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(Topic ID: 260720)

Doctor Who 18V missing at TP8, LED 6 lit

By RocketFromTombs

8 months ago

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  • 4 posts
  • 3 Pinsiders participating
  • Latest reply 8 months ago by RocketFromTombs
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DSC00568 (resized).JPG

#1 8 months ago

I am going through my Doctor Who that has been sitting for some time, and none of the controlled lamps are working. I checked fuse 114 and it's good, and the 18V LED is lit. I checked voltages at the test points, and TP8 shows 0.0 volts. All other voltages appear to be fine. (TP 1=15.4V, TP2=5.0V, TP3=12.2V, TP6=75.2V [a bit high?] and TP7=22.3V.
I have a copy of the WPC Schematic Manual, but it's pretty much impossible to read the power driver board schematic, as it's so small and crowded... I am having difficulty figuring out what is between the LED and the test point to see what to check.
Any pointers on what I should be looking for?

#2 8 months ago

Has C7 been replaced? I suspect the through hole of the positive lead has been pulled if it has been. That's where the trace from the positive lead of the bridge rectifier crosses from the back of the board to the front of the board. LED6 is placed before C7. TP8 is placed after C7.

#3 8 months ago

This might help ... Dashed lines are tracks on the topside of the board.

DSC00568 (resized).JPG
#4 8 months ago

Yep, I am pretty sure that was among the caps I replaced a few months ago. I will check that out when I get back to it (hopefully tomorrow evening).

And thanks for the photo, PinGuy! That will help too!


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