[Elecraft] Protective zener diode failure

[David Olean]

Hello Matt and Julian,
It is D-28, the big fat zener.  I had two K3's running off the same supply. 
I have not had any failures of this type with other gear in the past. I 
think I will put some logging software on the output of the supply and look 
at the results. Both failures happened when I was not there to see it.. I 
have to set the logging program sample rate fast enough to see transients 
though. The recording might look like several miles long on my screen!!
    Acopian makes commercial supplies. This one is linear with a number of 
pass transistors. It seems to be working just fine. Stable wiith great 
regulation. However my nose has wrinkled too. I suspect an internal weird 
problem with the PS.  I will use a DATAQ data logger on it, so I can watch 
the ouitput on the computer at my leisure. I better substitute a big 
resistor rather than the K3 this time.

Dave K1WHS


----- Original Message ----- 
From: "Matt Zilmer" <mzilmer at verizon.net>
To: "David Olean" <k1whs at metrocast.net>
Sent: Sunday, November 22, 2009 3:16 AM
Subject: Re: [Elecraft] Protective zener diode failure


Hi Dave -

Does this zener have a designator on the board?  Just curious.  Looks
like it might be D28.

I haven't had this problem, but heard of one K3 user off list that had
this problem - stated same as yours.  He replaced the device and has
had no further problems of this nature.  From over a year ago.