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[TenTec] Model 963 25A Power Supply 'burning smell' problem

To: tentec@contesting.com
Subject: [TenTec] Model 963 25A Power Supply 'burning smell' problem
From: Jerry Volpe <kg6tt@arrl.net>
Reply-to: kg6tt@arrl.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 15 Nov 2007 10:38:37 -0800
List-post: <mailto:tentec@contesting.com>
Anyone else experience over-heat damage to the the fuse area on the 963's power supply's circuit board? If so, what did you trace the over-current problem too? In my case it appears that the mini-glass fuses are getting too hot and oozing a reside out one end which seems to be contaminating the physical connection of the fuse at that end and the circuit board clip.... thus inserting some resistance where it shouldn't be. This increase in resistance is creating a current 'hot spot' where the clip is soldered to the circuit board and that area is beginning to literally burn. The power supply is about two years old.

About two months ago I noticed a bad 'burning' smell in the shack for the first time. Took a few moments but the smell was traced to my 963 power supply running my Orion 565. Power output voltage was correct, nevertheless I turned it off immediately and did a visual inspection. Inside I found the circuit board had a small chard area on one side of the circuit-board mounted fuse clip (as described above). I also noted a reside around that end of the glass fuse. There were no other signs of overheating on any other components or on any other part of the circuit board.

I replaced the fuse with a new 10a, 220v fuse and cleaned the fuse holder... checked the solder connections.... reassembled. All was good till this morning. Of course I was getting ready to 'chase' a new one and that familiar smell was in the air. Turned the power supply off and did another internal inspection. Found the new fuse 'leaking' on the same end of the fuse clips and that charred area a bit larger this time. I drilled the back panel and mounted an appropriately sized screw-type fuse holder. I removed the old clips from the board and attached #12 stranded/insulated wires between the circuit board and the new fuse holder..... replaced the fuse. At the moment all is well. However, I did purchase an Astron RS-35M to replace the 963 until I can figure this one out.

Thoughts?

73,
Jerry, KG6TT

--
Ralph Jerald "Jerry" Volpe
Amateur Radio Operator KG6TT
FISTS 12304
http://kg6tt.tomorrowsweb.com
788 Chestnut Drive
Fairfield, CA 94533

kg6tt@arrl.net

510 325-7724
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