Walk Me Thru a Qbert Knocker Flow chart

Phetishboy

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I changed the dips, changed the fuse, the knocker is there, and plugged in, still no knocker, never has been since I owned the machine. Pretend I have done nothing and my knocker isn't working. Where do I start and in what order do I start checking things?
 
How about testing the knocker. It could be the coil is bad.

Knocker works off the 30VDC line which also supplies power to the speech/sound board. You may test the power at the knocker plug to see if it is getting there when the coil is supposed to fire.

There are also 2 fuses to check:
F6 on the bottom panel.
F21 on the power supply board

DIP 6 - On for kicker to work.
 
How about testing the knocker. It could be the coil is bad.

Knocker works off the 30VDC line which also supplies power to the speech/sound board. You may test the power at the knocker plug to see if it is getting there when the coil is supposed to fire.

There are also 2 fuses to check:
F6 on the bottom panel.
F21 on the power supply board

DIP 6 - On for kicker to work.

Excellent. You are and always have been the man.
 
If everything else fails, it could be a dead driving transistor on the motherboard.

There are 3 transistors mounted along the top of the board next to the card edge connector -- only 1 of them is used at all (for the knocker). The other two are spare parts. IIRC they were going to be used for coin lockout coils but the game didn't need to prevent coin entry during play so they were never used.

Test the transistor and swap it with one of the other two if it tests bad (or just put in a new one of course).

Also, in my cab, the fuse for the knocker is attached inline with the molex disconnect right next to the knocker. It's screwed onto the back of the coin box beside the knocker.
 
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Phet, I wish I had this problem ! ;)

Thanks again man, that Qbert you found me has a good home.

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As far as the knocker goes:

1) Do a continuity check between the lugs on the coil. if no continuity, either a copper wire has come loose from one of the lugs, or the coil itself is bad. You might have a diode across the lugs that you can pull one side and check for a short, too.

2) Make sure the fuse is good.

3) Make sure the wiring is good to the board.

4) Find the drive transistor. Short the center tab to ground for just a second. If the coil is good, the transistor is good, and the power is good, the coil will fire. That also tells you the wiring from the transistor to the coil is fine and the problem lies in the signal from the CPU to the drive transistor. If it won't fire, try replacing the transistor first, then the coil...
 
If you have sound you should have power for the knocker. Check for 30v at the fuse next to the knocker itself or at the coil. You should have +30v at the knocker coil at all times. The knocker is triggered by closing the ground loop for the coil through the transistor on the board. Bench test the knocker assy with a 12v power supply to see if your coil is good. Its not uncommon for the transistor to go bad. If you dont have a new one you can steal one of the other ones off the board. There is one thats for the coin meter that can be robbed.
 
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