K7000 Brightness not holding

[Neo_MVS]

So here is a problem that my NEO GEO Gold Cab is having that is driving me up the wall. A few weeks ago, I turned the cab on and the picture was very dim. Prior to this I had replaced all the caps on the monitor board and the picture was very good (it worked fine for about 6 months). So, I opened the back of the cab and turned up the brightness pot, and the picture went back to normal. I played that way for about 20 minutes, when all of a sudden the brightness jumped back up; the screen washed out and I had to turn it back down. When I would turn the cab off, leave it for awhile and turn it back on, the brightness would be low again, and the cycle would repeat.

Step one, I tried to clean the pot. It did not help the issue. while I was cleaning I did notice that the pot felt a little too loose. So, I had a friend solder a spare I had. Now things worked fine. No more brightness variation and I sealed the cab back up.

A few weeks later; and the monitor is doing the exact same thing. You turn on the cab and the brightness is very dim, you can turn up the brightness and play for 20-30 minutes until the brightness jumps and the screen washes out.

Any ideas what might be going on here? Thanks for any help/advice...

[Ken Layton]

Possibly the "SCREEN" control inside the flyback is going bad, especially if this monitor still has an original flyback.

Another possibility is the picture tube is developing an internal short which can be tested for and might be repaired using a rejuvenator.

[Neo_MVS]

Ken,

Thanks for the reply. I am not sure about the condition of the flyback, I bought the chassis from a member on ebay when the original suffered a vertical collapse. At that time, he stated that the board has been re-capped and that all components tested good.  Is there a way to clean this "screen" control I can try? Where is it located?

As far as a tube short, I have not noticed anything strange...no arcing or strange sounds from the monitor. Any signs I can look for? Where can I find a rejuvinator? Anyone in SE WI that works on monitors that wants to come help a newbie out and play some NEO GEO? 

[FrizzleFried]

I have a K7000 doing almost the same thing.  When I turn it on,  it's dim,  but after about a minute of warm-up the screen will instantly pop on to the correct brightness.   I've had the same happen with the brightness dropping back down mid-gameplay but it happens much less often.  I also notice that when the brightness drops,  the blue color gets washed out and all the whites turn "dirty" white.   This tube is one I rejuved recently...prior to rejuving it would do the same thing go,  but it went from looking pretty bad with washed out colors, etc to looking TERRIBLE with real real dim colors at that time... so the "brightness" jumping was evident prior to and post rejuv...

[Neo_MVS]

Glad to hear I'm not alone, misery loves company. Arcade ownership is proving to be much like my classic car. It's a money pit, and something is always just wrong enough to really bug you.