Lacking red on monitor, 17 inch Game King 3902.

[Bmwsyc]

New to me machine, also new to Game Kings. Initially not working, found shorted wires between the isolation transformer and the monitor chassis, and a blown fuse in the isolation transformer. Everything is working now, but the screen is lacking or doesn’t have any red at all. Are there adjustment pots for color? I checked the connections from the monitor board to the 19 pin connector and took a brass brush to the pins.

Is there a trick I don’t know of, I couldn’t find any pots for color. Is it time for a new monitor or re caping?

Thanks!

[Tilt]

It would be helpful to know the make and model number of your monitor.  Many monitors have RGB driver and cutoff adjustment pots on the yoke board on the rear of the crt.  See if yours does.

[shortrackskater]

Moved to CRT and LCD repair
~moderator

[Bmwsyc]

Ceronix 1793, I looked again, I didn’t see anything obvious.

[Tilt]

You're a contributing member so you have access to the downloads.  There's some 1793 documentation that you can download that may be helpful.

https://newlifegames.com/nlg/index.php?action=downloads;cat=18

[Chris-socal]

The 1793 appears to use similar electronics as the smaller 1492. Brightness and bias are electronically controlled, you won’t find individual color pots like other monitors. The gain pot on the remote board sets a baseline, an IC maintains that level as the tube ages. Its great…until it isn’t.

A single color going out could be one of the transistors in the color section of the board. Look at the 1793 manual, page 69. There is a schematic for the blue circuit, Red and Green are the same circuit design, one below the other on the circuit board. Use a diode tester to check the transistors in the red circuit, chances are one is shorted or open.

Secondly it could be a diode on the neck board, they should be labeled rgb. Easy to check those. It could also be one of the resistors burnt out.
More rare, it could be the red color gun is really weak and needs to be rejuvenated. But you usually some color.

It is important to do a close up visual inspection of the traces on the board. A cold solder joint on a transistor or on a ribbon cable could drop a color signal.

You can also send the board to one of a contributing shop. I know KLar services Ceronix monitors. But if the only issue is ine color missing it should be findable.

Good luck.

Chris

[Bmwsyc]

Thanks, Chris. That was my impression when I read through the manual. Automatic control. I’ll take a look at those two spots and see. I’ll also check for bent pins off of the main board.

[Chris-socal]

I looked at a pic of this board. Looks like color circuits are on the neck board. I highly suspect a transistor on in the red circuit. If you diode check them you will usually be able to find two of the 3 pins shorted using diode checker on multimeter.
There is a used board on eBay right now.

Chris

[Bmwsyc]

Thanks for your help, I have some direction now. I”lol check it out when I get home.

Thanks!

[Bmwsyc]

Just an update, the red amplifier did look like it had been replaced at some point, the solder job looked different and the flux was not completely cleaned off. I cleaned up the socket pcb and the main monitor pcb and reassembled, no change. A transistor started arcing on the main pcb so I just ordered a set of boards off of eBay.

The monitor is working now, all colors are there, but everything is backwards and up side down. I have an idea what’s up, I’m going to check that later. The horz and vert deflection coil plug didn’t fit on the new board because the pins were different, so I modded the plug. I’m guessing I got the horz and vert flip flopped.