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Old 04-20-2013, 10:43 AM
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Zenith6S321 Zenith6S321 is offline
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Join Date: Aug 2010
Location: Charleston, West Virginia
Posts: 303
I wanted to test the power supply rewiring and cap re-stuffing. The power cord was intermittent, the chassis mounted cheater socket removed, and the cheater cord cut and soldered in. So I removed the kludge and replaced the chassis mounted cheater socket. Its now back to factory configuration. I removed all of the fuses expect for the main 4.5A 400VAC supply fuse. I brought the power up on a variac with a dim-bulb while measuring the 400VDC supply rail across the 80uF 450VDC cap. At about 300VDC I saw the dim-bulb flicker brighter, heard a "pfffft" sound from under the chassis and smelled smoke!

I cut power and turned the chassis upside down. After not finding anything really wrong, I brought the power back up and saw the source of the smoke. The phenolic insulator of one of the voltage doubler capacitors had carbonized and was heating/burning/smoking intermitantly. The voltage on that capacitors' case is at 200VDC, so there is 200VDC across the phenloic insulator. I guess that's why I removed that cap from the set so many years ago. So I removed the re-stuffed caps' ground wire from the can ground lug to remove the 200VDC across the carbonized insulator and then wired the re-stuffed caps' ground directly to the other voltage doubler capacitor. Here are some pictures. Its all better now.

Now to start the long process of replacing all the paper caps and out-of-tolerance resistors....
Attached Images
File Type: jpg carbontrack-before.jpg (41.2 KB, 77 views)
File Type: jpg carbontrack-after.jpg (139.0 KB, 65 views)

Last edited by Zenith6S321; 04-20-2013 at 10:50 AM.
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