Pinbot
Williams, 1986Just picked of my first machine a couple of weeks ago. It is a PinBot. Had the left pop bumper not working, found someone had installed the diode on backwards, repaired that with a new diode installed correctly. Schematics shows the driver to be Q47.
The coil now stays locked on when powered up. I have read it here to check both driver and pre driver with this issue.
I tested Q47 and get .6v on both N legs.
My newbie question is, I don't know the pre driver.
Appreciate any help/guidance.
Q47 is not the driver for the bumpers.
The left jet bumper driver is Q73 (solenoid table pg 27 of the manual)
The predriver for Q73 is Q72.
2N4401 (pre-drivers): Put the red lead of your DMM on the center lead of the transistor (note this transistor doesn't have a metal tab). Put the black lead of your DMM on each of the two outside legs of the transistor. You should get a reading of .4 to .6 volts. Any other value, and the transistor is bad and will need to be replaced.
Check Q73 & Q72
Q73 check out .53 on one leg and .00 on the other.
Q72 check out .56 on one leg and .24 on the other.
I checked the other drives in that group (Q69, Q71, Q75, Q77 & Q79) and they checked the same. (.53 & .00)
I checked the other predrivers in the group (Q68, Q70, Q74, Q76 & Q78) and they checked the same (.56 & .24)
Any suggestions or ideas?
I should have asked this before, have you made certain that the pop activation switch is not shorted or stuck on? There are 2 switches for these early Sys 11s - a pop activation switch and a scoring switch that reports to the CPU. To rule out the switch, pull connector 1J18 from the CPU board. Just need to check this before moving onward.
If there is no problem with the switch we would want to check signal flow next.
Okay, I pull connector 1J18 from the CPU Board. Left Bumper still stays on.
I also took and jumped the ground from the Top Bumper, which works, and the Left Bumper didn't come on (after removing the ground from the the Left Bumper).
The Lower Bumper, which I have out of the machine, and told by the previous owner it also stayed lock on, when I jumped the ground from it to the Left Bumper, it also stayed lock on.
So, it looks like the top bumper works, the lower and left are getting a bad signal from the ground.
I'm confused as why the Q79 (top), Q75 (lower) and the Q73 (left) all read the same. .53 on one leg and .00 on the other, but the top bumper works!
Any suggestions?
With the connectors pulled off, what are the signals when you measure on the 7402 IC? It can be measured by comparing 5V/0V signals. Compare the "broken" circuit with the "good" one.
These IC's sometimes fail as well.
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Elizabeth City, NC