Williams Road Kings locked coils - Fixed

OP
Quoted from Yuyito:
I disconnected the wire plug (1P19) going to the MPU and it still doing the same thing. Would this eliminate the MPU as the cause of the problem?

If you are sure that 1J19 is disconnected and you are still locking 3 coils, then 3 wires somewhere between the coils and this connector are shorted to ground somewhere. Hard to short 3 wires to ground at the same time unless the harness is caught under a sharp metal object. Follow this connector (1J19)with 8 wires down to the p/f looking for something out of the ordinary.

#3 6 years ago

JEM

Yuyito

Pinside member

Hello Grumpy, I appreciate the reply. I double check and follow the wires and nothing looks out of place. I'm completely stump on this one.

#4 6 years ago

DEC

GRUMPY

Pinside member

These all have U-45 in common. But this shouldn't matter if you have disconnected 1J19.

#5 6 years ago

JEM

Yuyito

Pinside member

Ok. I goofed. I disconnected 1P18 (special solenoid switches) instead of 1J19 (special solenoids). Once I disconnected 1P19 the problem is gone. The problem must be in the MPU like I originally thought. I guess I should test the transistors and the U-45. anything else I should test on the MPU?

#6 6 years ago

DEC

GRUMPY

Pinside member

OP
Quoted from Yuyito:
I disconnected 1P18 (special solenoid switches) instead of 1J19

This is what I was thinking.

OP
Quoted from Yuyito:
I should test the transistors and the U-45. anything else I should test on the MPU?

You should buy a logic probe for testing.

#7 6 years ago

JEM

Yuyito

Pinside member

I just ordered one on amazon. Thanks for your help.

#8 6 years ago

DEC

GRUMPY

Pinside member

Let me know when you get it.

#9 6 years ago

JEM

Yuyito

Pinside member

I got an Elenco LP-560 logic probe. Where should I start testing?

#10 6 years ago

DEC

GRUMPY

Pinside member

With 1J19 disconnected, hook up your logic probe to the test points on the cpu board. Red lead to the 5 volt test point and the black lead to the ground test point. Set logic probe to TLL setting and turn on game power. Check your logic probe by touching the 5 volt test point with the tip, should show a high. Now check the ground test point, it should show a low. Now locate U-45 NOR chip. Check pins 2, 5, 9 and 12, all should be high. Now check pins 3, 6 , 8 and 11, all should be high. Now check pins 1, 4, 10 and 13, all should be low. Then start a game and retest pins 3, 6, 8, and 11 they all should now be low now. Let me know what you find.

#11 6 years ago

JEM

Yuyito

Pinside member

Ok, after testing. 2, 5, 9, and 12 are high. 3, 6, 8 and 11 are high. 1, 4, 10 and 13 no reading. After game start 3, 6, 8 and 11 are low now.

#12 6 years ago

DEC

GRUMPY

Pinside member

No reading will turn on the predriver. Sounds like you need to replace U-45.

#13 6 years ago

JEM

Yuyito

Pinside member

I got some 7407 on order from Mouser Electronics. Thank you for your help.

#14 6 years ago

DEC

GRUMPY

Pinside member

Terry B has a good guide, soldering for beginners. It a good read for everyone.

#15 6 years ago

JEM

Yuyito

Pinside member

I replace U-45 with a new 7407 and the problem continues. I didn't have to solder it, somebody already put a socket there.

#16 6 years ago

DEC

GRUMPY

Pinside member

If the coils locked on to long or too many times the predivers, drivers and coil diodes may have been damaged also. Why don't you cut the base lead of a predriver (Q-72) and retest the Nor chip output at pin 1. If pin 1 works correctly now, then the predriver and driver were loading down the output of the chip.

#17 6 years ago

JEM

Yuyito

Pinside member

Ok, after cutting base lead on Q-72. 2, 5, 9, and 12 are high. 3, 6, 8 and 11 are high. 1 is high. 4, 10 and 13 no reading. After game start 3, 6, 8 and 11 are low now.

#18 6 years ago

DEC

GRUMPY

Pinside member

OP
Quoted from Yuyito:
I replace U-45 with a new 7407 and the problem continues.

Are you sure about the 7407? This chip should be a 7402.

#19 6 years ago

JEM

Yuyito

Pinside member

Yes. You are right the U-45 is a 7402. The U-49 is the 7407.

#20 6 years ago

JEM

Yuyito

Pinside member

I got some 7402's and 7407's that I ordered from Mouser Electronics. Same results with a 7402 on U-45.

#21 6 years ago

DEC

GRUMPY

Pinside member

Upon power up pin 2,3 of U-45 are high and pin 1 is also high. Then these are not NOR chips. They must be OR or AND chips. They maybe mislabeled.

#22 6 years ago

JEM

Yuyito

Pinside member

Right again. I got the right stuff on order this time. I'll tackle this next week. Thanks.

#23 6 years ago

JEM

Yuyito

Pinside member

Fixed the problem. Turn out to be a bad 7402 on U-45. Thank you for your help and happy holidays.

#24 6 years ago

DEC

GRUMPY

Pinside member