I am at a loss with this Mpu board, this is my spare board which I work on from time to time.
Here is my problems:
Booking is not being saved, when I go through the tests it don’t show the quarters in shoot 1 nor shoot 2
I’ll set replay at 210,000 280,000 and 350,000 and high score at 400,000
When I run through the test 7-10 it saves 10,001 for 1st replay 0 for 2nd replay 10,001 for 3rdand 10,001 for high score.
Another odditiy is when I shut it off and turn it back on the credits show 33 and match 70 which isn’t bad but it will only accept 1 credit more no matter how many quarters I put in. The chimes work as though I’m adding credits but only 1 credit is added. Here is the chips I had changed out thus far:
Z22, Z5 Z2 C22 C27 Q5 and Q6
I should note I have a battery pack (3 AA) with diode on positive with band towards the board.
Please any advice (besides tossing out the board) will be appreciated

Yes this is a original board the acid damage was minimal I cleaned and neutralized the area the best I could.

I’ll check the voltage on the Z22 it should be getting 5 volts correct? Which legs should I be checking?

Sorry to sound so ignorant, but I’m learning as I go. I would think that you should test the ram with the power on. With that said, would you use the comman ground? Should each leg have voltage? I would think at least 1 of the 22 legs would be ground. How do you test the chips?

When I checked the ram for voltage I got 3 volts on pin 22 when powered off. Which sounds correct as the battery pack is putting out the same. When I check with power on I get 5 volts which sounds correct.im at a loss with this I replaced the 5011 chip twice I guess it could be possible I got 2 bad chips when I purchased them. I don’t know what else to check beside buying a few more chips...

I think I narrowed it down to the Z1 chip. I measured the voltage from a good board and Pin 1 on Z1 should measure 4volts (at least that’s what the good board measured) the board In question is measuring 0 volts. I changed Z1 with a known good chip, and it still measures 0.. where does pin 1 on Z1 get its power from? Where should I looking?

Thanks Raff,
I had just ordered a few more 5011 chips, hopefully your correct.
But I have my doubts. Since I changed out a couple I already had from
Docent.
I guess they could all be bad (anything’s possible)
From what I understand about these chips, you must handle them very carefully.

Voltage is good at pin 22, Yes I did the ground mods, thanks for your help on this, I’m now waiting on my new 5011 chip I ordered today...keeping my fingers crossed

Well I changed the 5011 chip again ! Same thing the audits still won’t hold correctly.
And it only accepts 1 credit. I tried evything I can think to do and everything you guys
suggested to do, but no change. I’m now thinking it’s the spider chip that’s fried.

FOUND THE PROBLEM!
Turns out 4 of the 22 traces on the 5011 chip was bad. I figured let me take off the socket and take a good look.
Four of the eyelets were gone. So I soldered wires on the back of the board and it worked. It doesn’t look the best but it’s a working backup board... thank you guys for your direction on this problem....