This topic was started as a private message. Below is the start of private message.
Hi Grumpy, after working with you on my high speed, i was hoping you could help me gain some insight with another issue i wanted to take care of.
Im not sure if youhave the time, but just incase, here is whats going on:
A few months ago, i bought a WPC-S ROADSHOW.
1 of the solenoids #11 “TEDS EYELIDS UP” was not working.
I disassembled ted, the lids up coil was bad so i replaced the coil for the eyelids.
I checked its transistor Q54. I buzzed out the tab to ground, and it buzzed as bad.
I also tested its legs, which also tested bad.
I replaced Q54 reinstalled the board, and it is still energizing SOL 11 when it shouldnt.
Teds head has a plug which i unplugged so i dont burn out the new coil.
I just tested the pre driver Q53 and it seems to be good.
According to my research, there is a chip ttl 74LS374 that could possibly be bad.
I read that i can put my dmm in diode test with the red lead on the ground leg, and the black on the others. They should test .4-.6 except for the power leg.
I was hoping you could help me figure out which chip it is, and which leg is the power leg.
I have a pic of the pinouts for the chip but cant seem to post it in this message.
It looks like 10 is ground, 1 is input control or OE, 11 is clock and 20 is Vcc.
Also i was wondering if there another way to check to see whats causing the issue, or if i should use my new logic probe somehow. Thanks again for your time. Sparky
Hey Sparky, hows things going with you. Here is a tech tip I learned the hard way. Any time you have a shorted driver, you always replace the shorted driver, predriver and diode and also test the coil for the correct ohms. This only cost you an additional .60 cents in parts and will save you lots of time and frustration.
Now on to your problem, U-4 is the LS374 that needs to be tested.
Pin 5 of U-4 turns on Q-53 by going high.
So use your logic probe and see if pin 5 is stuck high, if it is then you will need to replace U-4.
If it is low then you have a broken trace between pin5 and the base of Q-53.
It can also be a bad solder joint on Q-53 or pin 5 of U-4 causing it to seem like a broken trace.
The last thing is if pin 5 is low, then Q-53 can be bad even tho it tested ok.
D-22 should also be replaced as it is the diode for the shorted coil you changed.