The AM Forum

The Oil filled high voltage capacitors used in broadcast transmitters of the 50's and 60's had PCBs in them. I have been told that as long as these are not leaking, they are usable. True ? Do these caps ever go defective otherwise ?

That is a tough call.
All the old ones likely have pcb's inside, blow one up and you have pcb's in the house long term, a real toxic waste dump.

I have a lot unused, and quite a few in use, never blew one up or had one leak (that I did not drop).

Brett

 

What vendors sell replacement high voltage caps ?

<What vendors sell replacement high voltage caps ?>

Plastic Capacitors Inc makes a wide variety of oil and film capacitors including high voltage ones.

Not cheap.

I have had good "luck" with the older caps with PCB's in them.  I never use the ones that leak for obvious reasons but I have never had one go bad.  In rare cases they do go bad but not often.  Both of my Gates BC rigs have the original oil filled caps in them and never had a problem.  They were manufactured in 1941. 
Joe, W3GMS     

Unless you hit the lottery, you wont want to buy new oil filled caps, but can find them at fests or on ebay for reasonable prices. The plus side of modern caps is they are typicly smaller than the old ones.

I got some at a fest marked pcb free, 24uf at 2500 volts for very little.

Plastic capacitors makes some nice ones, quite small for the spec's.
I have a few of those.

If you mess with tube stuff, you have to go to the bigger fests to find good parts at reasonable priices.

Brett

Like Joe, my Gates (BC-250GY) has the original oil caps and they are fine.  The filament transformers for the rectifiers were leaking oil but I dumped those and the tube type rectifiers so problem solved.

I wouldn't use a leaking cap but I don't worry excessively about PCB caps.  If they leak, contain the mess and clean up and dispose of them properly.  I remember one of the universities had a problem a few years ago when a group of graduate students were sent in to clean up an old lab and several of them were exposed to PCB from a bunch of old capacitors.  The big problem in this case was that the students were not cautioned about the hazard so several of them got and kept it on their skin for several hours.  As I recall there was not any severe problems from this particular exposure.

Next fear, those miniature VR tubes with the radiation warning symbol on the side  :)

Rodger WQ9E

Everyone makes such a big deal over PCBs. I used to work for a company that did oil and chemical spills, tank cleaning, and chemical clean ups. This was 30 years ago.
I have gotten doused head to toe with PCB transformer oil at one time or another.
the recomended cleaning agents were mineral spirits (oil based paint thinner / lighter fluid) or just plain old fashioned soap and water!

Since PCB is a fire retardant, in my opinion that makes the capacitors safer and more desireable

That whole PCB thing (at least for us) is much to do about nothing, since the only way it is harmful is if you ingest it!

The bottom line is dont lick or eat your capacitors! !  ;D  ;D

                                                                 The Slab Bacon

Slab,

Are you telling me I have to use a different grease in my cast iron skillet???  That old capacitor oil works so well because I can get the skillet really hot without having the grease smoke.  Breakfast is going to take a lot longer to cook now!

Next you are going to tell me I shouldn't be saving the radioactive isotope from broken VR tubes to make my own backup power source...

Backup power source ???  ???  WTF

Rodger, where in the hell have you been hiding?? You are supposed to grind that stuff finely and mix it with the breading when you fry your chicken in the PCB oil. It gives it a real nice crispyness and that High-tech taste  ;D  ;D

I'd really like to see the double-blind test on that one, um hmm.  You'd have to have everything set up exactly the same, source to ear; even the amp and speaker and ear placement in the room (impossible save in a perfectly infinite 3d space, not to mention one amp capped with quality propylenes vs. the 'superior' one capped with oil filled.

Oh, -no speakers or room?
...How fast can you simultaneously take those separate earphones on and off?
Oh and nobody's ears are perfectly matched either, between the brain(?) or with others'.  ;D   Dual sets of reproducers inside the phone cups?   Phase and axial placement difference, etc..    and so forth. 

If anyone is interested, I have a 20mfd @ 20,000 volt cap. Its pretty large. It is also PCB free, according to the label. If you want it, come get it..............ITS FREE.
Regards,
Gary...WZ1M

bull pucky

That's way too much Free! Hams are cheap, it may have to be even more free.


One suggestion when using oil caps. If possible always mount them with the bushings pointed up. If they are pointed down, they will leak in time. I had one like that in my Westinghouse and it was dripping PCB's right down on a HV fuse area. I wasn't worried about a fire but It did make for a messy  clean up. Now the rags and cap reside in a plastic bag. Where would one take this cap to be disposed of properly?

In this state with GE and the Hudson River clean up going on, you might be carted off to jail for the mere mention of a PCB product in your home.

dunk yer interstage transformers in oil. Just stick em in the teacup with the leads sticking out. you wont believe the huge erect throbbingTESSITURA you get!

