Hi All,

I'm looking for some guidance on a Firepower MPU. I have it removed from the game and powered up with an old PC power supply providing 5vdc and 12vdc. I also just purchased Leons test ROM and have that installed.

When powering up, both LED's turn on once them off. They stay off after that, no blinking as expected. When pressing the diagnostic switch, the LED's do nothing.

Also, I connected a LED to Pin 15 of the CPU and it blinks quickly, but nothing from the LED's on the board. It appears that the board is booting up enough to turn off the LED's, but not completely running. Any ideas what I should check next?

Thanks for the quick reply. Yes, I've removed the MPU board from the machine and am testing it without the driver board. I connected 12vdc to pin 9 of 1J2 which should accomplish the same thing as the jumper.

A quick update, I was checking the outputs of the PIA and pins 2 through 17 were all low and not pulsing. When I would power up the board, I would see each output flash high briefly then stay low. Which makes sense since the LED's would flash on then stay off and makes me think the PIA is ok. The control LED connected to Pin 15 of the CPU is flashing and there is a lot of activity on the input pins to the PIA.

Well now the odd part, I walked away to grab some lunch and when I came back, the LED's were flashing. I pressed the diagnostic switch and it passed the memory test.

So it looks like there must be a back connection somewhere. I already checked for cracked solder joints and don't see anymore. To help narrow it down, what would cause the PIA to set all the outputs low, while the CPU is running ok? Could this also be a flaky chip?

Where is a good place to buy them? I want to make sure I buy good quality ones. It also looks like I'll need a new switch matrix PIA, I was doing some checking on my driver board and it's no good. Any suggestions on where to get those as well?

Ok, new problem. When I power up the MPU the test LED at pin 15 of the CPU blinks sporadically. Fast, slow, no rhythm and locks up occasionally. Any idea's where to start? I have the MPU on the bench completely removed from the backbox and driver board. I have all the ROMs and Cmos removed and only Leon's test ROM installed. Also, when it's in the machine with the game ROMs (with Fuses F2 and F3 removed), both LEDs lock on with no flashes and it repeats the word "Firepower" over and over.

Yeah, I replaced them and tested in the bench (both MPU and driver connected) and it worked great. I put it in the machine to test it out and it worked for about 10 seconds before it started saying Firepower on repeat. Now I've removed it and the MPU board is not working again.

Had a few spare minutes and found Pin 5 of IC1 is stuck High, I believe this is supposed to pulse?

Bump.

Does the fact that is says Firepower on repeat at power on help narrowing down where to look?

I should note that the MPU board was working on the bench, then I put it in the machine, it went into attract mode for about 10 seconds. Then the display's went out and it started saying Firepower on repeat. It no longer works on the bench after that. Is it possible something got fried?

Thanks for all the replies. Yes, the 40 pin interconnect has been replaced. It looks like I actually have 3 separate problems which is why I've been pulling my hair out.

1st, my test EEPROM is bad. I got fedup, so I put my game roms back in, connected the MPU and Driver board and fired it up. The LED's blinked once and turned off. I pressed the diagnostic switch and they blinked twice and went off. Looking better already.

2nd, the game repeats firepower over and over. Ill address this issue later separately

3rd, there is no blanking signal. This is the issue I need to fix first, but need some help on how to troubleshoot it. I checked Test Pin 4 on the MPU and get 0 Volts. Where to go from here?

No pulse with the probe scope, just staying low.

None of pins 2-5 are strobing; pins 2, 4 and 5 are stuck low, pin 3 is high. All pins 21, 23-33 and 35-36 are strobing.

Yeah, the LEDs flash on then turn off when powered on. They also flash twice and turn off when the diagnostic switch is pressed, so it seems the like PIA is working.

I replaced the PIA sockets on the Driver board, but not the ROM sockets on the MPU board. Since it boots and passes diagnostics, I figured these are ok? They are RN, not Scanbe. I can order some up if that could potentially be the problem, but would also like to keep troubleshooting while waiting for them in case it doesn't solve the issue and I lose time.

I'll get some ordered up

CPU pin 4 is pulsing.

I'm looking at the MPU schematic to see where to look next, but am not sure where to go. I need to better understand what makes the PIA at pin 4 generate the pulse.

I'm assuming that the CPU is working and the game ROM is loading and running. I say this because the LED's flash on then go off, and also pass the diagnostic test. Also, everything passed with Leon's test ROM.

I'm also assuming PIA at IC18 is ok since it passed with Leon's test ROM.

But, IC18 pin 4 is low instead of pulsing. If the above is correct, then I am assuming the PIA is not being "told" to generate the pulse for the blanking signal. What "tells" the PIA to generate this pulse?

So this is embarrassing. I made a rookie mistake. I didn't realize that after pressing the diagnostic switch that the power needed to be reset to put it back into attract mode. I must have pressed it before measuring the blanking signal.

Once I realized the mistake, I popped it back in the machine. And it locked up. Since it worked perfectly on the bench I figured it must be the power supply. Sure enough the connector had some bad joints. I replaced it and she came to life in attract mode!!

Now it still won't start a game. I can add credits and there are 3 balls in the trough, but no game start. I ran it through the self test and the displays and lamps work great, but the solenoids will not fire. The sound solenoids 9-13? work, but none of the coils. Any ideas

Fuses are good and in place. 40 pin connector was just replaced on both the driver and MPU board. I also put in a new battery holder and batteries. Reading 4.4 volts and diode checks out ok.

I thought if there was an issue with the batteries or cmos that it would start in audit mode? I'm starting in attract mode, so I figured the batteries and cmos were ok.

Ok, I checked the fuse and it is blown now. I swear it wasn't blown when I checked it earlier, but it is now.

Also, It stopped working and locked up again. I checked the logic voltage at the MPU and it was low again. I removed connector J6 on the power supply and the voltage was good there. I reseated the connector and the machine booted into attract mode. So I will be replacing the connector on the wire harness (I replaced the pins on the board yesterday)!

With the machine booting again, it now lets me start a game. Of course, with the solenoid fuse blown, none of the solenoids work, but everything else checks out (displays, lamps, flippers etc.).

The only other funky thing going on is the middle coin switch adds 4 credits each time it's pressed. The left and right each only add 1 per press. Any ideas on this and where to look for the cause of the blown fuse?

Doh! Good to hear, because I was worried it was some impossible to find wiring issue!

Thanks for the advise, I was only securing with the top 2 screws since I was taking it out often, but will make sure it is properly secured so I'm not chasing my tail.

Well she's up and running, just played a few games!!

The fuse must have blown when the game locked up with the bad connection or something. I put a new fuse in and it fired right up.

Moral of the story (as has been documented many times) don't mess around with the connections, assume they are all bad and resolder/replace them.

My last question (I hope for now) is what is the best way to adjust the switches. Two of the switches in the trough don't always make contact when a ball is in there. I ran some trials and it misses the ball about 1 out of 9 times. It's kind of a pain to not be able to put the next ball in play or not be able to start a game randomly.