(Topic ID: 253657)

Bally MPU -35, problems with booting (no LED flashes)

By frsj8112

5 months ago

Topic Stats

  • 9 posts
  • 4 Pinsiders participating
  • Latest reply 5 months ago by frsj8112
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#1 5 months ago

Ok guys, i've been working on this Bally MPU -35 board for a few days and it's driving me nuts.

The original Frontier ROM set was not working properly, EPROMs (2716s) were bad, so i converted the board to 2732, so that I could use the EPROMs I had in stock.

Now I can get the board working on my testbench (JAMMA switching PSU) with +12DC, +5DC and ground.
I get 6 flashes on the LED and all seems fine.

When I put the board in the cabinet, the LED gives the initial flash and then it halts.
Put it back on the JAMMA-rig, and it works again.

What in the lords name is wrong???

#2 5 months ago

Bad 12 volts?

#3 5 months ago

I've tried the MPU board from my known working Vector machine and when running that board in the Frontier machine it works like a charm.

#4 5 months ago

Replace J4 header and connectors.

#5 5 months ago

Is 5v possibly a bit low?

#6 5 months ago

It’s weird though when the Vector MPU works fine in the Frontier machine

#7 5 months ago

Measure the 12v and 5v when the suspect board is installed. There may be a short that is loading those voltages down.

#8 5 months ago

I tried the board today in the Frontier machine using Leons test rom and it worked as it should, it was pulsing the LED.
Then I switched back to the Frontier ROM set (2732's) and it did not boot. Tried flicking the power switch a bunch of times and all of the sudden the MPU booted!?

Powered off the machine again and powered it on and it stopped booting again after that.
Really weird

#9 5 months ago

I repatched the MPU so it can use 2532 EPROMs instead and now it works like a charm. Really weird but now I'm happy again

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