No Green on WG25

[DaemonCollector]

Just got a cab and upon firing it up I found that on the color test screen there is nothing in the green, yet when I mess with the pots I can get the entire screen to tint green...but cannot get a green bar to show on the test screen. Anyone think its fixable?

[Ken Layton]

What model is the monitor? Wells makes 100's of different models each with their own quirks/problems.

What is the manufacturer and tube number of the picture tube?

[DaemonCollector]

its a Wells 25k7191 with a Zenith tube, i think the model is a E1A 1101. Thanks for any help in advance.

[Ken Layton]

The Zenith tube is known to go bad. Wells had major problems with Zenith and switched tube manufacturers.

I must have had 4 or 5 of these tubes go bad over the past 2 years. Rejuvenating sometimes helps, but I've had to replace a couple of tubes. I bought new replacements straight from Wells and got a good price.

However, you could have a bad driver transistor on the neckboard for the green color. I've also seen the trimpots go bad on the neckboard.

[DaemonCollector]

Hmm, so which do you think would be the first place to look? As I said I can get a green tint by adjusting the green trim pot and the cut off, so the driver transistor? In that case where would it be, I'm new the whole monitor thing.

[Ken Layton]

On the neckboard, transistor Q202 is the green driver. Working backwards from there the green signal goes to pin 19 of chip IC1 (UPC1397C) on the main board. Pin 4 of that chip is the green input fed from capacitor C5 (10 uf @ 25 volt BI-POLAR). Then to Q2.

[DaemonCollector]

Is there an easy way to check if its bad? I remember reading somewhre about using a jumper wire and tapping it to the case and if it flashes green that means its fine...is that not safe? is there a better way?

[DaemonCollector]

I FIXED IT Was the stupidest thing and I should have checked it first. The green signal wire from the game board was cut in half, reconnected it and the monitor looks like new.

Thanks for your help

[Grauwulf]

If only all problems were so easy to fix, eh? The easy things to fix are sometimes the easiest to overlook.