(Topic ID: 234458)

WCS94 blowing fuse F104


By cbdarden

10 months ago



Topic Stats

  • 64 posts
  • 7 Pinsiders participating
  • Latest reply 8 months ago by cbdarden
  • Topic is favorited by 4 Pinsiders

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Q82 R135 D32 Z.jpg
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There are 64 posts in this topic. You are on page 2 of 2.
#51 9 months ago
Quoted from robertmee:

For the time it takes to remove the connector, it's silly not to eliminate that possibility. Troubleshooting 101...minimize possibilities of erroneous readings.

Better to test the diode in the circuit with the coil. You'll end up doing it at the end anyway.

A shorted transistor to ground, still will not affect the coil resistance measurement either. I even jumpered a coil to ground braid last night and the coil resistance measured the same, grounded or not. Worked just as I expected.

#52 9 months ago

cbdarden, are you going to be able to change Q82 or have a friend do it? Can you snap a picture of the part? We can help to locate a replacement part. I'm pretty sure it is not the common part found on the original driver board.

#53 9 months ago
Quoted from PinballManiac40:

Better to test the diode in the circuit with the coil. You'll end up doing it at the end anyway.
A shorted transistor to ground, still will not affect the coil resistance measurement either. I even jumpered a coil to ground braid last night and the coil resistance measured the same, grounded or not. Worked just as I expected.

Who said anything about a shorted transistor affecting measurement? I said shorted diode. A shorted diode directly shunts across the 50V and ground lugs of a coil and you would read 0 resistance. You need to lift the connector to both check the diode (otherwise, the diode test will fail across the resistance of the coil), and you need to lift the connector to test the coil in case the diode is shorted. Two tests, one connector lift.

Especially not sure what you meant by "Better to test the diode in circuit with the coil". You can't do that. You always have to lift one leg of the diode off the coil to test. Since these diodes are on the board, you do that by removing the connector. The low impedance of the coil in parallel with the diode will fail the diode test everytime. Instead of reading .6V one way, you'll read ~.1V both ways.

#54 9 months ago
Quoted from PinballManiac40:

cbdarden, are you going to be able to change Q82 or have a friend do it? Can you snap a picture of the part? We can help to locate a replacement part. I'm pretty sure it is not the common part found on the original driver board.

https://docs.wixstatic.com/ugd/846ba2_6dcb501571a04b578f46eeea2c69d692.pdf

Looks to be a 20N10L

1 week later
#55 9 months ago
Quoted from robertmee:

Then sounds like you found your culprit. There will be a diode on the collector of that transistor (Outside leg)...Should be physically right next to it. With the same connector off the board, check the diode. Should have ~.6V with black lead on banded side, red lead on other side, DVM in diode mode. Should have OL/Open with leads opposite.

R135 is reading .480, which is way lower than the others, is that the culprit?

#56 9 months ago

Best take Q82 out of the circuit first, then measure R135 again. It will show its real value then.
Try also to compare the outputs of the ic. For example Q0 pin2 with Q1 pin5.

Q82 R135 D32 Z.jpg

#57 9 months ago
Quoted from cbdarden:

R135 is reading .480, which is way lower than the others, is that the culprit?

R135 would be a resistor, not a diode. Are you saying you read .48 ohms on that resistor?

#58 9 months ago
Quoted from robertmee:

R135 would be a resistor, not a diode. Are you saying you read .48 ohms on that resistor?

Yes, the diode read normal, that resistor read low. That’s with the board completely out of the machine.

In addition, everything worked as normal with my old board back in the machine (it has other issues, hence the replacement).

#59 9 months ago

Certainly sounds suspect, but I'm surprised...resistors usually fail open, not shorted.

#60 9 months ago

Yeah, I’m scratching my head here. The fact that it plays perfectly with the old board, and blows F104 as soon as the new board is put in is definitely leading me to believe the board is the culprit. Since it’s a new Rottendog board, I’m hoping they stand behind their product and I can get a replacement.

If not, I guess I’ll start replacing parts on this new board.

#61 9 months ago

Update: since the Rottendog board is new and the old board I have isn’t blowing that fuse, I’m sending it to them and they’re taking care of me. Hopefully that’ll be it. I’ll update this thread with what they find.

In the meantime, I’ve got GI to swap out and other minor repairs and cleaning to do until I get a board back.

#62 9 months ago

Good luck...will be interested what they find.

2 weeks later
#63 8 months ago

Got the board back, fixed. Everything worked for awhile, now it’s blowing F104 again. I’m back to square one. It plays fine for awhile, then F104 blows and half the coils stop working.

Back to the drawing board...

1 week later
#64 8 months ago

F104 is still blowing, even with the returned board. I'm now reading a beep to ground with the molex unplugged on Q68 and Q78.

Is it possible the board is touching the metal plate behind in these spots? Should I just start replacing every coil in this circuit? I've already unplugged the knocker after it did it once, now it looks like I have a new problem.

I'm really at a loss here. Guess I'll need to call in someone locally in STL to take a look and maybe I can learn from them.

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