Pac power supply issues

JonRomo

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Donor 2016
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Alright, so I went to fire up the trade and true Ms Pac tonight, and nothing happened. I went to check some voltages, and at the power supply, in not getting anything off of the transformers over 1v. I do have 2 blown fuses, but I imagined those arent making it output basically nothing. Any thoughts? (In the process of replacing the fuses now)
 
Alright, so I went to fire up the trade and true Ms Pac tonight, and nothing happened. I went to check some voltages, and at the power supply, in not getting anything off of the transformers over 1v. I do have 2 blown fuses, but I imagined those arent making it output basically nothing. Any thoughts? (In the process of replacing the fuses now)

Neither of the transformer read anything going out? Did you measure anything going into them? The fuses are definitely an issue too
 
Yes. Both have 120 going in.

Assuming you're measuring them correctly, which I'm sure you are, I would say that both transformers are bad, which seems unlikely. If I was you, I would wait to see what happens when the fuses are known good.
 
Alright. Now good fuses are all in place. And nothing has changed. Could this be because the board is not in, it may not be drawing the voltage it needs?
 
Alright. Now good fuses are all in place. And nothing has changed. Could this be because the board is not in, it may not be drawing the voltage it needs?

Did any fuses blow again?

Even if the board wasn't in, the monitor should still be powering up if the transformers are getting it power
 
Alright. So I put the board in, getting this. But, after looking at some test points, it's getting +5v. But at the chips im getting 4.4-4.5. IMG_0114.JPG
 
Attempt #2. I threw a different pac board in here(known working) and I get the same garbage on the screen. Therefore, it has to be power related? Correct?
 
Picture for documentation
#2
8a47a632cf7ea5bc11612bd5e15a552d.jpg
 
Well. After doing some research, I have realized that I know nothing about the power supplies on this thing. So after measuring everything how it should, I now have 12vac coming off of the bigger transformer block. This, from my understanding, should be 12vac. Is there any way I could jump this up, or tone it down if need be?
 
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are you measuring the DC voltage on the game pcb and getting 4.4vdc?? the input voltage is AC but the pacman pcb rectifies/converts the AC to DC via the two large resistors by the edge connector which are D7 and D8. check them and see what you have at those two diodes.
 
Alright, so after checking D7 & 8. Both are doing they're job, but the problem is the 12v going is is about 12.5, and on the other side, it's coming out as 15vDC
 
I would worry more about the +5v only being low at the chips. I rarely worry about the 12v. Something is dragging down the voltages that drive the logic.
 
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