Wells Gardner K490x monitor "collapsed"

twobad

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I have a WG K490x chassis that I did a cap kit on last month. Picture was greatly improved. My son was playing and the screen "collapsed" to the center (see pics). A nice guy at the arcade controls forum suggested it might by transistors Q302 or 303. Both are intact (no broken legs). While inspecting them I found I had a cold /bad solder joint on C313, I reflowed it and was up and running again. After an hours solid play a hard push on the joystick caused the screen to collapse again. I suspect it's another cold solder joint as nudging the machine causes the picture to "fill out" and then collapse again immediately.

Is there a way to measure the C B and E legs of the transistors with the chassis removed/depowered to see if they are good?

If so, what should the measurements be?

From the attached pictures, can anyone tell which component might be the culprit?

I don't mind reflowing all the joints but I also dont want to stress- mess up a trace on the PCB... the relatives are in town for the holiday and everybody wants to play MsPac.

Sincere thanks,
-=T=-
 

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If you are using a good soldering iron, you can re-flow without stressing the traces.

You have found your smoking gun - re-flow the entire transistor this time to resolve the issue.

If you don't have a good soldering iron, I'd suggest you get one asap. Frys sells the Hakko FX-888 for around $80. Trust me, you'll thank me after you buy it. It heats up fast, and makes quick work of re-flows.

How quick? 30 connections in around 14 minutes, including using my Hakko FX-808 to de-solder some, and then re-solder with the FX-888.
 
I use a Weller WLC100. I think the counter guy at my local electronics store was getting his jollies convincing me to buy it but I after years of other work and then recently recapping two monitors I thought it was doing an OK job. The component I reflowed lats time was a capacitor. You are suggesting I reflow the transistors?

Thank you again,
-=T=-
 
I reflowed the two transistors and several of the caps in the vicinity that I previously replaced.
Ms Pac eats again!

THANK YOU AGAIN,
-=T=-
 

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