[Boatanchors] Heathkit HP-23 bridge rectifier failure

[Revcom Electronics]

HP-23, usually when diodes short, they just go "Grunt!" and
snap, the breaker pops.  The early HP-23 suffered from this
ill.  Using newer higher PRV diodes seems to have cured it.
Breaker is adequate.

Rod
K0EQH

----- Original Message -----
From: "Dick KF4NS" <kf4nsradio at verizon.net>
To: <boatanchors at mailman.qth.net>; <HEATH at LISTSERV.TEMPE.GOV>;
<heathkit at mailman.qth.net>
Cc: "Bob Hardie W5EUQ" <bhardie at wtta.sbgnet.com>
Sent: Saturday, July 21, 2007 2:41 PM
Subject: [Boatanchors] Heathkit HP-23 bridge rectifier failure


> Just had a strange failure in my HP-23A (purchased from a friend last
> year for a spare) while using it with my Heathkit HW-100 on the bench.
> Had been running some tests and making some xmit adjustments and quit
> to go to lunch. Got back and the rig was off. Found the rig and cable
> ok so started checking the PS which would trip with each reset of the
> breaker in the HP-23. No mic was plugged in and vox was not on and rig
> was in recv mode.
>
> Only took a short time to discover that the HV was shorted to ground.
> Suffered an avalanche through the four diodes in the bridge. All
> looked fine, no burns or discoloration. They were all shorted.
>
> This brings up a point. Is the breaker in there adequate? It appears
> not to me. I am so lucky that the xfmr was not destroyed. Has anyone
> replaced the breaker in there with a fuse or built a crowbar circuit
> to improve protection?
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
>
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