Theatre of Magic
Bally, 1995Hey guys - Column 6 of my TOM switch matrix isn't working...this takes out the slings, top lanes, and bumpers. Here's my guess to what may have caused it: I was switching out GI bulbs for LEDs...I was doing this from under the playfield by removing sockets (with the power on...yes, smack me). It's likely one of the sockets grazed a switch. So - if that's what indeed happened, what is it likely that I damaged? Switch diode or something on the CPU?
Quoted from LTG:You took out U20 on your CPU.
LTg : )
BLARGH! Well, I think I have some spares around here... 
Though - I did just test the diode on the most likey spot where the grazing happened...and it was dead...so - fingers crossed, changing diode is cheap and easy.
EDIT:
YAY, U20 is socketed! I had a spare chip, put it in...all is working now.
Thanks Lloyd!
Are U20's always socketed or did i just get lucky?
Thanks for this thread, I have the exact same problem from doing the same thing.
Now.... what is a u20?
Quoted from Rarehero:Are U20's always socketed or did i just get lucky?
On WPC-S and WPC-95 they are socketed by factory since they go out so much / so easily. On WPC they were not so if you see one socketed, it means that it was already replaced.
Quoted from markmon:On WPC-S and WPC-95 they are socketed by factory since they go out so much / so easily. On WPC they were not so if you see one socketed, it means that it was already replaced.
Sweeeeet...yay, I got lucky!
Hey,
Just a quick bit of advice. I had the same issue on my TZ; had to replace the ULN2708A (I think that's the chip), and it wasn't socketed. If you're in there on an older game and changing the chip out anyhow, throw a socket in there. You have to do the soldering anyhow, and makes it easier if it happens again...
Luke
Quoted from lukerp:Hey,
Just a quick bit of advice. I had the same issue on my TZ; had to replace the ULN2708A (I think that's the chip), and it wasn't socketed. If you're in there on an older game and changing the chip out anyhow, throw a socket in there. You have to do the soldering anyhow, and makes it easier if it happens again...
Luke
Yup, I had a bad chip on a battery-leak damaged board. Definitely worth replacing it with a socket.
BTW - can anyone recommend a good cutter for those "close to the board" chips and such? I had one that was just OK...but it broke anyway. Would be nice to have the right tool handy for future repairs.
Quoted from Rarehero:...
BTW - can anyone recommend a good cutter for those "close to the board" chips and such? I had one that was just OK...but it broke anyway. Would be nice to have the right tool handy for future repairs.
Look for a cutter like this:
ebay.com link: Wiha 56818 Precision Electronic Diagonal Cutters Wide Pointed Head
There are also others to find, that are a bit cheaper, but this one is good.
- Ingo
I have seen a lots of WPC89 games with sockets at U20. I am pretty sure this appeared in some games prior to WPC-S from the factory, but not all.
eBay link doesn't work. Here's one from Hakko. You want the blades to be very narrow so they will fit between the pins on an IC.
http://www.amazon.com/Hakko-CHP170-Micro-Cutter-16AWG/dp/B0000WT6FI/ref=sr_1_3
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