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Aussie Pinball Forums => Technical Matters => Pinball Repairs / Problems & Assistance => Topic started by: vinito on January 02, 2009, 10:41:53 AM

Title: Bally MPU-35 corrosion repair tip (NGS)
Post by: vinito on January 02, 2009, 10:41:53 AM
Woohoo! I got my brother's Nitro Groundshaker up & running today. Only a matter of time now before I shop it and get it out of here so I can drywall the room it's sitting in. It's got a Space Invaders sound rom in it so I need to get the right one in there, but other than that it seems OK.

The tip:
If you get a corrosion repair kit to refurbish the MPU, be sure to notice that the C5 capacitor is polarized and install it correctly!!!
I even noticed it was polarized from the schematic early on and still overlooked that I installed it backwards, which caused it to keep locking up. FINALLY discovered the problem today and quickly remedied it in about 30 seconds after wrestling with it for a couple weeks or so.
 @.@

Won't be long now.
Title: Re: Bally MPU-35 corrosion repair tip (NGS)
Post by: Strangeways on January 02, 2009, 10:51:58 AM

I used to collect and repair MPU -17 and -35 to repair for "fun".. Just "pass time" for 30 hours replacing the sockets, installing new chips, installing the corrosion kit from GPE and then fixing all the broken tracks ...

 :D

All I can say is if you can fix these boards, you can fix anything.. I still have a pile of them in a corner.. "one day" !!


Great to see you have fixed the board Vinto. After spending all the effort repairing the board, I know the feeling when it does not boot..

I remember a Stern -200 board that I spend hours on - It would not boot in my test rig, but it worked perfectly in the machine !!
Title: Re: Bally MPU-35 corrosion repair tip (NGS)
Post by: pinnies4me on January 02, 2009, 10:52:06 AM
FINALLY discovered the problem today and quickly remedied it in about 30 seconds after wrestling with it for a couple weeks or so.


Probably quicker than Tony is going to find that shorted lamp socket though!   :lol :lol :lol :lol :lol :lol :lol
Title: And now... for my next trick
Post by: vinito on January 04, 2009, 04:34:34 AM
Since I have a guru and a little more experience, and since Strangeways says I can fix anything now *)* I ought to dig out the damned TZ sound board that I never could figure out. I ended up replacing it, but of course I don't have the heart to toss it. Maybe if I can get it working I'll sell it for exorbitant profit and split it 50/50 with Joe (the guru). Nah. I guess it really ain't easy bein' green.

I left it on for several hours and played a game now & then yesterday, then went ahead and hooked up a remote battery pack for memory too, so I guess I can say with reasonable certainty that the MPU rebuild is a success. What a relief.
Title: Re: Bally MPU-35 corrosion repair tip (NGS)
Post by: pinnies4me on January 04, 2009, 09:25:38 AM
Well done!