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WPC 89 Power driver board problem

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pinnie39:
Hi.
Im having problems with my WPC 89 driver board
It had blown a ramp down coil, Q32 etc...
I have replaced all the associated parts, Tip 102 transistor and the smaller one, diode, resistors, logic chip ls 374 etc...
Several times but it keeps locking on and not letting go.
Put another board in and it works fine so its definately driver board, not playfield short etc.. or cpu board.
Is there anything else left?
I have checked and double checked all connections.
Help appreciated
Thanks

wiredoug:
At the risk of the obvious .. you have replaced the coil right?

pinnie39:
Yes. Everything works with another board.

johnwartjr:
How are your repair skills?

Do you have a multimeter? Do you have a logic probe? A schematic?

Do you know how to use them? Can you look at a datasheet for an IC, and understand how it works?

There's something else that's causing the 374 to engage the transistor, most likely.

Using the logic probe, you could check the state of the IC, see if the leg connected to your predriver is in the wrong state, look at the input leg of the 374 and verify whether or not the leg is in the correct state, and trace it back through the board. Or, something from that solenoid is somehow backfeeding voltage back to the driver board. That's a possibility, too. You could check the transistor with the logic probe, with the playfield solenoid connector unplugged, and then with it plugged in.. or, check the connector for voltage while it's unplugged from the driver board.

It'd be tedious.. you'd learn something.. but a lot of people just prefer to send the board out.

There's no harm in making either decision - just comes down to comfort level, amount of time, having the correct tools, etc.

pinnies4me:
John's right, really worth considering sending to be fixed, board level work is not for everyone (I just don't try anymore, beyond me). I have had boards repaired by Beaky before - excellent work and great prices - http://aussiepinball.com/index.php?topic=6827.0

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