Arcade Collecting > Pinball

Solenoids still fire incorrectly... *FIXED*

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gajaman:
Since buying my Space Invaders some of the solenoids have been firing incorrectly.

I know that the problem is not the MPU as I use a new Alltek replacement. I know the problem is not the solenoid driver board as having tried two boards I get exactly the same result with the same solenoids firing when each switch is hit.

I have checked the wiring from the MPU J4 connector and the SDB J4 connector and this is correct in that the connector pins go to the corresponding pins according to the schematics.

I have fired the solenoids manually by grounding the transistors on the SDB and comparing which transistor should fire which solenoid on the schematic and these are all ok.

Tell me if I'm wrong but based on the above I think;

my MPU is not the problem as it is new
the wiring from my new MPU to the SDB has not been miswired
the SDB itself is not the problem as two boards behave exactly the same way
the wiring from the SDB to the coils has not been miswired either

Could it be a problem that the switches are messed up?

To be honest I'm getting pretty stuck now, I thought it was the SDB but I guess not.

Thanks

RichSorr:
This is always one of the most frustrating issues to me. Do they fire incorrectly during diagnostics? If you haven't already check wiring to the switch matrix or for shorts in the playfield. Does it only happen with certain coils?

gajaman:
This one is drivng me mad, but is a good way to learn some new stuff I guess.

The coils fire the same incorrect way in the diagnostic test mode.

I've just been reading the Pinrepair manual and this suggests that a bad solenoid driver board J4 connector/pins or MPU J4 connector/pins could cause firing of the wrong coils. I've ruled out the pins as the MPU is new and both SDBs do the same thing so I guess I should check the connectors.

What I don't know how to do this. I can check continutity between the connectors by sticking one end of my DMM in one connector and the other DMM end in the corresponding hole in the other connector but this won't tell me if the connector is connecting well with the pins on the board?

How can I test if the pin is connecting nicely with the connector?

RichSorr:
I would Ohm out between connectors, see if you have a bad pin. You could also go between the header pins between boards. If theres not a solid connection between the pins it should show. I really am not familiar with the Alltek boards, but you could try resetting the board and making sure all the switches are set correctly. If it is firing wrong in diagnostics I would lean towards MPU or wiring issues to the boards.

gajaman:
Pinball Jim - Thanks, I really don't want to believe that it's the MPU as it has behaved this way since the MPU was brand new. It seems really unlikely that this would have been defective out of the box? I guess I want to try an rule everything else out before exploring this, it just seems so unlikley.

RichSorr - By ohming out you mean testing continuity right? I can check continuity from connector to connector by detatching the connectors, but how can I test if the connections are good with them connected to the board?  Should I connect them but not push them fully home and test on the visible part of the pins on the board? Would this not be likely to read as not connected when it may be when pushed fully home?

Thanks for the help

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