DOT Power Supply Issue - Resolved

davefinn

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Donor 3 years: 2015, 2020, 2024
Joined
Dec 17, 2011
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Location
Sicklerville, New Jersey
I had decided to get the original linear supply working in my DOT and remove the switcher & power adapter that someone had installed in the game before I picked it up.

I recapped, installed a button cell battery and tested the linear supply with the transformer assembly & P/S sitting outside the game. I adjusted the 12 volt supply & 5 volt supply under load and all was looking good on the meter.

I then had issues with the 5 volt fuses blowing on the transformer assembly when everything was reconnected inside the cabinet.

Long story short, I found that one of the 12 amp stud mount diodes (see picture) under the transformer assembly had shorted and was applying about 8 VDC to the metal chassis of the transformer assembly. This was causing the issue because there is a ground strap connecting the transformer assembly metal case to the audio amplifier board. The fuses would not blow if that ground strap was removed.

I found a few diodes on Ebay and have replaced the shorted one. The game is now 100% functional and running on the linear supply.
 

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Nice troubleshooting, and good job getting that switcher out of there. Long live the MCR linear!
 
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