Hello - Pinbot blew the solenoid power fuse between between the transformer and bridge rectifier (my thanks to the person who added the fuses!!). Blew a second one immediately, so I figured a bad bridge. To make a long story short, I found that one of the ac legs is tied to ground, for both the 26 and 13.5 volt supplies. That’s with everything disconnected to rule out the rectifiers, etc; it’s coming out of 6P1 that way. According to schematic that’s not right. Just wondering if this is correct, a common mod for some reason, or maybe my transformer’s gone bad, and if I need to chase this as an issue.

Thanks. I finally got back to this today. I'm pretty confused about the secondary voltages related to ground. They're all over the place. However, all the voltages measured for all the secondaries (without regard to ground) are pretty good.

However, once I connect the bridge up with its negative output to ground again, the AC input voltage to the bridge shoots up from the normal ~26 VAC to ~41 VAC. Then the fuse blows again. (By the way, the original bridge tests fine out of circuit. I'm guessing that the high AC voltage leads to the fuse blowing. Hopefully that's all that's blown from there up, and more in the power supply isn't fried.)

I'm pretty stumped, and any ideas for further troubleshooting would be much appreciated. I hate to spring for a new transformer as my next troubleshooting step!

Pinbot Transformer Schematic 2 (resized).jpg

Thanks. I’ve got a lot to learn about the AC side!

So I tested the primaries and all the secondaries and found no (DC) connection between any of them or to the frame, and the secondary voltages are correct (ignoring the weird references to ground that I don’t understand). The transformer is fine.

I worked my way slowly from the transformer, through new bridge rectifiers and cleaned-up connections, to the power supply board. With the solenoid power output connectors from the PS board disconnected, I have about 35 VDC with no load and no fuse-blowing.

However, once I plug the solenoid connector into 3J3, the voltage drops to 25 VDC. (No fuse blew yet though.)

I’m guessing that there shouldn’t be such a voltage drop with the machine just sitting in attract mode, so I’m going to continue working down from there. OR... Does that voltage drop sound right? Should it be about 25 VDC going to the solenoids, or something closer to 34 VDC? The schematic doesn’t mention voltage under load (and I don’t know if there should be a load or what it might be), just that it should be about 34.5 VDC unloaded.

Thanks for any help!

After lots of searching and reading, I’m 90% convinced that ~25 VDC is correct for the solenoids. Everything seems OK now. This has been a great learning experience; even the wild goose chases regarding the AC voltages and chasing down the solenoid voltages were educational. I’m still not sure what the original problem was as the old bridge tested ok on the bench, but hey, it’s working now with new bridges so that’s what I’m assuming was the root cause.