PCB and global warming scares are started by the same lunatic fringe.

As mentioned by many, if it doesnt leak its fine. They do not develop internal leakage as do paper caps or electrolytics either. The failure mode is a short 99% of the time from over voltage and a HV fuse is considered a smart idea in any amp.

Be very careful of modern caps on Ebay and hamfests. Those are most likely used as storage caps for various modes of pulse service. The ESR is high and not compatible with our type of PS, especially in doubler service and there have been many, many reports of them letting loose with a bang. At 50-60% of voltage rating they seem to hold up OK and Ive been runing a few 5KV ones at 2500V for years. Always keep checking case temperature during initial use, they should barely go above ambient. Never operate any HV cap on its side.

Carl
KM1H

In 50 years of hamming, I think I have seen two oil caps go bad.  They shorted internally and the worst result was a blown fuse.  If operated within their ratings, the things are practically indestructible. I have never heard of one in a power supply exploding. Electrolytics are the ones that tend to explode.  I probably have a total of several gallons of PCB oil in the capacitors in my transmitters and in my spare parts collection. Add that to all the mercury in my 866A's, 872A's and 575A's, and my shack would likely be declared a miniature Love Canal.

I have seen oil caps leak around the insulators, with a slight oily residue. Once or twice I have seen leaks at spots on the seams where the case appears to be soldered together.  I have dropped one or two and punctured the case, and they leaked big time.

Sometimes the oil appears to be similar to lubricating oil, and in other capacitors it is more like a gel.

I have repaired leaky caps by first cleaning the leaky spot with degreaser, and then sealing the hole with epoxy.  That always appeared to stop the leak.

Capacitors with non-PCB oil usually have a notice stamped on the case.  I have seen them at reasonable prices at hamfests, often no more expensive than PCB ones.

I recall reading somewhere that the real EPA paranoia over PCB is that it turns to dioxin (nasty stuff) at high temperatures, and they are worried about fire in the storage building or equipment where they are in use.

PCB was reportedly once widely used in brake fluid. If that is true, undoubtedly the amount that got into the environment along highways would make the total PCB contamination from all existing amateur power level transmitting components about comparable to urinating in the ocean.  Where do you think all the brake fluid has gone whenever you have to top off the master cylinder?

When I got my Gates BC transmitter, there were yellow PCB decals stuck all over the oil capacitors as well as many non-PCB components like open frame transformers and enclosed relays.  There was even one affixed to the transmitter door.  I pulled them all off.  There were a couple of large ones, about 8"X8" that I recycled just for the hell of it, and stuck on my rust-infested S-10 pickup truck.  I don't know if it ever grabbed anyone's attention to see that POS chuffing down the road with rust flakes falling off as it went, and the PCB warning labels stuck to the back of the tailgate and the passenger side of the truck. ;D

One of the most outrageous PCB-paranoia stories I ever heard was about 15 years ago when a ham out west rang me on the phone asking about retired tube type transmitters or where he might find an AM transmitter or the parts to build one.  He said he had located a discarded KW broadcast rig that used a pair of 833A's modulated by a pair, but the station manager wouldn't let him have it out of fear of liability in case the PCB in the capacitors ever caused any kind of problem anywhere, any time in the future.  The ham even offered to remove all the oil capacitors and leave them behind for the station owners to dispose of "properly", but the manager wouldn't budge on the issue. He was afraid that any component inside the transmitter cabinet might somehow be contaminated, even down to the 833A's, and insisted that the whole thing had to go to a licensed HAZMAT disposal site. I sniggered at the thought of what they would have to pay a licensed hauler to transport a 1000+ lb transmitter to the disposal site, and the fee the site would charge, since both hauling and acceptance fees are likely based on gross weight. But what a shame that transmitter would be destroyed.

Once or twice a year, they have a local "household" hazardous waste disposal event near here.  They will accept common household and automotive chemicals, such as cleansers, used crankcase oil and old paint, but they specifically state that they will not accept "industrial waste" items. For years I had a 5-gallon can full of transformer oil drained from some pole pigs, plus a gallon can of X-ray transformer oil.  I finally took it on disposal day and told them it was "brake fluid", and they accepted it without further ado.

Delmar, N.Y.

Been using oil caps for years. Never blew one up, and I do not push them to their voltage ratings. I do not use the PCB ones in equipment in the house.

On a devious point, one could buy a stamp that says "NO P.C.B.s" and stamp all one's caps in case the environazis come snooping.

Well, yeah, if you replaced old leaky old wax paper caps with anything modern you'd hear the difference based on bias swamping, interstage voltage leakage, ..you name it. But notice I mentioned comparing to modern, reasonably priced and well working non-oil capacitors in a double blind test.

