[Test-Equipment] Sprague TO-6A question

[Howie]

If you mean 50k with a vtvm or vom,that thing was leaking like a sieve!

I want that cap please?

I`m repairing a cap checker and don`t have a leaky cap.

Anyone have a shorted Electrolytic I could have?

50k means 50,000 ohms.

----- Original Message ----- 
From: "Ken Kaplan" <krkaplan at cox.net>
To: "Discussion of Electronic Test Equipment" 
<test-equipment at mailman.qth.net>
Sent: Friday, January 22, 2010 3:37 PM
Subject: Re: [Test-Equipment] Sprague TO-6A question


> Yes, I checked the old C16. It measures 50K which I think means 50K
> megohms or 50 gigohms. Seems like enough but I guess not for the
> circuit. The new replacement indicates infinity. I know the other tests
> are not of much value but I wanted to gather as much info as I could. My
> new replacements are Mallory metalized polyester. You think polyethylene
> film would be better?
>
> Ken
>
> k4pf at juno.com wrote:
>>
>> Hi, Ken
>>
>> Glad to help!
>>
>> Did you try measuring the insulation resistance
>> of the removed C-16 cap with the fixed Sprague TO-6?
>>
>> An ESR meter isn't a good check
>> for a small paper capacitor, because everything except
>> a shorted cap will show up as >99 Ohms.
>>
>> A digital capacitor tester is also not a good test
>> to find leaky capacitors.  Try it with a good mica
>> or ceramic capacitor and see how little the reading will change
>> with a parallel 1 Meg resistor added.
>> My B+K model 830 digital capacitance meter is useless in this regard.
>>
>> The Sprague tester does very well at spotting leaky paper capacitors:
>> You will see that the eye tube doesn't indicate a sharp null,
>> it is as if the null were diffuse, smeared around the dial
>> when doing a capacitance measurement on a leaky paper capacitor.
>>
>> One hint: don't forget to renew the paper capacitors used
>> as the "standard" capacitors C-9 and C-10 in your Sprague TO-6A,
>> or even a perfect test capacitor may produce a diffuse null.
>> Polyethylene film caps would be a good choice for the standards,
>> and you can use your digital capacitance meter
>> to select the standards for high accuracy before installation.
>>
>> 73,
>> Ed
>>
>>
>>> Ken Kaplan <krkaplan at cox.net> wrote
>>
>> You got it! I should have looked at the schematic but I think I got a
>> bit lazy. Actually I was in the process of recapping a Hallicrafters
>> SX-100 & thought I'd test what I had just removed. Looks like I better
>> recap the TO6 first. If the test equipment isn't any good, there's no
>> point in digging into the radio.
>>
>> Funny thing is I tested C16 after installing its replacement and it
>> looked ok. I measured its value on a digital tester and it was within
>> 10%. I checked its ESR and found that it was > 99 ohms.
>> So I don't know what to think.
>>
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