(Topic ID: 273033)

System 11B MPU No boot, U54, U51 and U42 Errors After Acid Repair Help


By Oldschool77

9 months ago

Topic Heartbeat


Topic Stats

  • 11 posts
  • 3 Pinsiders participating
  • Latest reply 9 months ago by Oldschool77
  • Topic is favorited by 1 Pinsider

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#1 9 months ago

I'm gonna try to keep this shorter then most my other posts...if you need more details let me know please.

So long story short.....my Space Station I bought a couple weeks ago worked fine (other than a bad trace for the audio, that I quickly fixed), had no issues, but it had light acid (alkaline) damage. Very light, basically it had dulled the solder on the two PIAs below the holder and the one to the right (U41, U42 and U51) and had a little bit of residue on them and a few other components (See area circled in red....those are everything i replaced)....

This was my first corrosion repair, but i consider myself a decent to good solder/repair person with a good amount of experience under my belt with component and chip replacement.....as you can see in the pics....everything was removed, lightly sanded down to copper, trace continuity was verified.....everything installed....continuity verified again (through the sockets), including to the pins next to each other to verify no solder bridging to the one next to it....and then all the chips installed....put it in the game and turned it on and i got a solid 5V light, no blanking light and codes 3, 5 and 7 flashing on the diagnostic light.

3, 5 and 7 are faulty U54 (U54 was not replaced...looks perfectly clean), U51 and U42 (Not necessarily in that order, i don't have the code chart in front of me, but the flashes were 3,5, 7 in that order).

I have a fully working Earthshaker MPU with me that I borrowed from a local buddy to compare things to....i'm sure i missed something and obviously i created some sort of problem. I don't see any solder bridges anywhere (I verified as each component was installed).

Things to note....

I replaced D2 with a "beefier" Diode (all i had on hand, i missed the corrosion on it when i placed my order)
I re-used C57 (It looked fine, Marco sent me the wrong value of the one i ordered)
And i accidentally cut a trace for U49 (Circled in black in the one pic) so i jumpered it on the backside and verified continuity.

Thoughts?? Obviously i screwed something up....what would be a common failure point of the things i touched that would cause all three of those PIAs to "appear" bad?

Thank you!!

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#2 9 months ago

Here's a couple pics after i rebuilt everything, but before i re-installed the chips...

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#3 9 months ago

Make sure that all the chips are the right way.
Did you measure continuity with the chips in (measured from the legs of the chips)?
Do you have a logic probe? If so, start looking for stale pins on the chips.

#4 9 months ago
Quoted from RonaldRayGun:

Make sure that all the chips are the right way.
Did you measure continuity with the chips in (measured from the legs of the chips)?
Do you have a logic probe? If so, start looking for stale pins on the chips.

Double checked last night.... I found a trace I cut this time... Jumpered it and now things are better but not good. Now I get no error codes, the diagnostics light is flashing quickly as it should but I get no blanking light and no boot up. Interestingly I did get the adjustment failure sound the first time I turned it on which is correct because I replaced the battery. But that's as far a it went. So now I need to find out what I messed up on the blanking circuit.

#5 9 months ago
Quoted from Oldschool77:

acid (alkaline) damage.

Can't be both because it would cancel out. Alkaline damage is the correct term here.

#6 9 months ago
Quoted from Oldschool77:

I found a trace I cut this time... Jumpered it and now things are better but not good. Now I get no error codes.

Which trace? This is very good information got others to know.

Also, replace C30 22uf 16v, as this can cause false error codes. Electrolytic capacitors only have a life span of about 15 years. There are others as well that should be replaced. After all this work,I definitely would had installed 6116 NVRAM.

#7 9 months ago

The blanking signal going out to the display, I believe, should be high. Should be easy to spot on the schematic. Test the signal at all places to see where is is broken.

#8 9 months ago
Quoted from PinballManiac40:

Which trace? This is very good information got others to know.
Also, replace C30 22uf 16v, as this can cause false error codes. Electrolytic capacitors only have a life span of about 15 years. There are others as well that should be replaced. After all this work,I definitely would had installed 6116 NVRAM.

Thanks... I picked up all those caps I just haven't installed them yet because I want to get the board running first. Everything ran 100% a few days ago before I started taking it apart to fix the damage so I feel like the caps are probably okay even though I'm still going to eventually replacethem. I know it's gotta be something simple that I cut or messed up I just haven't found it yet lol. Comparing everything to the working earthshaker board, everything matches so I'm missing something.

#9 9 months ago
Quoted from PinballManiac40:

Which trace? This is very good information got others to know.

It was the one for pin 7 under U42...cut right before the thru hole, this cut out the other two PIAs too. Which is why they all were being reported as bad.

1 week later
#10 9 months ago
Quoted from PinballManiac40:

The blanking signal going out to the display, I believe, should be high. Should be easy to spot on the schematic. Test the signal at all places to see where is is broken.

Were you able to follow this on the schematic?

#11 9 months ago
Quoted from PinballManiac40:

Were you able to follow this on the schematic?

Not with any degree of accuracy....I eventually threw my hands up in the air and sent it off to Chris Hibler. I'll report my findings once he figures out what i did wrong. I do know that every single trace I touched has continuity AND that I didn't flip any chips or get any components out of location. So i'm genuinely curious what his findings will be.

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