I'm trying to help a guy fix his KISS.  I haven't really worked on any machines from that era yet and am looking a little direction.  Long and short of it seems to be that it gets power when turned on, but doesn't engage and one of the target lights (A) stays on.

The MPU was just replaced with a new one yesterday in an attempt to fix the problem so it's probably not that.

Any suggestions would be great, thanks all!

How many flashes are you getting off the MPU led?

Not sure (at work right now).  I'm guessing there's like a number of flashes to whatever the problem is ratio then?
  

Definitely.

Cooke is the best I know with these machines, but counting the flashes is always the best place to start  

http://www.pinrepair.com/bally/index2.htm#flash

OK... here goes:

1- check for your 7 flashes of the LED on the MPU. If you don't have 7, please advise how many flashes you get

2- check ALL the voltages on your power supply. It is 32 years old and the one in Kiss was not the best. Chances are that a bridge rectifier has failed and your 5V feeding the MPU is not correct. If voltages are off you can repair it but replacement boards are only 55$.

3- if OK, disconnect all the MPU connectors EXCEPT the bottom left one. Do you get your 7 flashes now? (this isolates the MPU from all other components that could be shorted)

4- If the power supply is OK, measure the 5VDC at TP1 on the solenoid driver. If it is of correct value, set your multimeter on the AC setting and check it again. This will check to see if your big capacitor on the solenoid driver is filtering any AC ripples in your 5VDC feed. A good reading would be way under 0.100V.  Anything close or over that would indicate that the capacitor has failed or dried up and is weak. This can freeze up an MPU easily.

Let's start with that...

Great stuff guys, thanks a lot.  Will give it a go and check back in.

Just heard back from the machine's owner and apparently the MPU is one of the new Alltek boards and he isn't getting any flashes.  The LED just stays solid green.  Sent him sparky's 4 steps so hopefully that will help.  

At least if it's the MPU it's backed by a lifetime warranty  

If the LED stays solid ON with a brand new board (and proper EPROMs/jumpers/switches)
then the issue is related with either:
- no +5V supply from the solenoid driver (but +12 present since LED lit)
- bad pins in the MPU's J4 female connector, or bad J1 pins on the solenoid driver's connector
- check the raw unreg supply from the rectifier board.

Cheers,
- Sylvain.

Quoted from sylvain

If the LED stays solid ON with a brand new board (and proper EPROMs/jumpers/switches)
then the issue is related with either:
- no +5V supply from the solenoid driver (but +12 present since LED lit)
- bad pins in the MPU's J4 female connector, or bad J1 pins on the solenoid driver's connector
- check the raw unreg supply from the rectifier board.

Cheers,
- Sylvain.

Yup. My money is on a power supply board with a fubar bridge rectifier...

Quoted from Sparky

2- check ALL the voltages on your power supply. It is 32 years old and the one in Kiss was not the best. Chances are that a bridge rectifier has failed and your 5V feeding the MPU is not correct. If voltages are off you can repair it but replacement boards are only 55$.

Any leads on where this board can be found for $55?  Seen a few just poking around the net but not anything lower than $80.

Quoted from dancadera

Any leads on where this board can be found for $55?  Seen a few just poking around the net but not anything lower than $80.

I don't know if one is better than the other but the GPE one is working fine in my Catacomb BUT I think that GPE also throws in new fuses, connectors and contacts which is a nice bonus. Shipping is always very fair too.

http://www.greatplainselectronics.com/proddetail.asp?prod=135-104

http://www.rottendog.us/BPS018.htm