[Hallicrafters] Testing caps

Tue Mar 10 14:29:00 EDT 2015

There have been a lot of excellent replies here, even though I admit I've not read them all, yet.

Please allow me to flog the dying equine one more time... FWIW

I've been collecting boatanchor radios and test equipment for most of my 50 years in Ham Radio..... I have a LOT of both.
For example, I currently have 19 o'scopes, dozens of signal generators, you get my point.

I have replaced thousands of caps in my career. I wait until I have a small bucket full, then toss them. Although there is a HUGE market for BBODs on eBay!!!
>From MY experience, one needs 3 pieces of not very expensive capacitor testing instruments to cover the possibilities.

Frist, let me state in all these years, I have found exactly TWO bad disk caps. One was broken by a previous ham-fisted owner and the other was internally shorted. I have NEVER found a defective 'dogbone' cap. My Collins 51J-3 is full of these and is still working 100% and never been touched.

1. Inexpensive DVM style cap VALUE tester. I have several and also a NIST Traceable LCR Bridge. These usually run off a 9V battery. As stated, they will indicate the value of a cap (great for variables), but tell you nothing about 'leakage'.

2. ESR meter for electrolytic types. I have several but am kinda biased toward my Peak (brand). Not only will it automatically discharge an electrolytic cap and give you it's VALUE, it will also tell you it's ESR.

3. High Voltage Leakage Tester. This is absolutely necessary for testing coupling / bypass caps, typically .01 or .1 UF. I have a collection of these, such as TO-6A, TO-5, ZM11/U, on and on. Honestly, on my main test bench, I use an old Heathkit IM-11 (cap checker) that it's only function is it's nice adjustable HVPS. This is used in conjunction with an old VTVM. You can't use this method for electrolytics since if good, they ALL leak.....

Here's a perfect example of testing the caps in my SX-101A or my 75A-4.......

Disconnect one end of the BBOD or 'bumblebee' cap and put on a VALUE tester. Almost guaranteed it will measure it's exact, rated VALUE.
OK, now put 400 or 600 VDC (whatever it's rated at) by connecting the LEAKAGE tester. Usually they will leak 500+ VDC with 600 VDC applied.
OK, I admit it might not make a huge difference on a bypass or decoupling cap, but think what that HVDC is doing to the next stage when it's connected from Plate to Grid.....

On my 75A-4 and SX-101A, I did one cap at a time and noticed the slow improvement as I progressed. Every single 'black cap' in both radios leaked horribly. In the 75A-4, I also found a leaky Mica cap which is not that unusual. Now, I just replace all the usual suspects and test every Mica I come across.

Thanks fer listening...

ron
N4UE

-----Original Message-----
From: Roger D Johnson <n1rj at roadrunner.com>
To: Jim Liles <hallicrafterssr2000 at k9axn.com>
Cc: hallicrafters <hallicrafters at mailman.qth.net>
Sent: Sat, Mar 7, 2015 3:24 pm
Subject: Re: [Hallicrafters] Black Beauty capacitors Beware

It seem to be throughout the lines. S-76, SX-96, SX-100, etc.

On 3/7/2015
2:45 PM, Jim Liles wrote:
> Hi Roger,
>
> What model?
>
> Kindest regards
Jim K9AXN
>
> -----Original Message----- From: Roger D Johnson
> Sent:
Saturday, March 07, 2015 1:08 PM
> To: hallicrafters at mailman.qth.net
>
Subject: Re: [Hallicrafters] Black Beauty capacitors Beware
>
> The cold ends
of the first set are at RF ground due to a bypass cap. I just
> can't figure
out why Halli
> would put B+ on one set of caps and not on the other!
>
> On
3/7/2015 2:05 PM, Roger D Johnson wrote:
>> I've just noticed something strange
about these IF strips that I hadn't seen 
>> before. The first set of
>>
capacitors on the selectivity switch have the cold ends connected to B+ while

>> the second set has
>> the cold ends grounded. Anyone know why
Hallicrafters did this?
>>
>> 73, Roger
>>
>>
>>
>>
>>
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