After following the pinwiki regarding ground row shorts I determined that the MPU was at fault. I just got my replacement board and want to make sure I don't fry that one as well. I have run through the entire machine and have not found any physical shorts, my question is, if I connect the new MPU with 206 and 209 disconnected, then testing the matrix from there, will that be enough to protect my new board from frying? Or is there another trick to try?
Thanks,
JLB
possibly ULN2803 (U20)
These are the steps I followed to diagnose the problem...
Follow these steps to determine if the switch matrix problem is on the CPU or somewhere in the game wiring.
Remove connectors J206/J207, J208/209 and J212 from the bottom of the CPU (J206 and J207 are electronically the same and J208 and J209 are electronically the same).
Clip one lead of a test jumper to pin one of J207 making sure you don't touch any of the nearby pins on J207.
Power the game on, and enter Switch Edge test (you've left J205 on the CPU so the diagnostics switches still work).
Touch the other end of the jumper to pin one on J209, then pin two and so on. You should see (and hear) the CPU indicate that switches #11, #12, #13, etc. are being "made" as you touch the pins of J209. You should *never* see multiple switches being made.
Move the jumper from J207 pin 1 to pin 2. Re-test to every pin on J209, listening for the machine to read every switch as closed. Continue in a similar manner testing each pin of J207 to every pin in J209.
I got a short from pin 3-9 of J206 to every pin of J209 (pins 1 and 2 were fine from 1 to 9 on 209)
Quoted from johnwartjr:You replaced the entire board because the 2803 may be bad?
I am guessing the OP can't do board work yet and/or there is nobody close to him who can.
No offense meant to the OP (really!) but buying new boards when only something small is broken seems to be common now. Lots of people doing this.
OP: Hopefully the issue was on the board, and not off. Otherwise yes, putting the new board on could ruin the 2803 if the issue truly wasn't the 2803.
Quoted from buffaloatx:I got a short from pin 3-9 of J206 to every pin of J209 (pins 1 and 2 were fine from 1 to 9 on 209)
I'm not sure what you mean by a short.
The main thing is to make sure you don't have a high voltage shorted to the switch matrix. With the row and column connectors disconnected and the game on, check the female side of each connector and make sure all pins read zero volts.
Quoted from dsuperbee:No offense meant to the OP (really!) but buying new boards when only something small is broken seems to be common now. Lots of people doing this.
Better than lots of people trashing them when they're not qualified to be soldering circuit boards. I spend 90% of my time on CPU boards fixing traces, pads and through-holes that someone has destroyed and about 10% of my time actually troubleshooting a problem on the board.
Quoted from terryb:I'm not sure what you mean by a short.
The main thing is to make sure you don't have a high voltage shorted to the switch matrix. With the row and column connectors disconnected and the game on, check the female side of each connector and make sure all pins read zero volts.Better than lots of people trashing them when they're not qualified to be soldering circuit boards. I spend 90% of my time on CPU boards fixing traces, pads and through-holes that someone has destroyed and about 10% of my time actually troubleshooting a problem on the board.
I agree, but a lot of folks just buy a board without really knowing if the issue is on or off the board. I did not know how to work on boards originally (like most people) but there was no way I was going to spend the going rate, so I got some junked PC boards and learned. It really is not as hard as it seems, and I truly believe anyone can learn how with time and practice.
I just don't want the OP to plug in his brand new board, and have something let the magic smoke out because the real issue was not on the board to begin with.
Most people aren't willing to spend the time and effort as you did. Most just watch a five minute video on YouTube and think they're an expert.
We're definitely in agreement in regards to clearly identifying the board is the only problem.
Quoted from dsuperbee:I am guessing the OP can't do board work yet and/or there is nobody close to him who can.
No offense meant to the OP (really!) but buying new boards when only something small is broken seems to be common now. Lots of people doing this.
OP: Hopefully the issue was on the board, and not off. Otherwise yes, putting the new board on could ruin the 2803 if the issue truly wasn't the 2803.
None taken(really!) I do not do board work because I have a crappy soldering iron, and mediocre soldering skills at best. I firmly believe that the problem is not on the playfield, I went over that thing with an 85 lumen head lamp and a fine toothed comb! I didn't see anything that would cause a row short, or cause an entire row to trigger closed while testing j206 and j209. Again I followed pinwiki to diagnose the problem. According to the wiki it is most likely a blown U20. (It LOOKS ok, but that doesn't always mean it IS ok) so I bought a new MPU. I am going to ship the "blown" one to K's Arcade to get repaired, unless there is a PinGURU here in Austin that will test and repair it for me.
terryb, I will check the female connectors before I hook them up to the new board to make sure I don't have any rouge high voltage running through the matrix.
As always, thanks for all the insight folks.
I will update as soon as I get results.
JLB
A bent diode that is shorting can cause all sorts of weird issues, and can be a PITA to trouble shoot and find.
Spend the money on a decent iron, get some junk boards, and practice, practice, practice! It really isn't that hard, but one does need to take the time to practice. I will tell you I was super nervous when I did my first board repair, but now I am pretty comfortable with it. (Still haven't done a chip yet, but have done a few BR which are difficult)
I cannot test chips yet either, haven't bought a logic probe yet, but I am at the point I need to pick one up.
Quoted from dsuperbee:A bent diode that is shorting can cause all sorts of weird issues, and can be a PITA to trouble shoot and find.
