Star Trek
Bally, 1979You're currently viewing posts by Pinsider seeburg220.
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Update: drop target solenoid issue has been fixed. But, it still won't start a game. I checked continuity on the two credit button wires to the MPU and they are good. There are credits showing on the display. I swapped MPU boards out with another working game I have and no change.
Quoted from Quench:Are you measuring 43 volts DC on both lugs of the drop target reset coil?
Found a broken coil wire, so it works now under test mode. Still won't start a game.
Quoted from Quench:Have to ask, but you do have credits on the machine?
Does the start button respond in switch test? What about the other cabinet/coin door switches in switch test mode?
It does have credits. The coin switches register but the start button doesn't. A few playfield switches do not, either.
I did do a playfield swap on it, so I must have screwed up some wiring. Will go back and study the pictures I took before I swapped it.
Quoted from Quench:The start button cabling connects to MPU J3, while the playfield switches connect to MPU J2.
They share the same switch matrix signals.
Only way one can affect the other is if you have a short. Are you getting any stuck switches reported in switch test mode?
I did have several, but adjusted them and now have none showing, but still no game start. I took detailed photos of the underside before I made the playfield switch, so I'm gonna pull the playfield out and check every connection, every wire. Hopefully, I will find the culprit.
Edit - I did find several playfield switches that aren't registering at all.
Here's the latest:
Top Rollover #22 in manual does not register in switch test mode. It does however, trigger several lamps on the playfield.
Lower Thumper Bumper #38 does not register, but does trigger several different lamps on playfield (different lamps than the ones above).
"A" Rollover at the top #30 does not register. Also, the manual is wrong: It shows B as #30 and A as #31. B is really #31 and A is #30. I verified the before picture on the wiring for this. "A" is not registering. B is registering.
Credit start button does not register.
I need help with the matrix: the line I've highlighted has all of the the switch issues. What's my next step? Find that wire and physically trace it back to the MPU ? Or, should I start removing switches on that line one at a time, to see if it clears up? Troubleshooting is something I could use some expertise with. Thanks all !
20200920_172530 (resized).jpgScreenshot (4) (resized).pngQuoted from Quench:Both the schematics and switch test mode identification tables in the manual show "B" at switch #31 and "A" at switch #30. Where are you seeing this error in the manual?
That row in the switch matrix you highlighted says you have a short circuit to ground on that "I5" switch return signal. It's a Brown-Yellow wire. Carefully inspect the three playfield switches (bottom pop bumper, "A" rollover and top upper rollover button) it's wired to looking for a short to a lamp socket.
Note, the start button is also on that I5 switch return signal which is why it's not working.
Pull out the playfield switch harness connector from J2 at the MPU board.
Can you now start a game? If yes, it tells you the issue is on the playfield.
My manual shows B as switch #30 and A as #31 (see pic below).
I've gone over the 3 playfield switches carefully and see no short issues.
I unplugged J2 at the MPU and it still does not start. (there are 35 credits showing as well).
I checked continuity on the 3 playfield switches, as well as the start button to the mpu connector and all are working.
Totally stumped...
20200921_111638 (resized).jpg20200921_111735 (resized).jpgQuoted from Quench:Ok, this time go into switch test mode and then pull J3 live off the MPU board. Do those 3 playfield switches now work?
Switch #30 (A) is now working, just arbitrarily, all of a sudden.
I pulled J3 live and no change. The upper rollover button and the lower pop bumper do not register in test mode.
Quoted from Quench:Did this happen after you pulled J3?
Presuming you have a genuine factory Bally MPU board, grab a jumper wire and connect one end to test point TP1, touch the other end of the wire on pin 14 of J3. Does it start a game?
If it's a Bally MPU board, can you post some clear high res pictures?
No, it happened before I pulled it.
I have an Alltek MPU board. I swapped it with another known working Alltek and no change.
Quoted from Quench:Actually this looks like your issue. The ground on the G.I lamp was probably shorting to the "A" switch frame that's mechanically connected to the "I5" switch return Brown-Yellow wire.
[quoted image]
I see. So it does make sense ! Thanks again for taking the time to explain this. I really do like learning more about these. Cheers
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New Brighton, PA