(Topic ID: 37804)

ToM CPU: Acid damaged?

By NJGecko

11 years ago


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  • 29 posts
  • 11 Pinsiders participating
  • Latest reply 10 years ago by NJGecko
  • Topic is favorited by 1 Pinsider

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#1 11 years ago

Wondering if acid damage can just cause oddities. Seeing some weird behavior with my ToM I'm restoring and thinking it may be acid damage. But is that more of a "work or don't work" scenario or a "weird" type?

For example, things registering on some switches causing improper behavior (game locks a ball, then ejects it, but still thinks its locked), game won't hold the trap door open (which uses the hold transistor which is CPU controlled), and some other odd stuff. I have checked (and replaced) any questionable transistors.

There was some acid damage to the battery holder, but I replaced it. I didn't think it got onto the board since the WPC-S used the off-board holder. See pictures below.
Not sure, beyond replacing the headers, where i should go with this. The lower portion of the entire board looks discolored which concerns me.

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#2 11 years ago

That does look like damage to some of the parts ( solder joints ) and headers.

You need to remove the headers and clean under them too.

LTG : )

#3 11 years ago

That diode on the left of the top pic does not look too good either.

#4 11 years ago

I'm going to see if I can swap a different power driver board in and see if the problems remain or not. Not sure if it's worth trying to chase down issues on this board or not if it's got issues that aren't immediately evident or not....

I may have to just order some replacement components and go from there. Does it make sense to just try to resolder any parts that test good just for good measure?

#5 11 years ago

You can see the acid corrosion on those pins, especially that 7 pin header above switch inputs.

#6 11 years ago

Yea...I'm going to at least do the headers, I might as well do all of the headers. It's the other components I'm unsure about. They all seem to test OK, but the solder from a bunch of them has corrosion on them, so those are what I'm unsure about. Just resoldering them may be a good first step I guess?

#7 11 years ago

Well if you look at the back of the board down by where that notch is cut out a lot of the solder pads have that dull look as if they've had the surface stripped off. You can really see it if you compare it to those around it and how shiney the pads look in comparison. May just be the pic and angle of light but it looks like the surface of some have been stripped off.

#8 11 years ago

You're correct. The lower corner definitely has had some acid damage. The question is can I just reflow those joints? Or what's the best way to handle it? I could break the hakko out, unsolder them completely, and resolder with "clean" solder. Is that a valid course of repair or should I replace every component that's got a dull pad? As I said, the components themselves all seem to test OK from their leads.

#9 11 years ago
Quoted from NJGecko:

The question is can I just reflow those joints? Or what's the best way to handle it?

I'd think reflowing would be good but you might want to get an opinion from someone with more knowledge than myself. Should you desolder completely I'd be damn sure to test each componet off board, as I've heard of them testing good on board, but actually being bad, and not discovered until they were removed. Someone will get on the site here that can give you a better direction to go I'm sure. Good luck and keep posting results and what you've done to achieve them.

#10 11 years ago

I'll see if anyone else jumps in. I know that the traces are delicate on here, and I want to minimize the heat cycles I expose the board to. I'd hate to heat, desolder, resolder, and then wind up finding a bad component and have to do it again. I need to just make a shopping list and order up the replacement components I suppose...for $15 worth of components, it seems silly to play around.

#11 11 years ago
Quoted from NJGecko:

for $15 worth of components, it seems silly to play around.

Wise words!

If you've never done or have little practice working on boards grab anything old not working and pull the board and practice. It gets easier as you go...

#12 11 years ago

What you don't show in your pictures, is how much acid damage do you have on the chips just below the battery holder. Can you show some pictures of that area to us? For sure, you can have random switch failures. I worked on a machine recently where the acid damage on the MPU caused at least 9 switches not to work at all, including the start button. I can see you spending well over 8 hours removing parts, cleaning the board and reinstalling NEW parts.

Personally, I don't waste my time fixing extensive acid damaged boards as you have there.
A new PinLED WPC-S board is the way to go.

http://www.pinled.de/shop/product_info.php?cPath=2_12&products_id=124

Actually installed one in a TOM for someone a week ago and it works very well.
The board is only $191.70 delivered if you buy the board without the ASIC chip.

