Part Need - Can You Help?

[W1UJR]

It always works like this, right?

Just 1 week before the AWA Conference my restoration contest entry decides to spring a leak.
What I believe to be a oil filled cap has begun leaking oil onto the chassis and dripping on the the bench.

I've posted photos of the unit, it is the silver piece, near the rear center of the chassis.
You can see from the back and side views it has held in place by two metal retainers.
On the bottom are four terminals, one being labeled "common".
No other markings are on the device.

I'm assuming its a cap, and if you have a matching unit in your scrap box I'd
very delighted to pay for it and the shipping to get it up here.

I'm going to remove the unit this evening, with an eye toward isolating and resealing the leak,
but given how much oil is on the bench, its best replaced.

Thanks!
-Bruce

[Ed - N3LHB]

Bruce,

Don't be biting your nails or making dinner without washing up first. My guess is the oil is the PCB type. Good luck, OM.

Ed, N3LHB

[W1UJR]

Yep, and its all on my hands too!
Including the cut on the end of my one finger. 
The world end in 2011, so its not going to matter.

I got the unit out, its leaking at one of the soldered seams,
was able to resolder, problem is, I don't know how much
oil leaked out. From the mess on the bench and chassis,
I'd say a good amount.

So I am still in the market for a replacement.

[W2PFY]

Hi Bruce, I can see it's a three section cap. what are the values and the working voltage? I'll look in my stash but a 3 section oil cap may be hard to find.

[W1UJR]

No markings Terry, thats one of the problems.

B plus on the rig is about 800 VDC.

[AJ1G]

Nice looking unit Bruce - what is it and what is it's pedigree?  Nicely made - a W1FPZ project?
Sorry I can't help with a replacement - maybe you can rebuild with modern caps inside the old can. s

I like the old cable lacing...when I was a JN I used to do up all the interconnect wiring in the shack with the real telco waxed cable lacing cord that would occasionally make its way home.  The only problem was that I would need to tear down a lot of the wiring every few weeks as things got moved around!

Anyone know if you can buy that stuff anymore?

[ka3zlr]

Removing those side holding plates doesn't reveal any info either...Bummer..

73
Jack.

[K1ZJH]

Assuming it isn't leaky (electrically, that is) try measuring the sections using a bridge to find the capacity.  You could always open the can rebuild it...  Hide more modern components inside.

Pete

[w1vtp]

Assuming it isn't leaky (electrically, that is) try measuring the sections using a bridge to find the capacity.  You could always open the can rebuild it...  Hide more modern components inside.

Pete

Yep, I've seen that done before -- tho' messing with PCB's aint no picnic

Al

[W1UJR]

Yes, thats a good suggestion Pete, I could gut it and install modern caps if it still leaks.

I think what made it spring a leak is that I might have overtightened the securing clamps.
I used lock and flat washers, but perhaps I just tweaked it a bit too much.

Bummer is it used to belong to Bill Orr W6SAI, and then my friend John W1FPZ.
Spent the winter/spring restoring it, and right be for I take it to AWA it leaks!

Hoping someone out there has one in their goodie box.
But, if I can't find a good replacement, then I'll reuse my soldered up version.
Did some cleaning with the wire wheel on the Dremel tool this evening, was able to solder about 1/2 way around the side that was leaking, pretty easy actually, left a nice fillet.

My big concern is the oil that has leaked out, and how it may have compromised the dielectric of the cap.
I've got a heavy duty cap tester, may check it out tomorrow evening and see if stands up to 1200-1600 volts ok.
I've got it sitting now to check for leaks in the morning.
My big worry is that the seals on the terminals are smoked, if thats the case, then I'm sunk.

I did note two small soldered holes on the bottom, bet these are used for filling the cap during assembly, one to fill with, and the other as a vent.

Thanks fellows.

[WA1GFZ]

Bruce,
I would reseal it and refill it. Do it outside and stay up wind. Open the two solder seals on the bottom and drain the oil out. Do the repair with good solder  and acid flux and refill the can. You need a good hot iron maybe 300 or more watts. Solder one hole shut and let it cool down. Then place the can in some ice water about 1/2 way up the can. Now you have to move fast. Solder the second hole before the oil boils. The Ice should keep it cool and cool it back down quickly. You should get a good mask to be safe. Replacing the guts you will need to drain the can and remove the bottom so you can get at the terminals. You can remove the bottom with a torch going in a circular motion around the seam until the solder softens.
This will make a good amount of PCB gas so be very careful. Remember to insulate the new guts to take the heat of resoldering the seam.
I worked at a place that made many products in sealed cans and learned some cool tricks from a pair of masters.  They could take anything apart so we could make repairs and reseal it like nothing ever happened. There were layers of Felt inside so they had to be very fast.

