[Hammarlund] SP600 and BBODs

[Wes Bolin]

Thanks for your comments Ken.  I am replacing all of the BBODs, with the last ones being in the RF Deck.  What you say makes good sense,
and I will be looking for a High Voltage capacitor checker in the upcoming flea markets and hamfests.
I have been out of Ham Radio for several years, and am slowly building up my test equipment and parts supply. I completely sold out of
everything except for a 12 volt DC power supply. The bug bit me again, so the SP600 is under restoration. You are absolutely correct about
tossing all of the BBODs away.  I really dislike them because of the time and work involved.  So, someday the radio will work and be
reliable. 
Wes
 

________________________________
 From: Kenneth G. Gordon <kgordon2006 at frontier.com>
To: Wes Bolin <k5apl at yahoo.com>; hammarlund at mailman.qth.net 
Sent: Monday, March 4, 2013 7:21 PM
Subject: Re: [Hammarlund] SP600 and BBODs
  
Wes:

Checking capacitors with a VTVM will not tell you how they operate under full voltage. Your 
VTVM applies maybe (a big "maybe") 1.5 VDC to them to measure their resistance.

I have several "condenser checkers", and capacitor checkers here, all of which apply full 
working voltages to capcitors at voltages up to 600 VDC.

Two of mine are the ancient Heathkit C-3 which I have rebuilt, one is a copy of the Sprague 
TO-5. I don't have a "megger" yet, but plan to build one. They all work very well, and I use 
them religiously. I rely on them, and they have never let me down.

250 V capacitors that test "good" at 25 VDC, show very, very serious leakage at 250 VDC, 
and some even suddenly short out at their "normal" working voltage when tested on any of 
my cap checkers.

I wouldn't trust even ONE of those darned BBODs anywhere!

If you don't have a real cap checker, you can "synthesize" one by  connecting a capacitor that 
you want to test in series with a milliammeter and a variable HV DC supply, then start 
cranking up the voltage.

You can watch the current climb as the voltage goes up.

There are collections of data which show the allowable leakage of any capacitor and you can 
use those if you want to, but if there is more than a microamp or so of leakage in a 250 V 
capacitor, that is way too much..

If it was me, I would simply yank all of those damned things and toss em. I wouldn't bother 
testing them. All of us have had experiences with those BBODs, and all of those experiences 
have been bad.

But its your receiver and you can do what you want to.

Ken W7EKB