U5000 resistor glowing bright red and no neck glow

kevindg86

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Have a u5000 that worked, picture was a bit jumpy but worked. All of a sudden no neck glow, odd smell, a resistor r100, circled in picture, glowing red. Any ideas on why?
 

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Something's shorted, test the HOT and see if the center leg is shorted to the metal piece behind it (or to either of the outside legs), also check those big brown mylar capacitors and see if any of them are shorted together (leg to leg on the same capacitor)
 
its a u5000 thats for some reason has been modded to just for one resolution. check all the parts going to the I.C. la7850 to make sure nothing is shorted to that point.
 
its a u5000 thats for some reason has been modded to just for one resolution. check all the parts going to the I.C. la7850 to make sure nothing is shorted to that point.

I thought it was a u5000 but someone told me otherwise but as for the ic nothing that I can see looks like it would cause a short
 
So I went resistor test happy, and these were the worst ones.

R500 on the neck board testing only .3-.5 ohm when it should be 3.3,

R120 test at 91K ohms when it is supposed to be 68K.

R528 at 2.5 when it supposed to be 4.7.

And I found that R760 in the manual says it should be 100 ohm when a lot of places say it supposed to be a 470 ohm and mine is test around 550.

Any of these sound like it could be the culprit?
 
What does the Sticker say under the large white resistor lower left of the photo?
Does it sat 2550 or something else.

Also R760 in ALL of my chassis is a 470 Ohm 1 Watt or was it 2 Watt???
 
Well it is a U5000 chassis. To bad someone butchered it to single rez. but if it was only needed for 1 cab.....
I would follow with this advice. if you can find the post for the "light bulb" test I would start there to verify the power supply is working. And measure B+
Next would be to look again for shorts. that resistor will not glow for no reason.
Has it ever had a cap kit? couldn't hurt to do one if it hasn't. "that will not likely fix this issue though"
If the R760 blows or something odd like that, it is not starting the HV properly, but this is not the case.

If you have NO neck glow AND your smoking a huge resistor like that, Could be a flyback issue, funny the HOT did not blow though.....

These chassis are "challenging" unless it is a easy fix.
 
Idk if I feel comfortable doing the light bulb test, especially since the resistor they said to use is close to exploding. I'll test hot tomorrow, but from whay I can see there are no shorts, is there anything specifically I should look you think? I've done a partial cap kit, basically with whatever extra caps I've had laying around. The only one I wanna replace is the 1500uf/35v cap I just didn't have a suitable replacement on hand. Hot seems fine and tested fine as well. Like I said the whole picture was jumpy when I had neck glow so I feel it had a cap issue before hand but the fact there was no ticking and the fact the fly back seems good that it might be a resistor issue
 
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