Bally MPU problems

[graham]

Archived from groups: rec.games.pinball (More info?)

X-no-archive: yes
Hi folks,

Been working on a Harlem Globetrotters restoration for a while. Got a
replacement original Bally MPU installed, 7 flashes, all ok, goes into
attract mode - havent tested solenoids/switches yet.

Today, I was working on replacing bulbs/holders etc and after replacing
the playfield, I pressed the start button (note, this machine has not
been fully working, this was just the next series of tests).

Everything went dark, the MPU board now has just the continuous LED on
it (not even an initial flash). Powered off/on, still the same.

Started going through the Marvin guides (again), checked the reset
circuit - all ok, replaced CPU and 6821 at U11 but no go. Still to
check the eprom, some of the voltages at the CPU are a little on the
high side and there is nothing on pin 5 (clock).

Could it be the eproms? Marvins guide seemed to suggest U15 as a
possible suspect so I'll swap in another one of those.

Any other thoughts welcome.

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

First, have you verified good, clean 5 volts to the CPU board?
Is the large filter cap in the middle of the solenoid driver board still the
original?

-- Ed



"Graham" <me@privacy.net> wrote in message
news:3kijcoFu7iq5U1@individual.net...
> X-no-archive: yes
> Hi folks,
>
> Been working on a Harlem Globetrotters restoration for a while. Got a
> replacement original Bally MPU installed, 7 flashes, all ok, goes into
> attract mode - havent tested solenoids/switches yet.
>
> Today, I was working on replacing bulbs/holders etc and after replacing
> the playfield, I pressed the start button (note, this machine has not been
> fully working, this was just the next series of tests).
>
> Everything went dark, the MPU board now has just the continuous LED on it
> (not even an initial flash). Powered off/on, still the same.
>
> Started going through the Marvin guides (again), checked the reset
> circuit - all ok, replaced CPU and 6821 at U11 but no go. Still to check
> the eprom, some of the voltages at the CPU are a little on the high side
> and there is nothing on pin 5 (clock).
>
> Could it be the eproms? Marvins guide seemed to suggest U15 as a possible
> suspect so I'll swap in another one of those.
>
> Any other thoughts welcome.

 

[graham]

Archived from groups: rec.games.pinball (More info?)

GPE wrote:
> First, have you verified good, clean 5 volts to the CPU board?
> Is the large filter cap in the middle of the solenoid driver board still the
> original?

Yes, there is a good steady supply of 5 volts to the MPU board. The
filter cap looks original but I can't be sure. What is strange is that
the machine has been working, but after pressing the start button, it's
somehow killed the MPU board.

Any other ideas/thoughts?

Thanks
Graham

> "Graham" <me@privacy.net> wrote in message
> news:3kijcoFu7iq5U1@individual.net...
>
>>X-no-archive: yes
>>Hi folks,
>>
>>Been working on a Harlem Globetrotters restoration for a while. Got a
>>replacement original Bally MPU installed, 7 flashes, all ok, goes into
>>attract mode - havent tested solenoids/switches yet.
>>
>>Today, I was working on replacing bulbs/holders etc and after replacing
>>the playfield, I pressed the start button (note, this machine has not been
>>fully working, this was just the next series of tests).
>>
>>Everything went dark, the MPU board now has just the continuous LED on it
>>(not even an initial flash). Powered off/on, still the same.
>>
>>Started going through the Marvin guides (again), checked the reset
>>circuit - all ok, replaced CPU and 6821 at U11 but no go. Still to check
>>the eprom, some of the voltages at the CPU are a little on the high side
>>and there is nothing on pin 5 (clock).
>>
>>Could it be the eproms? Marvins guide seemed to suggest U15 as a possible
>>suspect so I'll swap in another one of those.
>>
>>Any other thoughts welcome.
>
>
>