WGK7000 R103 burns out

Arm123

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I have a 25" chassis here that keeps blowing R103 (2.7ohm / 7w). I have already replaced it once and it blew again.

Since then, I have replaced the HOT, recapped and a new FB. Im still looking into the cause of the burning resistor. Still have to check D19 - D24.

I can only find 2.7ohm / 10w resistors to replace it with. Is that ok to do ?
 
Higher wattage is fine. You should check the VR and those diodes first, as well as some of those caps and other parts around the VR. If one is shorted to ground it would pull too much current through R103 and cause it to burn up. Is the fuse blowing?
 
i have a chassis or two like that that i simply said f-it and bought another chassis to fix up.

If its not something obious, you will smoke alot of those before you find the issue if you ever do.
 
tested: c59 c60 c61 d19 d20 d21 d22 d23 d24...all good

tested ic4 and found a short between pins 3 and 4... replacing with NTE1777

gonna have a look at bthe caps diodes in that area as per your suggestion
 
c37 bad replaced
c38 bad replaced

d15 good
d16 good
d17 good
d18 good

anything else i should look at before i fire it up?
 
Check the fuse again. You almost never get a bad C38 or VR without blowing the fuse...
 
fuse is good... isnt that odd ? It hasnt blown once yet. Perhaps its the wrong value ? Ill have to check again tomorrow, before i test it.

Thanks man
 
Alright... making progress.

Powers up and displays a shrunk / folded over image at the top and bottom. Picture is only good in the middle.

I would lean towards it being a cap problem, if i hadnt already recapped it. I also replaced IC2 and IC3.

When trying to adjust the verical size pot... it does nothing until a certain point then a touch more and it expands to fill the whole screen but it looks zoomed in on the middle portion of the screen. To the point where the individual lines of raster have large spaces between them.

I guess i need to look around and see if anyone else has had a similar issue. Any ideas ?
 
you sure the pot isnt cracked or just worn out? Thts ptoly not it, but always worth a second check just to make sure.


weired raster lines, sounds like the monitor cant draw the picture properly, something freaky is going on.
 
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I just noticed on another k7000 25" chassis, there is no c37 and there is a bridge where d15 should be.. wtf ?
 
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