CRT uneven brightness

[vol.2]

I have an older set (KV-9200) that I'm working on, and I've noticed that the right side of the screen is just a touch brighter than the rest of the raster. It's only noticeable at lower brightness levels, but it's easily apparent.

I've already gone through and replaced any caps that were out of spec (was pretty much all of the electrolytics), and done a setup on it. The only thing I didn't do was color purity, but that seems to be okay performing the typical raster test, and it's not the typical color purity issue you see with splotches, it's more of a uniform rectangular area that's about 1/5 of the screen on the right

I've been doing a lot of research for these symptoms, and I've come across a bunch of people saying that both Well Gardner CRTs and also 70s Japanese sets will have a bad cap on the neck board (typically in Wells Gardners on the 200V rail on the neck) that needs to be replaced to fix this, and a lot of people over the years have recommended upping the capacitance of this cap to completely eliminate the issue.

I'm trying to identify if this might be a fix for me, and I'm looking at altering the capacitance of this one .47uf electrolytic on the 300V grid. Any techs here know enough to know if this might be a good fix, and how much I might try going up to alleviate the issue?

[matt]

That's a common problem. It's caused by a filter caps on the bias voltage for the RGB amps, which often fail due to constant ripple current. Those are sometimes on the neck board but not always. Sony TVs of this age usually will need a bunch of new caps - the ones they used aren't very good.

On your TV, the most likely culprit is C524 (47 uF, 50 V) which should be located near the flyback. By extension, C522 (33 uF 160 V) is the B+ filter cap and could also be on the way out. C704 appears to be the filter for the G2 voltage, which could potentially cause the same problem and should be changed anyways.

You could try upping the capacitance, but if you replace with the same values the TV should be fine indefinitely. Unlike an arcade monitor you're not going to run it 24/7.

[vol.2]

That's a common problem. It's caused by a filter caps on the bias voltage for the RGB amps, which often fail due to constant ripple current. Those are sometimes on the neck board but not always. Sony TVs of this age usually will need a bunch of new caps - the ones they used aren't very good.

On your TV, the most likely culprit is C524 (47 uF, 50 V) which should be located near the flyback. By extension, C522 (33 uF 160 V) is the B+ filter cap and could also be on the way out. C704 appears to be the filter for the G2 voltage, which could potentially cause the same problem and should be changed anyways.

You could try upping the capacitance, but if you replace with the same values the TV should be fine indefinitely. Unlike an arcade monitor you're not going to run it 24/7.

Thanks Matt,

So I just checked my notes and I replaced 100% of the electrolytics because everything I tested was dead or way out. I only use high quality Nichicon and Panasonic for things.

So maybe it's one of the film caps? I didn't test all of them there's so many. I have the Sam's for this, so if you've got any ideas and you want to see a schematic I've got it and can do screen caps

I could just start testing stuff, but yeah it's a huge job to run through all of the films without any direction

Or possibly like I was saying originally, I should try upping the uf of one of the caps like they suggest on the Wells Gardners?

Also, just looking back at my work here, I now realized that I replaced C704 with a film cap because it's a 0.47uf 500V cap and I only had film caps at that rating on hand. I wonder if that could in and of itself be causing the issue? I'll have to buy an electrolytic replacement to be sure of course though. I also just checked Mouser Electronics and it doesn't seem I can even buy an electrolytic 0.47uf at 500V anymore. The best I can do is 450V, which idk maybe that's fine here because the G2 is like 300V, so I don't think it will ever see 500V? I guess if there was a spike, but I don't know if that could happen here.