[K3PZN-List] High Voltage Capacitor Explodes - Fire and Smoke

[K3MTT]

Curt
What is the normal operating voltage? Hopefully
today's caps are at least the same quality if not
better than the originals.
Frank K3MTT 

-----Original Message-----
From: k3pzn-list-bounces at mailman.qth.net
[mailto:k3pzn-list-bounces at mailman.qth.net] On
Behalf Of Curt Milton
Sent: Monday, August 21, 2006 1:09 PM
To: Carroll County Amateur Radio Club;
johnpking at comcast.net
Subject: [K3PZN-List] High Voltage Capacitor
Explodes - Fire and Smoke

This is in the category of "have you experienced
this"
and "what should i do now!" Clearly this is a
hobby of adventure even if your operating rarely
leaves your own shack ... 

Last winter I rebuilt the power supply section of
my HW16.  I got some modern caps that were checked
out on an Eico Cap Tester that evaluates leakage
and capacitance under operating voltage.  Rig had
maybe 100 hours on it, or not much below that.
But hadn't been used since early Spring.  

Picture this, XYL reading on family room sofa
while i am sitting a about 5 feet away operating
... after nice QSO to a CT1 on 40m, i shift to 80m
for a CW ragchew.  After 10-15 minutes of QSO i
see no plate current, smell smoke .... i should
have turned off rig but i didnt.  i stuck my head
to back of rig to see what is happening (with key
up ...) - BANG ... one of a pair of 450 volt, 47
uF caps explodes and the paper inside catches
fire!  These caps are used in a voltage doubler
that feeds the final tube, and are equivalent to
the original caps. Very dramatic to say the least
-- singed lid of rig and took a couple hours to
air
out the house.   Glad its not my only rig!  

Since I used the rig a bunch, i likely have
everything wired ok.  I do have ONE identical
replacement cap. 
Maybe after a check-up we'll replace the exploded
cap.
 I hope the transformer survived otherwise the rig
is gone .... suggestions appreciated as this sits
near by workbench for a while.  Maybe this cap
didn't have what it takes, or this cap style won't
survive this application!  

Stay tuned to see if this is the end to my
nostalgia experience!  

73 (especially to those brave enough to have tubes
glowing in their shack)

curt


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