(Topic ID: 32480)

Gottlieb System 80b MPU question SOLVED


By Natetheviking

6 years ago



Topic Stats

  • 16 posts
  • 6 Pinsiders participating
  • Latest reply 6 years ago by ChrisHibler
  • Topic is favorited by 2 Pinsiders

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#1 6 years ago

So, I recently bought a Genesis which I understood wasn't exactly booting when I got it. He told me he had gotten it to boot by pushing on the piggyback chip on the MPU. I tried this myself but couldn't get it to do anything. So, I pulled the board out and removed the piggy back chip and found that along with a few lifted traces the position and pins where that chip plugs in is darker than the rest of the board. There's also a sort of residue around the pins. It almost looks like glue or something.

So, what is this indicative of and what steps do I need to take to correct it. ?

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#2 6 years ago

Looks to me like somebody reflowed the joints at some point

Unfortunately, those aren't the joints that are problematic. It's the ones on the daughterboard.

Desoldering the board can be a bitch. If you don't have the proper tools (i.e. real desoldering equipment) its easy to lift the traces. Proceed with caution or send it out to one of the reputable board repair guys.

#3 6 years ago

I would say that whomever soldered the chip holder in, heated it up to much is why the traces are lifted. The discolorization may be flux residue which can be conductive in itself and should be cleaned using alcohol and a Q-tip. Clean both sides of the board. That fact that he says the machine boots up when he pushed on it leads me to believe one of those traces may be broken, or if luck is on your side mabe the chip was not inserted securely and just needs to be reseated. Look at the chip pin legs as well to see if they are damaged in anyway as they are prone to bending and breaking off if care is not used when being popped in. I would also check each trace for continuity from the pin location to it's location on the connector pad of the board itself. Hope this helps, keep us posted' A worst case senario would be you may have to jump a trace or two or you may have problems with your reset section on the CPU (located directly below the battery location if original) which in that case may need to be rebuilt. Oh BTW be sure to reseat all the connectors leading to and from CPU board.

#4 6 years ago

If you don't have significant experience repairing boards with delicate traces, you should strongly consider sending it to a pro.

What you are seeing is most likely flux residue. Since you've already identified pulled traces, the job will be a bit tougher than normal. I absolutely love this reproduction board from GPE...
http://www.greatplainselectronics.com/proddetail.asp?prod=140-101

The reason I like it is that you can solder two quality machine pin sockets into the U2/U3 position while attached to the repro board. This ensures that the pins line up. The repro board is engineered to include redundent connections between all of the pins possible. Awesome product.

If you want the board repaired professionally, I can take care of that for you. I've done dozens of these, along with just about any other pinball circuit board. Send a PM if you'd like me to help.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#5 6 years ago

Is the daughter board supposed to be soldered to the main board? I seem to recall something in the manual indicating something like this. At any rate, it definitely isn't. I'll clean the thing tonight when I get home from work and see if I get lucky.

Thanks for all the help; I certainly appreciate it.

#6 6 years ago

Yes. From the factory, it was soldered to the main board. Is your daughter card in a socket?
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

#7 6 years ago

I'm not entirely sure how to answer this. Yes, it plugs into something that holds it into place on the board. It's seems like a loose fit. Do you mean that the socket would be a post-factory modification?

#8 6 years ago

Looks like clear lacquer nail polish on the back of the pcb to me...

#9 6 years ago

It's more likely resin from the solder. It should clean off with some denatured alcohol.

#10 6 years ago
Quoted from Natetheviking:

I'm not entirely sure how to answer this. Yes, it plugs into something that holds it into place on the board. It's seems like a loose fit. Do you mean that the socket would be a post-factory modification?

Post a picture of where the daughter card meets the main PCB. Do it's legs solder to the board, or do the legs insert into a socket?
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#11 6 years ago

I misremembered exactly which picture I was taking when I was taking them or I would have gotten a closer shot of it but there if definitely a socket there. And those legs are a little shaky.

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#12 6 years ago

Thats not stock. It's not necessarily bad, but it's not stock.

If you have any movement on those socket legs, it'll never work reliably. Since the daughter board is easily removed cuz of the sockets, it might be wise to just buy one of the GPE solutions that Chris posted earlier. Even if the female part of the socket on the mpu might still have problems you'll still have the redundant solder points ( above the socket on your mpu) that are probably unmolested and you should be able to get a good connection there.

That's probably the cheapest, easiest solution with a pretty high probability of working.

#13 6 years ago

I've never been crazy about that type of socket, I always go for the milled type instead, they tend to make a better connection over extended use.

System 80, not just a job, it's an adventure

#14 6 years ago

That's a hack.
Clean that up with one of Ed's repro boards.
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

2 weeks later
#15 6 years ago

I'd been meaning to post a followup to this question but, of course, with the holidays I got sidetracked by everything.

Me and a buddy of mine got the board installed but what wasn't exactly clear in the pictures was the level of acid damage on the board. It didn't look too bad to me but was probably a contributing factor. At any rate, installed the daughter board, and added a battery pack, jumped that one trace you see in the photo and now it's running like a champ.

Thanks again for all the help.

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#16 6 years ago

Thanks for closing the loop. Nice to see another pin brought back!
--
Chris Hibler - CARGPB #31
http://www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm
http://www.PinWiki.com - The new place for pinball repair info

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