One thing you definately don't want to do is risk changing bulbs with the machine on. If by chance you short out a bulb socket to the switch matrix as this will damage the "U20", which on this board will be surface mount so it will be a fun one to replace for sure.

Other than that, there is a NVRAM chip so no batteries are on board. Well, because of that the clock will be inacurrate, so you will then need to not display date/time.

Then resell your acid damaged board on Ebay to offset some of that cost of buying the new board.

#13 11 years ago

I've worked on boards plenty...me and the Weller are good friends I'm just trying to figure out the best way to resolve what may or may not have have happened to this board.

#14 11 years ago

Thanks Maniac...I'm really trying to not cough up the $200 for a new board if I don't have to. Figure I'll try some steps first before I go that route. $20 worth of parts and some time with the iron are worth it to me to at least try.

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#15 11 years ago

Well, if you are that bored, and have the time, it will improve your soldering skills for sure.
I see acid damaged MPU boards go over $80 at times. Soon, I'm going to be posting on Ebay the MPU that I replaced out of that TOM machine I worked on.
With 33 machines in the house, 15 being project games, I know I don't have the time to work on such time-extensive boards.
Though, it is fun bringing boards back to life.

#16 11 years ago

Yea...with 33 machines, that'd qualify as a different level than I am at

#18 11 years ago

Thanks. Good watch.

#19 11 years ago

Jersey Gecko,

It's alkaline damage. Alkaline batteries leak alkaline. Alkaline is neutralized with acid, like vinegar. This concludes our chemistry session.

Sorry to be the bearer of bad news, but the board is toast. You can see that the alkaline has invaded much of the board below the solder mask. Those are the darker colored areas/traces that you can see. Every one of those needs to be exposed via sanding, neutralized with vinegar, and then repaired as required. Some of them will have been severed by the alkaline and will need to be rejoined.

You would be in for many, many hours of work, and in the end, if you leave =any= alkaline at all, it will mount a reattack, and begin eating away again. As John Wart characterized it recently, it's like rust on an old car. If you don't get all of it, it will come back. Rust never sleeps (Neil Young).

Pull the salvageable chips, and transfer them to a new board. Use what is left to practice desoldering if you wish.
--
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

#20 11 years ago

Chris,

Was hoping you wouldn't say that

#21 11 years ago

There's a slight chance that you might be able to find someone to repair this board. I know someone who had extensive corrosion repaired but the guy who did it is currently busy with the WOZ manual. Not sure how much he paid to have it done, most likely more than the price of a new Rottendog replacement. But I wouldn't neccessarily get a Rottendog so fast either, they are known to cause issues.

#22 11 years ago

Actually, I don't think Rottendog has a replacement WPC-S MPU for the TOM machine.
That is why I went with the PinLED MPU.

#23 11 years ago

I have someone recommended who is going to take a look at the board. They felt confident that it's repairable, but I just broke down and ordered a new one from PinLED. I just have a feeling I'm going to be chasing down odd issues with this board regardless of how well it gets cleaned up since the damage has moved between the layers and I don't think there is any easy way to neutralize it. It's just going to keep munching away....

#24 11 years ago

Nearly any board can be repaired - the question becomes if it can be *economically* repaired.

I am a member of an Australian Pinball Forum where one member repairs some heavily damaged WPC MPUs - he strips nearly everything from the battery compartment down, sands the board until he gets to clean copper on front and back, replaces everything below the battery pack, seals the board, runs jumper wires, tests, etc.

That's pretty extreme, and I've marveled at his results in the past. Often thought it might be fun to attempt such a repair in my free time - whenever it is I get some

#25 11 years ago

glad you ordered the new board hopefully you will have that game all done soon

#26 11 years ago

Expect 2 week delivery from PinLED (Germany).
Also, if there is any corroded pins on the bottom wired connectors, you would want to replace those as well.

#27 11 years ago

No rush from them. I'm hopefully going to get my original board back anyway, so it's a start!

2 months later
#28 10 years ago

Did you get the board yet and did you need to change any pins on the wiring as well?

#29 10 years ago

New board came in and was a plug and play install

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