Dreaded acid corrosion - Some success?????

[Retropin]

I bloody hate this.

Ive been chasing my tail on a non booting zaccaria CPU board. Mike "homepin" came round yesterday and gave me a new set of eyes on the board. Within minutes he had spotted a fault that i had looked at time and time again but not seen.
So today i stripped the board back, took off some sockets, removed a 2114 RAM that i was very hesitant to do.

I had earlier managed to remove without damage a 2114 RAM from some old arcade boards i had lying around ( great for spares!!).. so i was happy to cut the original away.

At first sight, all looked good, till i did a continuity test through the traces.
 Board had seen some acid damage, but i cleaned it up.
The 5416(?) RAM was socketed... chip looked good, but i replaced the socket.
2114 RAM was soldered to the board.

Circuit in question can be seen here



Close up




The traces have been eaten away around the solder pads, so socket would solder OK, but signals go nowhere!

I look at this circuit and i just groan. Ive chased acid damage on Bally boards before and spent bloody hours and hours cleaning them up, testing, replacing components and the damn things still dont work.

This circuit is going to be a bloody pain.... ive since tested the top half of the board and most of the pads are floating.


Finding replacement Zac boards aint easy.... fixing this corrosion is a pain.. ill never be 100% that ive covered everything.


Please remove and change batteries regularly... kills a game completely

[FirePower]

That's a pretty tough fault that needs a very good eye to see ....  as you say, change your batteries is the message.

[Homepin]

might have to make a blank Zac MPU after the Bally one.....

[Retropin]

might have to make a blank Zac MPU after the Bally one.....

LOL!!! Go for it Mike.

Ive got no choice but to tackle this corrosion... my problem now is if i do all this work and the CPU still does not boot then i cannot be sure that its still not a corrosion fault... ..................

But!!! Had i spare blank Zac board.. then guess what my next job would be?... and made with confidence that all is complete.

[Strangeways]

Corrosion is a bitch - I've done my fair share of Bally / Stern MPUs. Still - it is a challenge. Make sure you neutralise the corrosion with a solution of 50/50 water/white vinegar. Then wash with alcohol.

At least you found the potential problem - well done Mike for saving some of Gavin's hair !

[ddstoys]

 I feel your pain Gav I have a few Bally board with the same issue sitting in the one day pile and I'm currently working on a stern with similar issues.  Even with the test Rom no flashes but everything seems to buzz out greeted

   GOOD LUCK MATE

[shansta]

Those solder pads: ouch!  

Have you talked to Jomac?

Be surprised if Joey can't help you?

[Steevsee]

Any chance to repair the PCB?

I've been looking at some PCB repair kits online. Some of the repair videos on this site are amazing. http://www.solder.net/PCB/pcb_repairkit.asp

[ajlaird]

If you have a steady hand and good eyesight or a magnifying glass, you can fix this sort of thing with single strand wire and a lot of patience.

But I am not sure I would attempt it...

[ddstoys]

What Andrew said is spot on strands of copper wire create great traces you cut them roughly to length feed it through the hole and bend it into shape if the pad runs both ways you gently widen the hole and repeat the process for the other side.   

  Definately need patience but can be done.   But therefor always that doubt have I done it right has the acid damaged gutter under the sealer  . Wish people would just chance the batteries

[Retropin]

The board will be repaired.. ive done it all before but bloody hate the job.
I could have sent it out for repair right at the start, but whats the fun in that? I deliberately wanted a non working Zac game cos it screws with your brain when fixing them and i wanted a challenge.

Be careful what you wish for..

[pinnies4me]

Even changing the batteries doesn't guarantee you're safe. Chewed up the board in FH a few weeks back with Duracells that were less than a year old. I've added remote packs to all the games now except one at a mates I'll get to this week.

[Dutchy]

Do it mate,
It's "only" hours ...... but it's like brain surgery on a pin, pretty satisfying when it works, go on give it a try

[johnwartjr]

Corrosion repair is not my favorite thing to do.

FYI, battery leakage on pin boards is from a *base*, not an acid.

Time to run some jumpers, or get a trace repair kit

[Retropin]

Well a few hours work and some painstaking soldering with a nice pointy tip has given me this result.
Im not sure its "pretty" but at this stage i am sure its 99% correct. Ive buzzed the cct out twice so far but my eyes are tired and i know im either making or close to making mistakes, so ill buzz again tomorrow before im prepared to put the 100% correct tag on it.
Oh man theres some irritating fine trace work done here.
I took the board back beyond the corrosion and reworked it all using single trace copper strand. Some of the traces go 2 ways from the chip sockets, so 2 strands were inserted and then soldered along the track. Some i couldnt get to, or the risk of shorting logic paths was too high so i went along the back.

hate this work... but it done ( i hope!!!!)