Stern "Big Game" Transformer Problems

tyty7777777

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I have a client who has just bought a Big Game pinball machine by Stern from around 1980. The machine was working at one point at their house and now nothing powers on. First I replaced the rectifier board with a new reproduction one from Marco Specialties. The old one was definitely on its last limb. Hoping that that would solve the problem, I turned it on but nothing happened once again. I traced the power from the 120v in and got a reading all the way into the transformer, but then the voltage stops there. The transformer seems to not be outputting any voltage to the machine. I find this odd; everyone says that the chances of have a problem with a transformer is less than 1%. Attached is a schematic for the transformer.

Thanks
 

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I would pull the fuses on all the secondary winding circuits, power up the primary, and read each secondary AT the transformer.
Edit: Ohm each fuse while you have them out and make sure you put them back in the correct location.

Did you have the 115V at the transformer taps? Never mind, just reread your post that said you did.

Where are you located?
Edit: I have a transformer from a Stern Flight 2000 that you can have (free) if needed, if you can pick up. Sorry, will not ship.
 
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I would pull the fuses on all the secondary winding circuits, power up the primary, and read each secondary AT the transformer.
Edit: Ohm each fuse while you have them out and make sure you put them back in the correct location.

Did you have the 115V at the transformer taps? Never mind, just reread your post that said you did.

Where are you located?
Edit: I have a transformer from a Stern Flight 2000 that you can have (free) if needed, if you can pick up. Sorry, will not ship.

I'm not exactly sure how to test the voltage at the transformer. Which will be + and which will be - ?

Thanks
We're in Sheboygan, WI btw so I'll keep that in mind if she really needs it.
 
I'm not exactly sure how to test the voltage at the transformer. Which will be + and which will be - ?

Thanks
We're in Sheboygan, WI btw so I'll keep that in mind if she really needs it.

I would first check F6 as Dokert suggested if it's good then set your meter to AC volts and verify the voltage of each secondary winding as indicated in the schematic. Everything on a transformer is AC it only changes to DC after the bridge rectifiers.
 
Power down, pull each fuse, and ohm them, make sure to put back in proper location.

"everyone says that the chances of have a problem with a transformer is less than 1%" - they are correct.

Your first post said you, "traced the power from the 120v in and got a reading all the way into the transformer".

If you didn't realize that all the transformer voltages were AC, then you may not have read it correctly. Ohming the fuses out of their holders would be the most reliable way for you to check them.

To check the fuses with power on, you should be on the Voltage AC scales. Put either lead on one side of the fuse and the other lead on the other side of the same fuse. 0 VAC is a GOOD fuse. BAD fuse readings would be ~120VAC on F6, ~7.8VAC on F1, ~173AC on F2, ~12vac on F3, ~43VAC on F4, and ~7.3VAC on F5.
 
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So. I feel stupid. The reason that the transformer wasn't putting out anything was because the molex connector going to it was not making proper connection. I had it in tight, but that was apparently not enough.
There is now a new problem. The F3 fuse (+5 logic) blows when the test or memory clear buttons are pressed. Also, after a few minutes of play the fuse went out again.

Thanks once again.
 
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