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Arcade monitor has intermittent Blue

Although I'm no expert, I'm trying to repair the monitor inside an arcade cabinet. It's a Selti 22.0244.2. The problem is a low blue on the screen, that from time to time will flash "good" just for a split second. I suspected a dirty potentiometer and fiddled around with the

3 pots on the main board, but the problem didn't change. I also tried disconnecting and reconnecting the plug that carries the video signal from the arcade board with no effect. The electronics are exactly the same as those shown in this page:
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named selti#.jpg. There are three more trimmers (although different) on the small board that is attached to the tube but I haven't touched them yet. The thing was built in 1992, so I'm thinking of replacing the electrolytic capacitors, too. Any help is much appreciated.
Reply to
barabbadruso
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Swap the blue drive with one of the other guns to see if it's the CRT, or the electronics.

--
You can't have a sense of humor, if you have no sense.
Reply to
Michael A. Terrell

If you are able and comfortable with working around 200 volts or so, check the voltages around the video driver transistors on the CRT neck pcb. Possibly the transistos associated with "blue" has an issue.

(opening emitter-base, etc) This assumes a crt-based monitor, of course.

Mark Z.

Reply to
Mark Zacharias

There's something strange on the RGB board!

There are 3 sets each consisting of:

2 BF871 transistors 1 390 Ohm 2W resistor 1 trimmer

But! The 3rd one, where the blue wire goes, has BF869 transistors and a strange resistor without coloured bands. The trimmer is adjusted all the way to one end, unlike the other two. On the solder side, I can clearly see the brown remains of a rework (burned flux, I think) under the resistor and the 2 transistors.

Reply to
barabbadruso

So, copy one of the good channels and undo the sloppy work. for a quick test, swap the green and blue input wire, to see whether the board has an error, or the fault is in a previous circuit.

Reply to
Sjouke Burry

Does sound like you are in the right area...

mz

Reply to
Mark Zacharias

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