Arcade Collecting > Pinball
High Voltage not high enough
Blanka:
It's quite normal that a unloaded transformer gives higher figures than a loaded one. 190V AC sounds Ok for an 173V unloaded trafo.
ChadTower:
Plus the transformers themselves almost never die. Those things are heavy duty.
Neverending Project:
OK, next thought. I checked all four diodes on the board and they all test good (and they are all new), and I didn't find any shorts either. Even though the voltage at the test point seems to be out, should I focus my troubleshooting on the SDU, since I can't imagine what else could be wrong with four simple diodes?
Or I could try to find a replacement power supply board to test it in place, so I can rule out the board as a problem. What would you guys do next?
ChadTower:
I'd probably bring the displays to a good machine and make sure they are still good.
Neverending Project:
--- Quote from: ChadTower on January 07, 2009, 10:39:48 am ---I'd probably bring the displays to a good machine and make sure they are still good.
--- End quote ---
Since none at all are working, and the trim pot does nothing to adjust the HV, and the test point is too low, I am going to try to get the HV fixed first. If I get the HV in range and they still don't display, I will see if I can figure out a way to test the displays (I don't have any good machines to test them on).
I have been pouring over these boards, trying to see if I installed any parts wrong or shorted anything. I cut out a 100K resistor on the SDU thinking it was bad (it didn't test in range on the multimeter), but it turns out it was across the filter cap, so the multimeter couldn't test it in circuit. So that wasn't the problem. I checked all the other resistors and they are fine.
So if there is a problem on the SDU, it would either be with the zener diode at the center tap of the trim pot VR1 (new), or maybe I shorted the one of the leads of Q21. I am going to replace the diode and resistor I clipped and see if that does anything.
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