Yeah yeah, I know it's been FOREVER since I've posted any updates in here. What can I say, I've been busy. 
This thread is going to focus on a Stern Whitestar MPU out of a LOTR. I had a member contact me just before the Ottawa show about his LOTR MPU, and how it had suffered some very very slight acid damage from leaking batteries a couple of years ago and it had been fine for a while but eventually stopped working. (hey, it happens to all of us at some point) I owed the owner a favor so I agreed to repair the board for him, and the story goes like this...
Normally the owner is diligent about changing all of the batteries in his games every year, but somehow LOTR got missed. He powered the game up and it gave him an error so he immediately checked the batteries, only to find they had started to leak. He pulled the MPU and removed the battery holder, washed the MPU in a 50/50 solution of water and vinegar to neutralize the battery acid, installed a remote battery holder and all was good. There was only slight visible acid damage to a handful of parts under the battery holder but the game still worked. Here is a pic (albiet VERY crappy, sorry) of the MPU as I received it. You can just barely see in the lower right hand corner around the CPU / ROM / RAM where the acid has done damage by the non-shiney solder.
Fast forward 12 months...
Eventually the game began to develop a booting issue. From what I was told the game would need to be power cycled, or the coin door opened and service menu's cycled before the game would boot properly, and it slowly became more and more frequent until the game stopped booting at all. At this point when the game was turned on, just the GI would flash and that was it. The owner called down to Stern for tech support and was told that it was most likely a bad trace somewhere, but even after having a few different sets of eyeballs look the board over nobody was able to see any apparent damage. So LOTR sat broken for almost another 12 months.
The owner gave the MPU to Warlock at the Ottawa show to transport back to me (thanks Scott), in hopes that I could get this repaired by Thanksgiving weekend. The owner would be down in the GTA area visiting family and could pick the MPU up while he was in town. After my own visual inspection I too did not see anything obvious that would indicate an issue, so I pulled up the schematics from Stern's website and sat down with my DMM and began to "ring out" and confirm every single trace between the CPU, the game ROM and RAM chips. All three of these are connected to each other and located DIRECTLY under the original battery holder! Low and behold, I ended up finding one trace between the CPU and the ROM & RAM chip that had gone open. (the trace between the ROM & RAM was fine) Now I wanted to find out WHERE it had gone open.
After looking at this particular trace between the CPU and the ROM I found that it started out on the top of the MPU (component side) but before getting to the ROM it travels through a via to the bottom (solder) side of the PCB. A via is basically a small hole in the PCB, and if you look at the first pic you can see a number of them below where the battery holder was and to the upper right of the CPU chip, they look like pin heads in the PCB as these ones got filled with solder during the mfg process. (some have discoloured from the acid) What happened was acid had leaked over this via, and coincidentally when it was washed with the 50/50 water & vinegar solution some of it got trapped inside the via. (they do not always fill up with solder) I know this because when probing this via with my DMM a tiny bit of water and vinegar actually leaked out! (It smelled of vinegar) Now for those that don't know, vinegar can also be harmful to your PCB over time as it's acidic, and is the reason we dilute it when neutralizing battery acid. What the owner failed to do after washing with this solution was to then wash the PCB in 99% isopropyl alcohol! (make sure it's 99%, as the 70% has too much water in it) This is important as the alcohol disperses any left over (trapped) water/vinegar from the PCB, and then quickly evaporates. So even though the original battery acid was neutralized, the trapped vinegar slowly ate away at the via causing the trace to go open.
Once all other traces were verified good, it was simply a matter of repairing the open trace with a small jumper wire shown in the following pic.
I then took the MPU to a local collectors house to test (as I do not own any new Sterns at the moment) to confirm my repair.
The board was picked up on Sunday, and hopefully another happy customer.
(I'm still waiting to hear from the owner)
D
This thread is going to focus on a Stern Whitestar MPU out of a LOTR. I had a member contact me just before the Ottawa show about his LOTR MPU, and how it had suffered some very very slight acid damage from leaking batteries a couple of years ago and it had been fine for a while but eventually stopped working. (hey, it happens to all of us at some point) I owed the owner a favor so I agreed to repair the board for him, and the story goes like this...
Normally the owner is diligent about changing all of the batteries in his games every year, but somehow LOTR got missed. He powered the game up and it gave him an error so he immediately checked the batteries, only to find they had started to leak. He pulled the MPU and removed the battery holder, washed the MPU in a 50/50 solution of water and vinegar to neutralize the battery acid, installed a remote battery holder and all was good. There was only slight visible acid damage to a handful of parts under the battery holder but the game still worked. Here is a pic (albiet VERY crappy, sorry) of the MPU as I received it. You can just barely see in the lower right hand corner around the CPU / ROM / RAM where the acid has done damage by the non-shiney solder.
Fast forward 12 months...
Eventually the game began to develop a booting issue. From what I was told the game would need to be power cycled, or the coin door opened and service menu's cycled before the game would boot properly, and it slowly became more and more frequent until the game stopped booting at all. At this point when the game was turned on, just the GI would flash and that was it. The owner called down to Stern for tech support and was told that it was most likely a bad trace somewhere, but even after having a few different sets of eyeballs look the board over nobody was able to see any apparent damage. So LOTR sat broken for almost another 12 months.
The owner gave the MPU to Warlock at the Ottawa show to transport back to me (thanks Scott), in hopes that I could get this repaired by Thanksgiving weekend. The owner would be down in the GTA area visiting family and could pick the MPU up while he was in town. After my own visual inspection I too did not see anything obvious that would indicate an issue, so I pulled up the schematics from Stern's website and sat down with my DMM and began to "ring out" and confirm every single trace between the CPU, the game ROM and RAM chips. All three of these are connected to each other and located DIRECTLY under the original battery holder! Low and behold, I ended up finding one trace between the CPU and the ROM & RAM chip that had gone open. (the trace between the ROM & RAM was fine) Now I wanted to find out WHERE it had gone open.
After looking at this particular trace between the CPU and the ROM I found that it started out on the top of the MPU (component side) but before getting to the ROM it travels through a via to the bottom (solder) side of the PCB. A via is basically a small hole in the PCB, and if you look at the first pic you can see a number of them below where the battery holder was and to the upper right of the CPU chip, they look like pin heads in the PCB as these ones got filled with solder during the mfg process. (some have discoloured from the acid) What happened was acid had leaked over this via, and coincidentally when it was washed with the 50/50 water & vinegar solution some of it got trapped inside the via. (they do not always fill up with solder) I know this because when probing this via with my DMM a tiny bit of water and vinegar actually leaked out! (It smelled of vinegar) Now for those that don't know, vinegar can also be harmful to your PCB over time as it's acidic, and is the reason we dilute it when neutralizing battery acid. What the owner failed to do after washing with this solution was to then wash the PCB in 99% isopropyl alcohol! (make sure it's 99%, as the 70% has too much water in it) This is important as the alcohol disperses any left over (trapped) water/vinegar from the PCB, and then quickly evaporates. So even though the original battery acid was neutralized, the trapped vinegar slowly ate away at the via causing the trace to go open.
Once all other traces were verified good, it was simply a matter of repairing the open trace with a small jumper wire shown in the following pic.
I then took the MPU to a local collectors house to test (as I do not own any new Sterns at the moment) to confirm my repair.
The board was picked up on Sunday, and hopefully another happy customer.
(I'm still waiting to hear from the owner)
D
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