Junk Yard
Williams, 1996Having issues with Junk Yard, randomly (and rarely) exiting the active game. Sometimes it says "I hate dogs" and goes into a tournament selection mode, other times it will just end the game. Not power resets, but premature termination or interruption of game play. Flaky RAM? Thoughts? Thanks!
New info, game now slam tilts during multiball. Checked switches in column and row of slam tilt switch and all appear to be working properly and afen't triggering other switches. Any more thoughts?
Physically examine every one of those switches.
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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
Replaced all switch diodes in row and column, inspected also. Issue remains.
Was able to simulate the slam tilt in switch test, which is a big step forward!
If 11, 18, and 28 are closed, 21 closes (slam tilt).
Simulated on board using jumpers and diodes and issue is also present.
Where on the board to start?
Check that no diodes are reversed on the switches in those rows/columns. Especially on 11, 18 & 28.
Check that diodes are not loose (solder break) and wiring to switch is not loose in those rows/columns.
Quoted from adalogue:New info, game now slam tilts during multiball. Checked switches in column and row of slam tilt switch and all appear to be working properly and afen't triggering other switches. Any more thoughts?
Quoted from adalogue:Was able to simulate the slam tilt in switch test, which is a big step forward!
If 11, 18, and 28 are closed, 21 closes (slam tilt).
I just repaired a game yesterday with similar issues everything tested good alone, but when 2 specific targets were activated simultaneously it would slam tilt. It was happening because one of the switches was wired wrong.
Quoted from adalogue:Replaced all switch diodes in row and column, inspected also. Issue remains.
Was able to simulate the slam tilt in switch test, which is a big step forward!
If 11, 18, and 28 are closed, 21 closes (slam tilt).
Simulated on board using jumpers and diodes and issue is also present.
Where on the board to start?
You have about nailed it.
Examine switch 18 closely for reversed diode, leads touching, etc. That's where my money is.
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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
Quoted from adalogue:Simulated on board using jumpers and diodes and issue is also present.
Unless I'm missing something, it sounds like you've narrowed it down to a board issue. So just to double check you removed the row and column connectors and jumpered row1 to column1, row 1 to column 8 and row 2 to column 8 (using a diode in all cases) and switch 21 also indicated closed? If that's correct then continue reading.
Next question is if the problem is in the row or column. Check all of the column voltages at the CPU. This is a pulsed signal and if one is locked on, which could be causing your problem, it will have a higher voltage reading (specifically column 2).
You could also close the following switches and see what happens: 16, 17 and 27. If switch 26 also indicates closed you've got a column problem.
To check for a row problem close switches 51, 58 and 68. If 61 shows closed you've got a row problem.
Oh. Wait. When you said "on board", did you mean actually on the MPU board? If so, I missed that.
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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
Yes, unplugged playfield connectors from CPU board and used diodes to turn on 11, 18, and 28. 21 also came on. So I'm confident it's a board issue.
Ok, will check column strobe with the scope. I noticed the 2803 (U20) is socketed, I'm assuming that's not how WPC-95 CPU boards shipped?
Quoted from adalogue:I noticed the 2803 (U20) is socketed, I'm assuming that's not how WPC-95 CPU boards shipped?
Nope. You're in luck. That IS the way they shipped. 
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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
Quoted from adalogue:Ok, will check column strobe with the scope.
Happy to see a man with a scope. That makes it so much easier.
Chris wins.
Columns checked out with scope.
Did some more playfield switch testing and started getting a row 8 GND short. Traced it to the shooter lane switch touching the autolauncher touching the shooter rod (which is grounded). Switch looked a bit rough so replaced it (switch 18) and now everything works 100%.
I am still confused why I was able to reproduce the previous slam tilt error by jumpering the switch pins on the CPU, maybe I had a diode backwards...
Thanks everyone.
Wow. That was a weird one. Good find!
--
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
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Hopkins, MN