[Hallicrafters] Testing caps

Tue Mar 10 16:23:05 EDT 2015

      I generally agree with all this but differ in the value of a 
leakage tester for elecrolytics and the value of ESR or dissipation 
factor measurement on all caps.  Paper caps like the BBOD can have 
accurate value but high ESR as well as leakage, you really have to test 
for both.  Electrolytics all have leakage due to the kind of dielectric 
but there is a limit beyond which it is too high.  Many capacitor 
checkers will indicate this on the meter.  You must be patient with high 
value electrolytics because they take a while to charge and the leakage 
indication will be high until they are mostly charged.
       I have several alternatives for testing but I have an old Eico 
cap checker that does the job most of the time.  For precise 
measurements of value and dissipation factor I use a General Radio 
impedance bridge.  I also have a General Radio megohm meter which will 
show up leakage in all kinds of capacitors that will tolerate its test 
voltage.  I've also found that my Hewlett-Packard 410-B gives a pretty 
good indication of leakage using the ohm meter function without 
subjecting the cap to very high voltage but the voltage is necessary for 
electrolytics to get a valid measurement.
       BB caps were used in a lot of places beside Hammarlund SP-600 
receivers.  For instance Hewlett-Packard 400 series AC VTVMs are full of 
them but I've never seen a cracked or leaky one where the SP-600 has 
lots of them.  I don't know what the difference is but suspect the heat 
of soldering may be a factor.  The BB was sold as a high quality, long 
life cap. The originals (there was a second series) were oil filled.  
The filling was done by means of a tube in one end which was sealed by 
soldering one of the leads to it.  I think that the seal was often 
compromised by the application of too much heat when they were 
installed.  however, I don't know how this affects the cracked and 
broken cases.  I've also found that the windings in BB's are usually 
distorted.  I thought perhaps they were squeezed to adjust the value but 
I wonder. I've seen similar distorted windings in other brands of 
plastic cased paper caps. However, I've also dissected some Micamold and 
Solar flat paper caps, the kind that look like mica caps. They all had 
high ESR and were leaky but the windings were perfect.

On 3/10/2015 11:29 AM, ron via Hallicrafters wrote:
> 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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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL