[Test-Equipment] [TekScopes] esr mETER dISCUSSION

Fri Jul 23 14:37:39 EDT 2010

Long post, but I hope it's helpful to someone!

Hello to all. I have been following these "ESR" threads with great interest. 
One of my first responsibilities when hired by IBM, was to do some 'electronic reliability studies' of both IBM and various competitors. For data, we had access to volumes of manufacturing and field failure rates for some of IBM's largest machines. To add to this, we had Mil-Spec failure rates, Mfgs F/R, etc.
It became quickly apparent, that electrolytic capacitors were kinda short lived, and failure prone.
About 15 years ago, my ham career of 35 years (at that time), turned to "boatanchors", or tube type equipment. Since I had a good job (and thanks to ePay), I was finally able to afford the radios I could only dream about as a teen.
Over the years, I have restored hundreds and hundreds of pieces of ham gear and older test equipment.
After a visual inspection, and test of the tubes (if present), the next thing I examine are the caps. Yes, electrolytics and also 'bypass and coupling' caps. These are usually in the .1 to .01 uf range.
Initially, I also resisted the 'just swap them out' way of thinking. However, the more I restored, the more I learned.

I have an old (1955) Collins receiver (75A-4, 22 tubes) that's worth a bit. I really didn't want to just start cutting and replacing, because they are highly sought after collector items.
This whole subject about replacing capacitors in old radios is a LONG, and HOTLY debated subject. Some folks say NEVER replace them, but the other camp feels that a radio is meant to be used and enjoyed and should be able to turn in it's best possible performance.
Most of the offending caps are under the chassis out of sight, but some 'purists' still consider it heresy to change a bad cap. There are some that will agree that the old caps are in need of replacement and will actually cut open a tubular cap and put an "Orange Drop" inside!!!
Once I started and found out just HOW leaky the old paper caps were in my 75A-4, they all came out. Even one of the Mica caps leaked. The radio needed a realignment but it will hang in (with limitations) with some $3000 receivers.
I still do not do a complete cap swap at random. It depends on the vintage of the equipment. Older radios like the Collins and Hallicrafters, etc from the late 50s to mid 60s are PROBABLY gonna be candidates for a complete recap. However, radios like a Drake, used more modern caps and I have NEVER found a bad cap in a Drake radio, and I own several dozen.
Here's another example: I bought a Colins 51J-3 (18 tubes) radio which was made about the same time as the 75A-4 or maybe a year or two earlier.
The 51J-3 has always amazed me with it's incredible sensitivity and stability. One day, I decided to pull it out of the rack and check it's caps. To my surprise, all the coupling and bypass caps were 'dogbones' and 100% perfect.

Although I have a bunch of high $ commercial cap testers, for small value (NON ELECTROLYTIC) caps, I prefer just a HVPS and a good old VTVM.

For electrolytics, I did a LOT of pondering and finally purchased a Peak ESR meter. Works perfect! Self protection, gives not only ESR but also value. I also have a couple of analog ones, but the meter scaling leaves a LOT to be desired.

The following 'rules' work for me (N4UE):

- caps in the .1 to .01 uf range (NON-electrolytic) coupling and bypass caps MUST be checked for leakage at their rated voltage! ESR can't be measured (at least not on my test equipment) ha ha

- bypass and coupling caps that leak 500+ VDC (out of a 600 VDC rating), will still test exactly at their 'stated' VALUE on any of my high $ LCR bridges.

- DVM sized meters that have a 'cap' function will ONLY tell you the value.

- electrolytic caps should be tested with an ESR meter. My Peak will sometimes measure simply tremendously high/low capacitance versus the stated value.

- electrolytic caps deteriorate with age. NOS caps sitting on some TV repair shop shelf, will probably be NFG.

- today's caps are orders of magnitude better than caps from the past and much smaller to boot.

- this size factor makes it easy to gut an old multi-section 'can' electrolytic and stuff it with modern replacements. Several companies provide this service for those that can't 'do it themselves'.......

- like a lot of things (!!), the old saying: "if ya don't use it, you'll lose it", holds true.
I periodically 'exercise' my collection.

- of the thousans of caps that I have replaced, only 2 ceramic disks were bad (shorted) The old, wax covered ones gotta go!!

thanks fer the time and bandwidth!
ron
N4UE

-----Original Message-----
From: John Chung <kravnus at yahoo.com>
To: TekScopes at yahoogroups.com
Sent: Fri, Jul 23, 2010 1:28 pm
Subject: Re: [TekScopes] esr mETER dISCUSSION

I bought the blue esr meter for this purpose. It is a fine kit and has detected a fare share of bad caps.

John

--- On Fri, 7/23/10, Michael J Wallace <mwallace9 at cfl.rr.com> wrote:

From: Michael J Wallace <mwallace9 at cfl.rr.com>
Subject: [TekScopes] esr mETER dISCUSSION
To: TekScopes at yahoogroups.com
Date: Friday, July 23, 2010, 7:32 PM

Does anyone have the necessary lab equipment and Esr meter to do a side by side if you will comparison and note the results ? 
Irregardless of the validity of such a meter, Ive seen and been told by more intelligent and experienced people than myself that bad capacitors as a root problem are far  more prevalent than most other failures. 

That being said, I would like to know if having such a meter is a preferred method as opposed to just shotgunning capacitors, or if there is yet a better method.
If other equipment is a more reliable and better way to test, then i would like to know a list of such equipment and the optimal as far as accuracy is concerned, test proceedures.

I abhor, in english parlance, the phrase "When in doubt, swap it out". The whole point for me in asking the original question that got this thread started was to learn the correct way to troubleshoot a suspected capacitor failure.

Thank You in advance,
Mike

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