Bought an MPU327-3 In May and finally have it installed in my Firepower. Game and diagnostics worked fine for a few days but now the left kicker (solenoid 22) is locked on but only when a game is started after pressing the start button. When the machine powers on, the coil isn't energized at all. Only when a game is started. When running the solenoid test in diagnostics mode, the coil locks on as well. The driver for the kicker, Q12, tests fine. Dropped the folks at Rottendog a message too but was wondering if anyone here might have had a similar problem or suggest somewhere to start? Thanks!

Hey Zac! Nope... unplugging the actual special solenoids connector (2J12) does but not the special switch input connector.

BTW... still got the old boards for you. Let me know next time you're in town...

Sent you an email with scans of the schematics... the drivers run back into IC9 which looks like a buffer according to the part number?

Ok... making progress here I think. Here's what I found:

In game-over/attract mode - IC9 pin 4 and 16 are low
In-game - IC9 Pin 4 is low and 16 is high

Both during game-over/attract and in-game - IC7C pin 9 is reading nothing at all but pin 10 is reading high

In diagnostics mode - IC7C pin 9 again nothing and pin 10 alternated between high and low as solenoid fires

Thinking IC7 might be the culprit?

IC7 pin 9 is giving no reading at all with 2J13 unplugged, either in attract or in-game. Nada. Weird...

Tested resistance with test point VCC - On IC7, pin 9 is .09k and pin 12 is .02k. They're way off... aaaaand that might be because now the right kicker isn't working at all. I compared readings with the special solenoids for IC8 (pop bumpers) and all those test a solid 4.7k.

I'm tempted to test it but yeah, to your point I'll see if there's some warranty goodness involved. Or maybe even some additional info from RD. I thought I had a good hang of the original MPU/driver and then got hit with this which is a whole different animal... tons of thanks for the help though, dude. Gives me a better understanding of what makes these things tick.

Just spoke with Jim at RD this AM... dude is rock n roll all the way. Narrowed it down to exactly what we suspected and I swapped in a new 7408 at IC7 and we're back in business. Aside from me wanting to burn this game to the ground every time a problem comes up (I keep reminding myself these are 40+ year old toys and they need constant work) this has been fun figuring out the problems. Thanks for all your help zacaj and a big shout out to Jim at Rottendog for getting back to me so quickly and confirming the problem. I'm gonna go fry something else on the game while putting this hardtop in.

edit - I think I shorted a switch to a solenoid which fried IC7. Whoops!