Tron voltage drop issue

Vectordreams

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I have two Tron machines and one is having issues with the 5 volt dropping to 3.3 when the video cable is plugged in and will not boot. I have rebuilt both suit cases, 90412 boards and everything works in just one cabinet. The oil cap looks to be new on the bad cabinet. Both are running 4900 monitors so I swapped chasis and it smoked a trace on the back of the board from the working game. Looking at the original chasis this has happened before as someone soldered that location of the trace.

I have tested with both cabinets side by side and plugged the monitor in from the working and did not drop voltage. Could this be a bad isolation transformer?
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Man you all over the place here brother....lol

One thing at a time.

Do you have a TPG that you can verify your monitor is in good working order? Sounds like a recap / rebuild is in order at the very least. Or buy a rebuilt one here on KLOV.

You said you rebuilt both the power brick and the 90412 lin PS. Did you test these and under and load?

What's @jacklick you tube videos on both. He walks you through how to test them. Once you've established the power is good it's into your harness and then the PCB. I always say just send the PCB stack to @cdjump as he's awesome at fixing these. But I'd do the steps above first before guessing it's a PCB problem.
 
This one has been been frustrating and I have been testing everything every which way. I replaced the pins on the wire harness for the 5 and 12 volts. Had a problem with my working cabinet that the pins had acid damage and would not always make a good connection. I figured it would not hurt to change them out.

Yes already rebuilt both monitors and I have tested with a TPG and only issue was no green color in the cabinet that has the voltage drop. This was why I was swapping chassis to see if the green transistor was bad or a tube issue. That is when it fried the trace. It was working perfect in the working cabinet.

Yes for both 90412 are holding voltages in my working cabinet and both MCR boards work.
 
Soldered the trace back with a jump wire and only issue I saw was the brightness was higher in the working cabinet.

Hooked back up the original chassis in the voltage drop cabinet with my bench isolation transformer and it still is dropping the voltage when the MCR is plugged in. Tested again with my TPG and no issues other than no green.

Since the oil capacitor looks like it was replaced can the wires be reversed and how would I test? I checked the wires to the suit case and everything matches the working cabinet.
 
Soldered the trace back with a jump wire and only issue I saw was the brightness was higher in the working cabinet.

Hooked back up the original chassis in the voltage drop cabinet with my bench isolation transformer and it still is dropping the voltage when the MCR is plugged in. Tested again with my TPG and no issues other than no green.

Since the oil capacitor looks like it was replaced can the wires be reversed and how would I test? I checked the wires to the suit case and everything matches the working cabinet.
That oil filled capacitor can't be installed backwards, it's across an AC winding. This thread has more info on what it does:

It it the correct capacitance? If you remove the output connector from the filter supply (suitcase) into the 90412 PS board, and measure the voltages, do you get the correct 8V (pins 4&8) and 15V (pin 6)?
 
I tested across pins 1 and 3 coming off the transformer and without the video plugged in I got 19.7 volts. Once the video was plugged in it dropped to 15.3.

I pulled the suit case from the working cabinet and plugged it in and now I have a stable 19.7. After swapping everything else the problem is the suit case. The caps were replaced before I bought the game and now time to test them.

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Having a very similar situation. Will have to look at the suitcase. Thanks for posting the solution for you.
 
Check the semiconductors in the suitcase, not just the caps. The semis do the heavy lifting. They do wear out and fail/degrade.
 
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