WG79xx - screen is blue

cueball

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Donor 2011
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wanted to see what the opinions were on what is wrong with the wg79xx. i recapped the chassis a couple of years ago and recently the monitor went blue. it was in a dual cab cyberball (that was converted to a run&gun). i took my TMNT board to eliminate the pcb as the potential issue.

with the tmnt board, you could see shadows of the Federal Drug warning and such, but clearly it is blue all over and unplayable.

Before I swap out with other chassis to see if it is pcb vs a tube issue, what is wrong with this? nothing obvious is notable on the flyback or any chassis components.

i am also placing a parts order later today so i want to include the necessary parts to repair.


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Unplug the connector near the flyback that goes up to the neckboard. See if the blue goes away. If so, then look at your IC on the main chassis. if not, then remove the blue transistor on the neckboard to see if it goes away. if so, then replace that transistor. If not, then you may have a tube issue...
 
Unplug the connector near the flyback that goes up to the neckboard. See if the blue goes away. If so, then look at your IC on the main chassis. if not, then remove the blue transistor on the neckboard to see if it goes away. if so, then replace that transistor. If not, then you may have a tube issue...

Looks like it was a tube issue. I tried unplugging the connector and got nothing. The I realized that I had a 7900 monitor with a known good tube but waiting for vertical deflection repair. Swapped chassis to test and confirmed the tube is bad.

I had another spare 7900 That I didn't know the status of the tube or chassis. Turns out that the chassis is dead but the tube is good

I swapped that tube out and fired it up. After a little vertical hold adjustment, I am ready to reinstall for the customer..
 
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