. I've studied this damn KV-20FV12 schematic until my eyes bleed. I'm not sure where to look next. Maybe the voltage regulators? I have now invested way more into parts to fix this than what I originally paid for the TV and I very much overpaid for it. 

Is there anyone in the Portland OR area who is willing to take a crack at it? I'll happily pay. I am almost to the point of throwing this thing in storage and buying a new crt. 
Taiyaki
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Joined: Fri Apr 04, 2014 11:31 pm

Re: Sony KV-20FV12 Jail Bars HELP

Post by Taiyaki »

In my experience all CRT's have quirks and flaws, and unfortunately this is one of the innate issues with most of the later 20/24 inch Trinitrons (potentially larger sizes too). It shouldn't be noticeable in use but on solid color screens can sometimes be seen like in your screenshot.

If there is a solution to fixing it I've never seen it, and I've seen this on most consumer grade CRT's from like 2000ish and up from Sony. This doesn't mean one should go looking for older sets cause depending on the year and model they'll have their own quirks too. In my experience it's the same thing with other brands like Toshiba and Panasonic too, odd and unique issues on most lineups.

This is one of the two or so quirks of the FV/FS mid size Trinitrons (the other being the very high sensitivity to off NTSC standard frequencies).
OrdinaryCyborg
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Joined: Mon Sep 13, 2021 4:40 am

Re: Sony KV-20FV12 Jail Bars HELP

Post by OrdinaryCyborg »

Taiyaki wrote:In my experience all CRT's have quirks and flaws, and unfortunately this is one of the innate issues with most of the later 20/24 inch Trinitrons (potentially larger sizes too). It shouldn't be noticeable in use but on solid color screens can sometimes be seen like in your screenshot.

If there is a solution to fixing it I've never seen it, and I've seen this on most consumer grade CRT's from like 2000ish and up from Sony. This doesn't mean one should go looking for older sets cause depending on the year and model they'll have their own quirks too. In my experience it's the same thing with other brands like Toshiba and Panasonic too, odd and unique issues on most lineups.

This is one of the two or so quirks of the FV/FS mid size Trinitrons (the other being the very high sensitivity to off NTSC standard frequencies).
Thank you for this. As I mentioned in my first post, theres a ton of noise in the audio on this TV so this all feels like theres high voltage leaking into ground somewhere but I don't have a second perfect working trinitron to compare to. I've seen no bad or questionable traces or components anywhere on the board. If I get lucky on this thing, I'll post an update.
that1crzywhtguy
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Joined: Fri Oct 21, 2016 5:14 am

Re: Sony KV-20FV12 Jail Bars HELP

Post by that1crzywhtguy »

Any chance you returned to this or solved it? I have the same problem with a 20FS12.
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