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(Topic ID: 272079)

Missing 20v - Creature From The Black Lagoon


By at1105

3 months ago



Topic Stats

  • 8 posts
  • 3 Pinsiders participating
  • Latest reply 3 months ago by Ronkz650
  • No one calls this topic a favorite

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#1 3 months ago

I recently got a CFTBL and noticed the flashers weren’t working. It has a Rotten dog driver board and cpu board. Opened the head and noticed the 20v LED isn’t lit. I have checked the fuses and they are all good. The interlock switch is good but strangely doesn’t have any effect when opened. The voltages at J102 connector are

When plugged in
Pins 1&2 - <1 VAC
Pins 3&4 - 16.6 VAC

When NOT plugged in
Pins 1&2 - 11 VAC
Pins 3&4 - 5 VAC

Not sure where to go from here. Any ideas?

#2 3 months ago

Plug J102 back in.
Power on.
Measure AC voltage between J102 pins 1 and 4.
It should be about 18VAC.
Report back.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#3 3 months ago
Quoted from ChrisHibler:

Plug J102 back in.
Power on.
Measure AC voltage between J102 pins 1 and 4.
It should be about 18VAC.
Report back.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Between pins 1 & 4 measures 17 VAC

#4 3 months ago
Quoted from at1105:

Between pins 1 & 4 measures 17 VAC

That's good. That is what it should be.
Remove and "buzz" F111 to ensure that fuse is good.
After that, next step is to test BR4.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#5 3 months ago
Quoted from ChrisHibler:

That's good. That is what it should be.
Remove and "buzz" F111 to ensure that fuse is good.
After that, next step is to test BR4.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Fuse tested good. I couldn’t locate BR4. This Rottendog board doesn’t seem to have one.

#6 3 months ago

Oh. Forgot it was a RD.
Follow the trace from F111 to a pair of large diodes. Those two diodes will also connect to two other diodes. Test all four of those diodes.

Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

#7 3 months ago
Quoted from ChrisHibler:

Oh. Forgot it was a RD.
Follow the trace from F111 to a pair of large diodes. Those two diodes will also connect to two other diodes. Test all four of those diodes.

Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

It’s fixed! I checked those diodes and they tested good so I went back and pulled the fuse again and it tested bad this time! Strangely it tested good the first time. Not sure how. So I replaced the fuse and the 20v is back.

Thanks for your help!

#8 3 months ago

Glad it's fixed. Best way to check fuses is to simply check volts on both ends. Of course both ends need the same voltage, whether it be AC or DC. No need to ever pull a fuse out to check it. Check between J102 pin one and the fuse would have revealed you had 17vac on one end, 0vac on the other end and for sure that means a bad fuse.

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