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Monitor colour issue


Jesder

Question

Hey guys,

 

Hoping to get some help with a colour issue I'm seeing with the monitor in one of my arcade machines.

 

I switched it on today to play Wonderboy for the first time in a couple of months and found the colours were not correct. Unsure if it was an issue with the game board or monitor related, I grabbed a different game board (one with a colour test screen) and found that the display was the issue.

 

Here I've got a 60-in-1 hooked up in one of my other machines. This displays the colours correctly - one thing to note is it's running a PC monitor and not an arcade monitor - but the colours appear here as I expect they should.

 

test_colours_good.jpg

 

Now I have the 60-in-1 board hooked up to the machine with colour issues. It displays red, green, blue and white on the test screen - but the colours are not in the same order as the previous image. Looking at the squares from the top left it's showing blue, green, white and red - which does not match the green, red, white and blue shown in the previous photo.

 

test_colours_bad.jpg

 

Now I see why the colours in Wonderboy do not look correct. The last time I had the machine on, the colours were fine. The chassis isn't very old - maybe 3 - 4 years. To me it's like the r, g and b have been swapped around, but no work has been done on the machine that would suddenly cause this. The only thing that has happened is the machine has been moved from inside the house to the garage - but it was done smoothly without it being roughly transported.

 

I've marked the current positions of each pot, but before I go adjusting, I'm hoping to get some input about possible cause and solution. Is it something as simple as adjusting the pots? Or is there something more sinister at play?

 

A couple of photos of the neck board and chassis in case that helps. There are 3 pots on the neck board, which are marked as R, G and B

 

 

monitor_1.jpg

 

The 3 pots on the left side of the board here are marked as R gain, G gain and B gain. The pots along the bottom of the board are for brightness, contrast, v hold, h pos, etc.

 

The white plug on the lower left runs to the JAMMA connector (R,G,B, ground, sync).

 

monitor_2.jpg

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Degauss the tube. Do you have a degaussing wand? If not, buy a cheapie one and it will likely sort your issues.

 

Moving cabinets causes all kinds of magnetic interference. Degaussing it sets it back to normal. A degaussing wand is just an electromagnet in a plastic wand, you press a button and wave it in circles around the tube and it fixes discolouration.

 

EDIT: If that doesn't fix your issues, then it's time to start looking deeper. But don't adjust any pots until you degauss. It's always the first step.

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Do you have a spare 'large' speaker speaker lying around? Run the speaker magnet around the screen and see if it pulls the colours back into place. Worth a try.

 

The cheap wands are :o

 

If you have a few arcade machines, get one of these. Had mine for 20+ years.

 

http://www.wagneronline.com.au/crt-degaussing-wand/test-measure/tools-test/6657/fl/

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