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Author Topic: Kepco Power Supply Failure  (Read 179 times)

W0RW

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Kepco Power Supply Failure
« on: December 21, 2022, 08:51:14 AM »

Kepco Power Supply Failure
Old Kepco Power Supplies are the Linear type.
I love them because they don’t cause RFI noise like Switchers do. 
Mine is a Model JQE-25-10 made in 1970, Still running 24 hours a day.
   Last week I decided to put this JQE in service to power my Video camera Controller at 12VDC.  I replaced a Switcher with the Kepco. The Video controller has coax input from remote cameras that are around the outside of my house. One video coax cable runs right over one of my vertical antenna radials.
    I spotted a DX guy on 10 MHz and started to call him, when I hear Pop – Pop and saw smoke from behind my operating desk. The video went blank. It took some time to find this problem.
    The Kepco went to 30VDC and popped 2 Aluminum Capacitors (exploded the cans) inside the Controller, right as I keyed my K3s on the air.  The Kepco was not damaged but the RFI from my radials came back into my shack and overcame the regulator in the Kepco. It went out of regulation and smoked my controller. I replaced the capacitors in the video controller but there are still other parts that are blown up.
   The Kepco would come out of regulation (Linearly) in direct proportion to the 10 MHz RFI amplitude.
I moved the Kepco on to a different battery charging job and have not figured out how to fix it yet.
Paul   w0rw
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WA3SKN

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Re: Kepco Power Supply Failure
« Reply #1 on: January 01, 2023, 11:48:23 AM »

Googled and see that supply in the $75---$235 range.
I am not sure just how much to invest in repair with its age.

-Mike.
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AC2EU

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Re: Kepco Power Supply Failure
« Reply #2 on: January 01, 2023, 12:26:27 PM »

It may be repairable for  a reasonable amount if the pass transistors didn't get destroyed. Even so, I don't think 2n3055 or 2n 3773 types are too expensive these days. Just buy from a real distributor -not Ebay.
It is most likely the failure  started on the control board. . Also, some of those oldies used a crowbar device for OV conditions, which is probably also destroyed.
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