Working Monitor chassis tics, then starts buzz, so I turn it off and now bad fuse...

Teknotoyz

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Working Monitor chassis tics, then starts buzz, so I turn it off and now bad fuse...

OK, bought a 2-slot Neo Geo that has this QNIC monitor in it, model CGM-2500.
The monitor worked, good picture although a little stretched at the top.

Started making a ticking (static) sound, then a mid level whine from the chassis....
I turned it off and then back on and now the fuse has blown.
Picture was stable the whole time the noises started too.... puzzling...

SOooo, I need some help with the monitor in terms of suggestions,
1.) I'm gonna run get fuses tomorrow to retry (good/bad idea?)
2.) I plan to order a cap kit from Bob Roberts....
3.) Need to check HOT and flyback..... how to check HOT on this?

ANY help would be appreciated!!!
Very little out there on the QNIC... no big lovers or haters..
 
WOW, no love for QNIC??

Anyway, poking around on it revealed why the fuse blew.
Two of the rectifier diodes are shorted.....

I'm wondering if the buzzing was the AC leaking through... who knows....
Can I hope that it's only 2 diodes....
Checked and the HOT isn't shorted (Red probe on center, checked either leg).
Flyback looks OK, no cracks or anything I can see.
I would have thought that if it were the flyback, the ticking would have had been with picture collapse.
 
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i know nothing about that monitor chassis BTW.

is there an iso in the cab.

or does the monitor chassis have one built in.

Peace
Buffett
 
i know nothing about that monitor chassis BTW.

is there an iso in the cab.

or does the monitor chassis have one built in.

Peace
Buffett

I think your in the majority, I'd never heard of it before either.
From what I can figure, these appear to be common in Neo Geo's.
Bob Roberts sells cap kits and HOT's for it.
Just sent the manual to Basement Arcade, Arcadecup, and Mike's arcade so they can add it to their archives.

There is indeed an isolation transformer in the cab (not on chassis).
I metered it to ground just to double check and it looks fine.
 
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Check your retrace cap. Its the one connected to both the hot and the flyback. Its possible that its shorting out. It also could be the voltage regulator is shorting to the heat sink or something similar.
 
Woot Woot!
Got it all figured out!

I replaced the diodes (all 4, only 1 bad) and fired it up.
The picture came on, looks good, but the damn buzzing was there.
Looked close into the back and could just barely make out a blue plasma stream at the flyback.
Never seen this before on any monitor. Really glad I didn't try to adjust the flyback!! :D

Powered down quickly, and upon close inspection, there are hairline cracks in the flyback housing.

So the ticking was the flyback starting to arc off to the heat sink metal around it.
It got worse and the buzzing is a continuous "leak" from the flyback.
The blown fuse was a single shorted rectifier diode.

I did manage to snap some pictures, will post later.
 
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