Tech: Bally AS2518-54 Power Supply / Transformer Issues

EagleTG

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Tech: Bally AS2518-54 Power Supply / Transformer Issues

I'm working on a Bally Mr. and Mrs. Pac-Man that is getting very similar readings from both TP3 and TP5 on the Rectifier board. TP3 is 44v (should be 11-16v) and TP5 is 45v. The readings are not the same between the two test points, but are very close.

This testing is being done with J2 and J4 connected, J1 and J3 removed as-per PinRepair.com.

I've swapped in a known-good rectifier board, and am getting similar results. At this point, I'm suspecting the transformer.

This transformer is slightly different than other Bally games I've seen, as it has a 120v output (assuming isolated?) for the fluorescent bulb in the backbox. Is this the only difference?

Does anyone have any further input that might help me troubleshoot? Everything I've read (and all prior experience fixing pinball) has told me that voltages are usually low or missing... This voltage being too high has me a bit lost.

Thanks!
 
As a quick follow-up, I've found this thread which seems to explain exactly what I'm seeing.

http://www.gamehourz.com/Stern-Power-Supply-Rectifier-Board-Voltage-Issue-ftopict148902.html

Following Ray's suggestion, I have tried a different multimeter and see that I am getting 36v on the TP3 instead of the 44v shown with my other meter. Unfortunately I don't have an analog meter to try (as referenced in the thread).

I am wondering if these are just odd-ball readings due to some ground reference (like mentioned in that thread)... Should I plug it all together and see if it works, or am I risking damage?

Thanks again!
 
One more follow-up to my own post... Sorry.

I grew a pair and based on the thread I linked above moved to the next step in testing voltages (Remove Connectors J1,J2,J5 and HV Fuse from the Solenoid Driver Board and Remove Connector J4 on the MPU Board)... Voltage tests are solid, I've got an MPU boot issue, but that's progress!

The TP3 voltage becomes +5v regulated, which I'm reading at 5.1v... So that's good.

If anyone has any comments or suggestions, please feel free to share. It's bizarre to get these readings on TP3.
 
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