[Heathkit] HP23A trouble

[Carl]

Unless the diodes were mismarked or reversed they should work fine. OTOH, I 
only use 1N5408's for just about everything due to their battleship surge 
ratings and never had a failure. They are certainly cheap enough.

Id start by testing the xfmr with nothing attached to make sure there is no 
damage. Then proceed with caution.

Carl
KM1H





----- Original Message ----- 
From: "Dick KF4NS" <kf4nsradio at verizon.net>
To: <heathkit at mailman.qth.net>
Sent: Friday, October 23, 2009 2:04 PM
Subject: [Heathkit] HP23A trouble


>I recently replaced the diodes with 1N4007's and all was
> fine......until yesterday. I fired it up with no load to record the
> voltages and heard a loud pop. The breaker was tripped so far that it
> reversed the spring contacts so would not reset. I opened it up and
> popped the contacts back to the opposite position and tried again. I
> did the usual visual inspection and the "initial tests" before trying
> again. It tripped again so did my diagnostics and found all the new
> diodes shorted.
>
> I realize that 1N4007's are rated at 1000V PRV but only at 1A. The
> breaker is rated at 2.92A. Is there a preferred sub for the original
> Heathkit diodes? The 125mfd caps are testing ok except C3 at 159mfd
> and C4 is 115mfd. None are shorted.
>
> Have not tested the xfmr yet (I need some bravery liquid before I do
> that, hi,hi). The breaker will be replaced with a slo-blow 3A ceramic
> fuse and should be ok along with an ICL in the power lead.
>
> By the way, anybody have 4 100K 2W to sell me? The existing 10pct.ones
> are all out of tolerance.
>
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
>
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