Oil Cap Testing

[ka4koe]

Is there an established way to test oil / paper caps other than applying power whilst behind bulletproof glass? I intend to check everything I can in this old Gates.

Tnx.

Philip

[KA2DZT]

What brand oil caps are they??

[ka4koe]

Gates, or what Gates provided with their transmitters. One can test for resistance using a VOM, but don't know if this adequate.

[N8ETQ]

   Hey Phil,


          Hard to say, they are amazingly resilient.
Here is one I found in an HT-33? that was repaired
in the past with "Lead" and was not shorted. Even
held its Value.

         I swapped it out with a string of Modern
electrolytic's none the less. I'm sure new ones are
obtainable but can't imagine what they would cost.
I don't think swapping a 50 year old cap out with
another 50 year old cap makes sense.

GL

/Dan

[KA2DZT]

Gates, or what Gates provided with their transmitters. One can test for resistance using a VOM, but don't know if this adequate.

Philip,

Gates didn't make the caps, take a look at them.

You have to put high voltage on them to test them.  Bring them up in steps, use a current meter to measure the leakage current if any.  Put a resistor in series to limit the current.

I have a regulated high voltage power supply that I use, but it only goes to 1500 volts.  It has a current meter in it.

Unlikely the oil caps are bad, but doesn't hurt to test them as best you can.  Forget the ohmmeter.

Fred

[N2DTS]

I have never had an oil filled cap go bad or fail, despite running them way over voltage at times.
Electrolytics fail all the time, and will not put up with any over voltage, and just plain suck for high voltage.

Unless space was critical, I would always use an oil filled cap over a crappy electrolytic cap.
Many used here were old when I installed them 30 years or more ago and are still working fine.

I would not even bother to test any, if they are not leaking, they are good to go.

[WZ5Q]

I just slowly bring the HV up on them.

I can't wait to slam the HV to these bad boys...

[w4bfs]

time to get or make a dc hi pot tester .... a good use for a small hV xfmr .... ballast the primary with small incandescent light bulband can use small neons on secondary side for sensitive current detector

can't live without it

[W7SOE]

I just slowly bring the HV up on them.

I can't wait to slam the HV to these bad boys...

I get a little scared looking at those.  ;-)

Rich

[kg7bz]

I just slowly bring the HV up on them.

I can't wait to slam the HV to these bad boys...

They'll slam it back to you, 5635 Joules storage each! Those are Dangerous!

I've had fun with caps like that.

[ka4koe]

A defibrillator uses 360 joules maximum, per K4SMN.

[W6TOM]

  One issue no one has mentioned, what about PCB Oil?? My employer has a transformer rebuild facility near here, I'm talking utility transformers, pole pigs and ones used on pads and in vaults. They take the PCB issue seriously, the first thing they do is take an oil sample to check. Old as that transmitter is I bet the oil is PCB.

[KA2DZT]

  One issue no one has mentioned, what about PCB Oil?? My employer has a transformer rebuild facility near here, I'm talking utility transformers, pole pigs and ones used on pads and in vaults. They take the PCB issue seriously, the first thing they do is take an oil sample to check. Old as that transmitter is I bet the oil is PCB.

So long as you don't drink too much of it you should be OK.  Probably something is not right, by today's standards, with a lot of this old junk we all play with.

[W9ZSL]

Chances are the caps are PCB filled.  When I salvaged a BC-1T years ago, the caps had all been pulled presumably because they were hazardous.  I know they weren't bad because I was on the air the day the plate iron shorted out and though the xtr had been dropping off the air more frequently, it sounded fine on the monitor until the final shutdown.

[KA0HCP]

  One issue no one has mentioned, what about PCB Oil?? My employer has a transformer rebuild facility near here, I'm talking utility transformers, pole pigs and ones used on pads and in vaults. They take the PCB issue seriously, the first thing they do is take an oil sample to check. Old as that transmitter is I bet the oil is PCB.

What about it?  Seriously.  If it isn't leaking it's not a problem.

And, not all oil transformers used PCB oils.  There are lists of known brands/lines that used PCB's. 

IMO, it's not much different than finding asbestos in a building.  If you don't open it up and release it, there isn't a problem.  b.

[WZ5Q]

As long as I'm not soppin my biscuits in it or taking a bath with it, I'll be just fine.
If there's a problem, then I'll don the PPE, clean up the mess, then slap in the next one and throw the switch.

[KA0HCP]

Here is one listing of known PCB containing capacitors and information about them.
From Australia/New Zealand health services. (attached below)__

US EPA listing of PCB Trade Names:  
http://www.epa.gov/wastes/hazard/tsd/pcbs/pubs/aroclor.htm#tradenames


UN document with Trade Names, models, identification, more info
http://www.chem.unep.ch/pops/pdf/PCBident/pcbid1.pdf

[w1vtp]

I vote for testing them.  Use a HV source with a current limiting resistor in series with a volt meter rated for the supply in case the caps have high leakage (which is unlikely) or develop a short (again, unlikely).  That way if you have put any beautification into your HV PS, you won't be drilling and blasting to make room for another cap.

Al

[ka4koe]

Cleaned the gunk from the caps. None appear to be leaking. This is a good thing. The 8 mF is a Sprague.