[ARC5] BC-454 Caps

[Brad Hernlem]

>From: David Stinson <arc5 at ix.netcom.com>

>Brad Hernlem wrote:
>
>>Please have a look at the capacitor on the right in the following 
>>pictures:
>> >...I am wondering whether this is a stock unit or something else.
>
>This is a stock unit.
>Just a later supplier.

OK, thanks. That what I figured.

>>I removed it to check it and it seems fine but was oozing goo at one time 
>>before I acquired the receiver.
>
>Be sure to check for leakage from terminal to terminal-
>not just to the case ground.
>They're bad about that.

Hmm, I hadn't bothered to check that.

>
>>... that one on the left is one of the electrolytics. I took all three out 
>>to check them. All read considerably higher in capacitance than spec'd 
>>(100% or more)
>
>Leakage fools many cap checkers into showing higher than rated
>values.  Also, +100% to -25% of rated value of electrolytics
>was considered "normal" in the 1940s.

I was using my Wavetek DMM to check the capacitances. It was very close with 
the 3X.22 unit but high with the electrolytics.

I measured leakage by using a 190 VDC power supply, a 200K current limiting 
resistor, a variac for voltage adjustment (to the unregulated power supply) 
and Simpson 260 VOM to measure current.

>
> > but seemed quite leaky.
>>That one, for example, drew about 0.5 mA at 95 VDC across it.
>
>Is that steady after leaving it on for a few minutes?

It was trending down very slowly but, yes, it was after about 5 minutes. 
Maybe the caps are reformable but how low should the leakage be to be 
comparable to original specs?

This receiver is a beater so I am not apprehensive to put in new components. 
It will never look like original. I had to bang out a lot of dents and scour 
away a lot of pimples but there are many new holes and other changes.

What do you think of using doubled up 0.027 uF X7R ceramic 1000V (one 
thousand volt) 1812 size surface mount caps in place of the numerous .05 uF 
caps? I have the better part of a reel of those caps and it seems like a 
good application.

Brad
KG6IOE

>
>73 Dave S.