[Elecraft] Power Supply Question

[Dan Barker]

Diode.

Dan

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net]On Behalf Of G3VVT at aol.com
Sent: Monday, December 12, 2005 8:59 PM
To: k6dgw at foothill.net; elecraft at mailman.qth.net
Subject: Re: [Elecraft] Power Supply Question


Hi Fred,

Your PSU has probably suffered the same fate as our local 70cm repeater PSU
did when we floated a battery across the output for emergencies. When the
PSU
was switched off it blew the DC fuse on the output of the PSU.

The reason is the battery is capable of feeding enough power back into the
PSU to exceed the current rating and rupture the output fuse which normally
protects the PSU. The solution in our case was to fit a relay on the PSU DC
output with it's coil powered from the AC supply. When the AC supply fails,
the
DC output link is cut off from the PSU.

Not all PSU suffer this problem as we never had a problem with the 2m
repeater with floating a large gel cell across that, but yours apparently
did!

Regards,
Bob, G3VVT
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