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820-3115 backlight fuse smoke

K

Kyle93

Active member
Have a 820-3115 that came in with severe water damage. Cleaned and replaced everything but having difficulty with the backlight fuse. Both pads were beyond bringing back so did scraping in the area to solder replacement fuse and running jumpers on each side of fuse

My problem is with my jumper for PPBUS_G3H point pin 1 of the fuse. When I run a jumper to R5400 which has PPBUS_G3H to the fuse it smokes and the jumper breaks. Have tried several different gage of wire with no luck.

Do I need to run jumper somewhere else with PPBUS_G3H or is something else happening here?
 
K

Kyle93

Active member
Ran jumper to C3880 just to be sure and same issue occurs. Jumper smokes and melts as soon as power is applied.

Board powers on and works besides no backlight
 
J

JohnB8812

New member
This sounds downright awful especially if the pads for the fuse were blown out. Do you have a short on backlight output? Is PPBUS grounded by chance where the fuse use to sit?
 
2informaticos

2informaticos

Administrator
Staff member
If you scratched deep inside the board, possibly got a short with the next copper layer.
Check for short to ground on each pad of F9700.
Same thing check on D9701, w/ and w/o LCD connected.
 
K

Kyle93

Active member
Have 0hm short on pad 1 of F9700 so yes PPBUS pad is grounded.

D9701 not shorted with or without LCD.

What is best thing to do in this situation? Scrap new area for fuse near area possibly and then run jumpers?
 

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J

JohnB8812

New member
First, I would say purposefully remove the PPBUS pad where the fuse use to be and see if the short clears. I would consider soldering the fuse directly to pin 4 of Q9706 and jumping the other pad of the fuse to something like R4260. That way you completely cut out the cluster fuck of what's left of the fuse pads and run your circuit away from the mess.
 
2informaticos

2informaticos

Administrator
Staff member
Cut the trace from pad 1/F9700.
The pad 1 can remain grounded, but you must isolate the rest of the trace.
Then solder the fuse as above mentioned.
 
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