I've been working on a Hot Hand. I bought a handful of components to replace on the solenoid driver. A couple resistors and diodes were bad. The header pins looked fine so I reflowed them. I will probably replace them just in case. CR21 and R35 both give me odd readings in circuit even though I replaced them. With the board installed I can get the displays to turn on by finding a sweet spot on the potentiometer. This sweet spot is letting the full 240v to the display. The pot seems to test fine other than a few odd spots in the sweep. This doesn't make sense to me, hopefully replacing it solves my problem. I have a few questions.

Could a bad pot be causing me to get weird readings on the diode and resistor?
Are there any other parts I should consider adding to my order in addition to the pot?
How long can I run the displays with full voltage before I damage them? I was hoping I could run it for a few minutes at a time to troubleshoot some other stuff.

I also did the 2 capacitor ground mods and the TP 1-3 mod.

I should have added I did replace those 2 caps. Not sure what you mean by 5v regulator and 190v. I'll do some more research.

The 3 transistors tested fine in circuit. I will try them out of circuit. Might as well add them to the next order either way.

I was considering this. The pot is 25k. I must have something in the 12k range lying around just to test it.

I would put the resistor on the center lead and whatever lead had resistance. Would I need anything in the 3rd hole? I'll have to see if I can make some sense of the schematic.

edit: Looks like I need all 3 legs of the pot, so I assume that means I would need 2 resistors? I wish I understood schematics a little better.

I just ordered 3 transistors and the pot. That means I'll have just about every part on hand. Hopefully one of those will fix me.

I replaced the 3 transistors (I think they were fine) and the diode at VR1 (almost sure this was my culprit). I can adjust to 170v and all my displays light up. I wish I understood a little more about the schematic. I'd like to know why VR1 was causing R51 to heat up 2 6,000 degrees and make a perfect resistor sized burn on the tip of my index finger. Now to figure out why the big flipper stopped working.....

Thanks for the input!

Rotating flipper issue turned out to be a disconnect I missed. Every once in awhile it's something easy! I think this game will be ready for Pintastic! Now to get working on the other 2 games I promised to bring......

Thank you. I do understand what a diode does, I just wish I could follow the chart a little better. I replaced VR1 because it was the last thing I might not have replaced. I don't want to always take the shotgun approach. I wasn't getting anything at the potentiometer. I guess I could work backwards and the next thing is the VR1 diode. I'll get it one of these days...