Did you change out 1940's/50's/ early 60's crappacitors in those amps or did you change out poly's to the oil filled and did you do a double blind test, ca'mon?  ;D

"The Audio Amateur"(TAA) has very stringent outlines for double blind tests if you can find some copies.   ...and that was older technology.  Good procedures are timeless.

PCB has the interesting property not only of being non-combustible; it is an excellent thermal conductor, but an excellent electrical insulator.  Most substances, metal for example, that are good electrical conductors are also good conductors of heat, and vice versa (glass for example).  This makes PCB excellent for transformers and capacitors where you want good insulation properties while getting rid of the heat.

You sound so sure.
Did you ever read any research?

What if you are wrong? Is there the slightest posibility that you are wrong?

I used to work with a huge amount of toxic stuff in work, lead, fermaldihyde?, pumace type abrasive, asbestos, and I am still alive, so its all BS. Its just a coincidence most of the other people that worked there died of cancer, some while I worked there...

I also got across high voltage a few times and THAT did not kill me, so that is BS also. All hype.
(I also once got struck with lightning, true story)

That may be why I am like this now...


Brett

???

56 Farm Game Rd.

Is it not a fire hazard?
When pole pigs blow up, there is always a good fire, one went behind a factory I worked at long ago, set fire to the pole, the grass, the building behind us....

I always worried about the can tenna filled with oil, nice if that stuff lit off, blew the lid off and set fire to the house....
I got a huge dry dummy load I use, but still have the cantenna...

I also have a huge halon fire extingusher in the shack.


Brett

Pole pigs no longer use PCB.  When they did, it was mostly oil, with PCB added, not pure PCB. 

I have friends who told me stories of working for the power company servicing sub-stations, and burning rubbish saturated with transformer oil in 55-gallon drums as a source of warmth during cold weather.

I've actually heard of some beanbrains who bought cantenna type loads and, being too cheap to buy the proper oil to fill them, substituted with cooking oil. I would suppose that should give quite a show if the right conditions were met.

Phil

Not to mention probably some very tasty chicken if you had some around.

PCB Toxicidity is based on human consumption over a period of years (eating it).

It is thought, key word  "thought"  to be cancer causing if eaten. This has not been proven with research on humans, only in animal tests.

I don't plan on eating any if one of my caps blows.

Many workers in the electrical industry were heavily exposed in the pre 1970s times and there is no study showing they were harmed.

It would be interesting to know how many people were killed in fires caused by oil filled transformers after PCBs were banned.

Most pole transformers have mineral oil in them.  They rarely had PCBs except from contamination. Most power companies pooled the mineral oil in tanks and it was contaminated when oil from a special PCB tranformer was mixed with the mineral oil in the tank. No one at the time really cared about the mixing. PCBs were expensive compared to mineral oil and were used in transformers inside buildings or in areas that were a fire hazzard if the transformer exploded.

The trade names for PCBs were Pyranol and Askerel.

Toxic waste is a stupid misnomer - Most household chemicals and even foods are considered toxic if they enter the waste stream.

There are many extremely toxic chemicals that I do not want to have around my home - there needs to be some common sense used in classification of these chemicals - rather than scaring the public by branding everything that can cause any harm "toxic waste".

Cooking oil and table salt may be toxic to some wildlife when poured into a stream - but it should not be classed the same as Sodium Cyanide.

I was the Toxic Waste officer for a very large printing operation for many years. The laws and the procedures were senseless. An oily rag was classed the same as Chromium sludge.

Years ago, I attended a seminar put on by the US Attorney in South Carolina. Two items caught my attention.

The first was,  at that time over a trillion dollars had been spent on superfund cleanups - 100% of that money was for attorney fees - at that time not one cent had been spent on cleaning up anything. This was roughly 1990.

The other item was a small town sewer supervisor in SC had several times opened a valve and let raw sewage run into a small creek during severe storm flooding - in order to keep the main tanks from overflowing - he had done so on orders from the town council but he had the waste treatment license and was responsible. He got 5 years NO PAROLE. The US Attorney that prosecuted him (he was giving the seminar) said that he expected that no way the jury would find him guilty - but they did and with  the new sentencing rules , the judge had to give him 5 years in prison. He was turned in by an enviromentalist after reading about the sewer plant flooding problems in the newspaper.



Pat
N4LTA

Might not be a bad substitute - The flash point for peanut oil is about 320 degrees C

The minimum required flash point for transformer oil is 140 Degrees C.

Other properties such as heat carrying ability might make the cooking oil worse.


Pat
N4LTA

   



Bring it to Nearfest Gary

Carl
KM1H
 

I used distilled water in my Cantenna for a while. Worked FB.
I now have mineral oil in it though. No difference that I can discern.