[Collins] Re: Orange drops vs the competition

[David Knepper]

Dr. Jerry and all

I did the test of applying 300 volts to the one end of a "black beauty"
capacitor that had been removed from my 75A-4 and then measure the voltage
from the other side.  Guess what they are failed, that is, the leakage was
over 50 volts.

I concur with Dr. Jerry that these caps. need to be removed as a matter of
good preventative maintenance.

Thank you


David, W3ST
Publisher of the Collins Journal
Secretary to the Collins Radio Association
To Join the CRA go to www.collinsra.com
Nets:  3805 Khz, Monday/Wednesdays 8 PM EST and 14250 Khz Saturday, 12 Noon
EST

----- Original Message -----
From: "Gerald" <geraldj at ispwest.com>
To: "David Knepper" <cra at floodcity.net>
Sent: Tuesday, July 12, 2005 12:31 PM
Subject: Re: Orange drops vs the competition


> I specify Vishay Sprague Orange Drops by name (and part number when
> necessary) because:
>
> 1. they are American made, I think.
>
> 2. They are well made.
>
> 3. They have extended foil for lower inductance than ordinary foil/film
> capacitors that have only occasional tabs out of the roll for
> connections.
>
> 4. I've abused them severely and they come away still not leaking. Back
> when they were so new they were giving them away as samples, I had one
> in my pants pocket. It didn't get removed when the pants got washed in
> mom's Maytag square tub washer, then run through the ringers, rinsed and
> wrung again, then dried in a high speed electric dryer. It also didn't
> take on water or get electrically leaky. That's unscientific, but a
> great deal of concentrated abuse.
>
> 5. Some of the imported poly capacitors have come with very thin films
> and leads as thin so they failed from leads breaking off flush with the
> dipped coating.
>
> 6. There's no problem fitting Orange Drops in place of Black Beauties
> because the Orange Drops are smaller. I suppose for appearance, one
> could wish there was something in an axial lead capacitor with a molded
> black case (and there was a line of Black Beauties sold for replacements
> in the 60s that did have a combination of paper and polyester for
> insulation that don't show the leakage of the all paper/oil molded Black
> Beauties, but they never seemed to make it to manufacturer's production
> lines, just as service parts). But one only has to install Orange Drops
> once. The radio will never need paper capacitors again.
>
> 7. As for testing, I quit testing after the first couple radios where
> 95% of the capacitors tested leaky. When a screen bypass capacitor drops
> the screen voltage just 10%, its reduced the plate current and the stage
> gain by 10%. And in time that extra screen circuit current has added
> heat to the screen dropping resistor to shift its value higher, adding
> to the voltage drop. And when a leaky coupling capacitor has reduced the
> bias on an audio output tube by a volt or two, it has increased the
> plate current by 15 to 30%, shortening the life of the tube, shortened
> the life of the output transformer and added scorch to the cabinet above
> the tube (to say nothing of the operator's fingers doing a tube
> temperature check). Then a few megohms leakage shunting the AGC line can
> cause poor AGC and subsequent distortion but won't show up with ordinary
> voltage checks though the AGC voltage will test low. With the full set
> of maladies brought on by leaky molded oiled paper capacitors that wreck
> a radio's performance, replacing ALL them with Orange Drops saves weeks
> of troubleshooting which won't necessarily show up the individual
> marginal capacitors. Then getting the old caps out with enough leads to
> test and put back is very hard on tube sockets and terminal strips. I
> consider it better to replace after cutting the leads short than to fry
> sockets, wires, terminal strips and other components trying to salvage
> the old capacitors.
>
> In summary: REPLACE THEM ALL, DON'T CUT CORNERS WITH UNKNOWN PART, DON'T
> WASTE TIME TESTING.
> --
> 73, Jerry, K0CQ, Technical Advisor to the CRA
> All content copyright Dr. Gerald N. Johnson, electrical engineer
>