Spend the money on a decent iron, get some junk boards, and practice, practice, practice! It really isn't that hard, but one does need to take the time to practice. I will tell you I was super nervous when I did my first board repair, but now I am pretty comfortable with it. (Still haven't done a chip yet, but have done a few BR which are difficult)
I cannot test chips yet either, haven't bought a logic probe yet, but I am at the point I need to pick one up.
dsuperbee, I know all about bent diodes, after paying a "professional" to repair my CV I was having reset problems, after spending three hours under the hood, I found several diodes shorted across all three legs of their switches. So after that pain, its one of the first things I look for when strange things start occurring with my pins.
Thanks again.
Quoted from buffaloatx:dsuperbee, I know all about bent diodes, after paying a "professional" to repair my CV I was having reset problems, after spending three hours under the hood, I found several diodes shorted across all three legs of their switches. So after that pain, its one of the first things I look for when strange things start occurring with my pins.
Thanks again.
I had similar things happen. Diode issues are tricky lil bastards! 
CRAP, before I installed the new MPU I powered on the game and tested J206 connector for voltage. Found I had about 15 volts running through 7 and 9, found I had voltage running through all legs of U20, around 13 or so I think. Read about 15 of the almost 1,000 threads on switch matrix/ground row shorts found a few of those nagging problems before this nightmare started, broken ground braid, bent diode, failed 10 opto board. So now I'm back to short hunting, again.
As Homer J Simpson once famously said "Urge to kill rising...."
I hope to have time Friday to tear through it again
You lost me there. Did you test J206 as I described, with the row and column connector removed from the board?
Quoted from terryb:The main thing is to make sure you don't have a high voltage shorted to the switch matrix. With the row and column connectors disconnected and the game on, check the female side of each connector and make sure all pins read zero volts.
As far as U20, about half the pins are going to have 12 volts with low pulses and about half the pins will have 5 volts with low pulses. This will be true whether the connectors are on or off.
To be honest, I think we need to start over with the original problem.
buffaloatx i feel your pain. i've been there and i have about the same (or lack of) skill level as you.
I eventually found the short. it was a lamp socket touching...something after i changed the bulb.
The long road to get it fixed took me via getting to know how to operate simple tools like soldering iron, multimeter and dealing with MAD amusements from abroad 
all very character building
I hope you will get it fixed soon
Quoted from terryb:You lost me there. Did you test J206 as I described, with the row and column connector removed from the board?
As far as U20, about half the pins are going to have 12 volts with low pulses and about half the pins will have 5 volts with low pulses. This will be true whether the connectors are on or off.
To be honest, I think we need to start over with the original problem.
I did, nothing was hooked up to the MPU except J205. J206 female pins 1-6 read no voltage, pin 7 read about 15 volts, pin 8 is KEY, pin 9 read about 15 volts. Male pins on j206 read about 14-15 volts except on pin 2, which read 2.5 volts, unfortunately I don't remember what j209 read at all. I forgot to mention that in my last post. I'm going to recheck for physical shorts from lamp sockets, bent diodes, flash/solenoids shorting to wireforms etc., and any possible metal thingy's loose and causing mischief.
Again all suggestions are always welcome.
Also, Thunderpants... ridiculously great handle. I hope with all of your help, and a LOT of good luck I can update this thread with a positive result.
JLB
Not easy, but follow the wires for pins 7 and 9 through the game looking for a short.
The only other option if you get stuck is to unsolder the wire for pin 7, for example, in the middle of the playfield and then see which half (upper or lower) still has voltage. You could continue cutting the circuit in half until you've narrowed it down.
Visual is better though.
Quoted from terryb:Not easy, but follow the wires for pins 7 and 9 through the game looking for a short.
The only other option if you get stuck is to unsolder the wire for pin 7, for example, in the middle of the playfield and then see which half (upper or lower) still has voltage. You could continue cutting the circuit in half until you've narrowed it down.
Visual is better though.
Blargh.... yeah, not easy OR fun, but if I wanted ease and fun I'd go to the Bahamas and retire I guess. I will begin that process today.
Sorry about the long radio silence here regarding this thread, unfortunately my REAL job got in the way of my other job (namely attempting to repair cracked out pinballs)
Ok, so I finally got around to tracing the two wires that were sending voltage back to the MPU on pin 7 and 9. Green/blue, and green/violet. There were no physical shorts above or below the playfield, and nothing in the matrix was getting voltage at any switches. So, I start the process of tracing the entire harness looking for any bare wires, when I come to the 10 opto board where I find green blue and violet getting 16.5 volts. Disconnect the opto board no more voltage at the pins in the back box. Reconnect the opto board, voltage at the back box. After searching the forums about another problem I ran across a thread somewhere about switch matrix problems and found a bit of advice from LTG about opto boards and the LM339 chip causing problems. Seems like this is my case here as well, which might have resulted in receiving faulty results when testing the matrix with a jumper from 206 to 209.
I'm looking for my spare opto board and will update this thread as resolved as soon as I'm sure that it works and I can play a full game.
Thanks
JLB
Resolution was 1 bad 10 Opto board, and a MPU that had lost its mind, replaced both and we are now back in business. Now for a quick flipper rebuild and I can put this game to bed!
Quoted from buffaloatx:Resolution was 1 bad 10 Opto board, and a MPU that had lost its mind, replaced both and we are now back in business. Now for a quick flipper rebuild and I can put this game to bed!
So are you now going to have the original MPU looked at and repaired????? I'm happy for you in the sense that you have a fully functioning game again but, you still have no idea what the original problem was with the MPU and it's always nice to have a fully functioning backup on hand.
Yes, I am going to have the original board repaired. According to PinWiki and most of Pinside its probably the ULN2803 (U20) chip that failed. I have begun practicing board work on some trashed PCB's so I hope to be able to replace the "bad" chip sometime in the near future, but if I don't feel comfortable after a while I am going to ship it off to a pro before I FUBAR it any further.
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