[Carl WA1KPD]

Looks like an easy one to empty and stuff hiding all of the damage on the chassis

[W1UJR]

Ok, great tip.

What kind of oil Frank?

[WA1GFZ]

I'm sure you could find someone to donate a PCB filled cap you could vampire

[W1UJR]

Oh, add more nasty stuff? 

[WA1GFZ]

The WA2PJP police could check you out and you would not want to be caught with a modified rig.

Chris, Do you know how to tie a MIL- STD knot on a cable lace. Bring a foot or so of string to Deerfield and I can show you.

[W1UJR]

Ah, forgot about the authenticity police! 

Frank, I stay away from anything called STD, but Ill bring some lacing cord, I could
learn how to do it correctly. I laced up the harness on the last rig, it was fun,
but took me FOREVER until I got it right.

What about Johnson's Baby Oil, says PCB free?

[W2XR]

Bruce,

I have in front of me two double-section oil-filled caps that I pulled out of a Lambda tube regulated PSU many years ago.

Each capacitor consists of a common terminal, and a 4 uf and a 2 uf cap section. Each cap section is rated at 600 VDC. The terminals are solder lugs.

They are the classic silver color of that period, and condx.-wise, I'd give them a 9 on a scale of 1 to 10.

Here are the outline dimensions per capacitor: the overall height, less the solder terminals, is 4.5", the depth is 1-3/16", and the width is 2.5". I may have the mounting clamps as well. If you mount them with the 2.5" width dimension facing each other, you may be good to go, assuming the values and voltages are correct for the application.

The pair just may suffice for your intended application, and they look period-correct.

The W2XR Spare Parts Department could arrange emergency overnight delivery to get things right at your end. Just let us know.

73,

Bruce

[WA1GFZ]

Bruce,
I'm not sure of a good oil to use but I bet someone here can suggest something. it will need to mix with the pcb oil left behind.
once you learn the knot it will be much easier to lace a cable and it will be as tight as you want it. This is not the daisy chain knot thing used in some old rigs. But I supposed this would be the perfect fitst knot.

[AJ1G]

I learned the daisy chain lacing method - remember the illustrations of it right way and wrong way in the '64 Handbook that I had on more or less permanent check out from the Jr High and then the HS library.

[W7TFO]

I'd go for the baby oil.  AKA mineral oil.  Same thing they dehydrate a bit and put in new caps. 

Heck, I'd just solder it the leak up, drill two little holes (one top, one bottom) and drain it.  Solder the bottom one up, fill it with an eyedropper, and just solder up the other.  Or did someone already say that?

Maybe heat the oil a bit first, so when it cools, it will pull a bit of vacuum.  Sorta like canning fruit...

[DMOD]

I would use a PAO heat transfer fluid for the oil replacement. I use it in dummy loads. Very safe and it's good to 575 F. Dieletric strength is > 35KV.

I am getting a 5-gal. pail here shortly, so let me know if you want some.


Phil - AC0OB

[W1UJR]

W2XR, thanks for the offer (and photos the other day) OM, but I need to stay with something close to the original, not much space for two caps.

I was able to solder up the case last night, and it sat on the bench with no external leakage.
Nice thing is that the retraining strap will cover my soldering, and once painted should look quite nice.
If its still dry tonight, I'm going to reinstall it for the AWA Conference, it will be on static display there anyway, and keep looking for the exact replacement.

Tnx for the offer of oil, if I can't find the matching cap, I'll gladly take you up on that, but would rather limit my
exposure to PCBs in the old cap.

In retrospect, I do think that happened is that I must have over tightened the retaining straps, a little too strapping if you will,
and broken the solder seal on the base.

The vintage of the rig is the mid 1930s, and the cap is clearly a later installation as it appears to be mil type with
MFP coating on the bottom near the terminals. I don't commonly see oil filled caps in low power amateur gear from the 1930s.
It is clear that over the years various components have been replaced, at least one of the xformers look more recent as well.

Thanks for the quick response and suggestions fellows, and if one of you digs up a replacement cap, keep me in mind.
Sure that lots of these got trashed because of PCB concerns.