[R-390] Capacitor tester...

[David Wise]

I'd add that they should be checked when hot.  Leakage goes
up fast with increasing temperature.  It may look okay cold.

After I got my 390A, I decided to replace all of the Prokars
(Brown Beauties) that were (a) highly charged, or (b) at
high-impedance points.  I left the cathode bypasses alone.
Just for fun, I hooked the IF deck to a current-limited power
supply (B+ only), put it in the oven on low, and left it overnight.
Next morning I found two shorted caps, and I was a believer.

Dave Wise 

>-----Original Message-----
>From: r-390-bounces at mailman.qth.net 
>[mailto:r-390-bounces at mailman.qth.net] On Behalf Of chacuff
>Sent: Tuesday, March 06, 2012 5:59 PM
>To: John Saxon; r-390 at mailman.qth.net
>Subject: Re: [R-390] Capacitor tester...
>
>Hi John and group...
>
>John I'm a firm believer in using a cap analyzer in tube radio 
>work.  The 
>cap really needs to be tested at its rated voltage for leakage 
>current.  I 
>have been using the Sencore products for years.  The LC-53, LC-73 and 
>currently the LC-102.  They work great.  A bit pricey at times 
>but if you 
>wait and watch you can usually pick one up priced right.
>
>It can be as simple as using a megar type device with the 
>crank on the side. 
>Works for fishing too if you don't get caught...:-)
>
>The important part is to check the caps at rated voltage.  I 
>can't say I 
>have ever found a Black Beauty or Brown Beauty that tested 
>good....all had 
>excessive leakage.  As a result I usually do a mass paper cap 
>replacement 
>but that is a personal thing.  Many only replace a few in the 
>radio in key 
>spots like the DC blocking cap that can cook your Mechanical 
>filters in the 
>"A" models and let the rest of the rock on...
>
>Be sure to check out the Pearls of Wisdom documents and the 
>nicely done 
>Y2KR390 manual....(may have that name wrong)  Both are must have 
>resources....
>
>Good luck and drop questions on us anytime...someone will 
>always know the 
>answer!
>
>Cecil Acuff
>K5DL