[Hammarlund] SP600 and BBODs

[Wes Bolin]

Others have remarked that the modern capacitors are so much better than the oldies. When I restored Collins S-lines and A series radios, the first
thing advised was to replace the 'green' tubulars and paper capacitors. It made a great difference in their performance, so all of the BBODs are
going to be replaced in my SP600.  Thanks for your comments, Glen.
Wes
 

________________________________
 From: Glen Zook <gzook at yahoo.com>
To: Ken Gordon <kgordon2006 at frontier.com>; Wes Bolin <k5apl at yahoo.com>; "hammarlund at mailman.qth.net" <hammarlund at mailman.qth.net> 
Sent: Monday, March 4, 2013 7:25 PM
Subject: Re: [Hammarlund] SP600 and BBODs
  

Unfortunately, the Black Beauty, as well as quite a number of other paper capacitors, go bad just sitting new, on the shelf!  Of course, the audiophools just "love" the Black Beauty capacitors and pay a premium price for even those that are pretty leaky.

Glen, K9STH


Website: http://k9sth.com


________________________________
 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.