Bally Solved Motordome (Bally, 1986) Help again

[EdGs]

Motordome Help again---Solved!

Hello again,

I am working on a motordome game where I had to replace the MPU board and eproms due to theowner shorting the power supply out.

After changing the MPU, the game worked allright except that the rollover switches above the pop bumpers were triggering multiple times. I tracked it down to the leftmost switch causing the most grief and changed it, also replacing the diode and the .05uf cap (with a .047, closest I could get)

Now I am getting all kinds of strange stuff. The MPU flash sequence hangs up between the 8th and 9th flash, then starts running. The display sometimes will blank out and/or freeze while scrolling across the displays. sometimes the pop bumpers fail to work or some switches don't trigger.

I am thinking that there are some connection issues on the MPU board, but didn't have time to check this further, and today was the first chance I had to work on it since a couple weeks ago.

I was very careful with the swich replacement, but this is freaking me out a bit.

Has anyone expienced issues similar to this on a 6803 system? thanks for any help you can give.

 

[EdGs]

Just an update, I found the source of the aforementioned problems. Turns out there are some funky connection issues with the molex plugs on the power supply module. I have found a combination of bad solder joints and/or bad pin to pin connections on the headers and plugs. I have replacements on the way and will advise of the outcome.

 

[EdGs]

I replaced the 4 molex headers on the psu board and all seems ok. It seems to me that a couple of the mating plugs for these felt slightly loose, but no issues. I have these connectors and pins in case they need replacement.

 

[EdGs]

This machine still had issues after replacing those 4 molex headers and their mating plugs and pins on the wiring harness, so I took another look through the board and ended up finding a definite cold joint on the header from the transformer.

It was on the phase a circuit for the feature lights, there was also one or two others that just didn't look right as well, so I replaced that header as well.

I am happy to report that this problem child is working excellent now. The lights on the playfield lit up like a christmas tree after it booted up. In fact. the owner said he didn't remember the machine ever lighting up like that since he's had it. I never saw it light up that way either.

 

[faralos]

on older pins especially always check the solder joints at their bases on the circuit boards
if you see even the smallest of hairline cracks that means you must resolder it to ensure a solid connection
buy a jewelers loupe so you can see the tiny solder joints easier
and always reseat any plugs on the boards as they may have vibrated loose
from moving the pin

 

[EdGs]

yeah, +1 on the loupe. The one on the transformer header I just simply missed- it was really noticeable. I also had gotten sidetracked because the 4 top connectors were relatively easy to plug in and unplug, and the locking tabs were very weak.

I was also thrown off because the problems seemed to happen more when the board was flexed around those 4 connectors. I would venture that both areas had issues becuse some of the solder joints there just didn't look clean and smooth.

I was pleasantly surprised when it booted and the playfield lit up. I went and got the owner and said "you've got to see this". I flipped the switch and when it fired up he said "Wow, it never lit up like that in all the time I've had it".

This machine is the first one I've ever messed with, so it's all a great learning experience for me. Now I want to buy one for myself....lol