K7000 P538 Chassis blowing voltage regulator (IC4)?!

sslakkerr

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K7000 P538 Chassis blowing voltage regulator (IC4)?!

K7000 P538 older chassis with STR3130 IC4

I capped the chassis and hooked it up to find the vertical size was huge and could not adjust to fit the screen properly. Read a bunch of technical bulletins and threads that pointed to the voltage reg. being the problem. This board has the 3130 IC. So I order a couple from br and installed one. Fired it up and it pop! so I quickly shut it down. I removed the chassis and upon inspection found burn marks at the mounting screws of the 3130 chip. The only change to the board was replacing the 3130 chip with a like chip. Any ideas what the deal is?

I also looked over the rest of the board and nothing is jumping out at me. Checked the bridge diodes and they all read okay. I did use Arctic Silver as the thermal compound, which I use all the time for CPU heatsinks.. Was this a no no?

Pics attached. The original was 04A, replacement was 04C in pic.
 

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Did you install the plastic insulator?

Did you check the other components in tht area to ensure they aren't shorted and causing a problem?
 
ya the insulator is there. it's in the pic but hard to see with the thermal compound over it. Now it has burn holes through it so I need to replace it..what's a replacement for that? I checked the resistors and the diodes upstream of the IC..haven't checked the mega cap. Could downstream components cause it to fail like this? Are there some other key components to check? I assumed the diodes were the biggies..
 
The large ceramic resistor parallels the VR so that is a good place to start. Also C55, C56, and C57 are nearby in the circuit as well as R84, R85, and R86.

This monitor requires isloated power, you didn't plug it directly into mains power did you?

I recently saw a K7000 with a burned up vertical hold pot that also appears to have blown the VR, I didn't investigate if they were related, but it is somewhere to start.

How long did it take to blow? Have you checked the input power from your rig, it not only needs to be isolated but it needs to be close to 120vac as well.
 
and arctic silver has some silver in it and is slightly conductive. don't use it unless it says non conductive on the tube.

Check C36 and C38, diodes 19-24. see if any are shorted.
also your H.O.T, and D18.
...

Peace
Buffett
 
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