(Topic ID: 250683)

WPC no 18vdc on power driver board


By blovesj

5 months ago



Topic Stats

  • 4 posts
  • 3 Pinsiders participating
  • Latest reply 5 months ago by Pin_Guy
  • No one calls this topic a favorite

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#1 5 months ago

Attempted to fix an intermittent reset issue on my STTNG. C5 seemed to have a small bulge so I decided to replace all bridge rectifiers (BR1-5) and capacitors (C2,4,5,6,7,8,11,30) on the power driver board to fix the issue, and safeguard against future failed components. In hindsight, I shouldn't have messed with the components that were still working. After finishing the job, all TPs checked out fine except TP8, which is registering 0.5 Vdc versus 18 Vdc. For troubleshooting, I removed and re-soldered BR1 and C6/7, replaced fuse F114, and verified continuity through the entire 18 Vdc circuit. I'm completely stumped because the regulated 12 Vdc at TP3 is fine. Also, LED6 is working. Only the lamps aren't working (GI and all solenoids, flashers are ok) so TP8 is giving an accurate reading. J101 pins 4 and 7 to GND are measuring 447mV and 435mV (seems reasonable); however, J101 pins 4 and 7 to TP8 start at 0V (if I discharge C6/7) then keep increasing until the multimeter shows an overload. These measurements led me to believe that BR1 wasn't making a proper connection, but continuity checks are ok, and I'm getting 12.1 Vdc out of TP3. What am I overlooking? Thanks!

#2 5 months ago

If you are not careful when de-soldering components you can rip out the through-hole-plates connecting the other side of the board.

Check continuity on each side of the board through the legs of the big caps... pad-to-pad.

Electronics is not my strength but this has bit me before. I had to add a stitch to complete the circuit.
faz

#3 5 months ago

SOLVED: C6 negative top trace wasn't making a connection to C7 negative top trace.

#4 5 months ago
Quoted from blovesj:

C5 seemed to have a small bulge so I decided to replace all bridge rectifiers (BR1-5) and capacitors (C2,4,5,6,7,8,11,30) on the power driver board to fix the issue

I die a little inside everytime I read this

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