White problem

[hsinn3r]

Hello people,

I recently got me an OK Baby arcade cabinet, with a Neo Geo arcade board.
I'm facing a problem with the display. Using the cabins test mode (it displays four small squares, one for each primary color and a white one), I can get the colors themselves to display properly, with no bleeding. But on a full white screen, for example on the Neo Geo logo screen, the display is dim, and the result is a gray-ish, instead of a bright white.
When displaying dark and colored items, it looks ok.
The brightness pot is on full, and the other pot that resides with the focus pot, is as high as it can go without displaying horizontal lines.

Should I recap? Or is the screen done for?
Also when recapping, should I change all the caps, including the small resin-dipped ones? Or just the typical electrolytic (black and white barrel)? Pics follow, thank you in advance!

Screen sticker:


Circuit board sticker:

[grantspain]

have you tried the colour gains and cut offs?

[hsinn3r]

have you tried the colour gains and cut offs?

Hi, thanks for your reply.
Yes, I've tried both the gains and the cut offs. If I tweak the gains on a white background, I can get it to be bright when cranking the pots, but then everything else looks... psychedelic
Bringing the brightness down only reveals huge amounts of color bleed.

So I'm thinking that the monitor itself is capable of being bright, but can't on the current control board.

I'll try to make a BOM for the capacitors and order replacements.

[grantspain]

no harm in trying caps,cheap and easy to do

[hsinn3r]

no harm in trying caps,cheap and easy to do

Will do. I'll update on the result (in about a week or two).

[hsinn3r]

Well, that took a while.

I replaced the whole chassis, and still no luck. I'm looking into rejuvenating the tube now, any thoughts?

[lilshawn]

Don't forget you are looking at a low resolution CRT tube picture, not a 1000000:1 contrast ratio plasma display. it's not going to be super duper sharp and retina burning bright. there is going to be variances in brightness and blooming of the picture.

that said, full screen brightness variances are usually caused by fluctuations in the main B+ high voltage. the capacitors filtering the B+ get weak and cant pump out the juice like they used to and become more of a load then a help. i'd start like others mentioned with a "cap kit" and change them. if they are original and haven't been messed with before, change them.

don't go messing with controls on the board, you can end up making things much much worse, especially if you've cranked up the B+ voltage to try and compensate for extra load of weak capacitors on the rail. When you change them and power back up... POOF! all kinds of destruction because that load is now gone.

[haynor666]

Typical problem of CRT displays, not just arcade monitors but also TVs. I have one TV with such problem and had another one with the same problem. Sadly I don't know what causing this (I assume it's caused but aging) so from time to time I search for another TV :/

[lilshawn]

If the tube is getting wore out,  you crank the gains on the colours and crank up the flyback and things just Gray out.  The emissions from the guns are usually to blame.  Sometimes a tube rejuvenation can restore it quite a bit,  but it's really hard on the tube. And can make the guns unbalanced to the point where you can't get good color reproduction.  Sometimes a rejuvenated tube will last year's... Sometimes months.  Sometimes even less.

But,  by the sounds of OP's description the tube emissions are okay,  the chassis is just having a hard time pushing voltage through the tube to get the electrons flowing when it's under high load (solid white)

[haynor666]

Hmm, even it's really typical problem so far we don't have a clear answer - fixable or not fixable. If fixable then how. I wonder if Ken Layton knows solution.