[ARC5] Restuffing electrolytic caps - it won't work??

[Kenneth G. Gordon]

Thank you, Mike. :-)

I guess I should have said, "I sure as heck wouldn't do that....until I knew 
more..." :-)

Now we "know more".

Ken W7EKB


On 2 Jun 2014 at 8:47, Mike Hanz wrote:

> On 6/1/2014 4:52 PM, Kenneth G. Gordon wrote:
> >> My problem with this:  When drilling out the old cap guts,
> >> I can smell and even taste chemicals from inside them
> >> which become aerosolized during the drilling.
> >> I have no idea what I'm breathing-in during this process,
> >> but I don't like it.  Anyone know if my head is going
> >> to turn green and fall off??
> > Probably. I sure as heck wouldn't do that.
> 
> I realize that the conventional wisdom these days suggests we all wear 
> Hazmat suits whenever we enter the radio shack, but AB5S's experience 
> prompted me to investigate the composition of electrolytic capacitors 
> back in the early 1940s, and to dissect examples of both the 5uF and 
> 15uF caps in question.  It's easy to peel back the onion layers with a 
> lathe and boring bar.  Here's the construction that I found in the two 
> examples:
> 
> After removing the top using the pipe cutter tool, you are faced with 
> the picture at http://home.netcom.com/~arc5/Restuff/IMG_3116.JPG  The 
> reddish disk with the eyelet connection on top is actually made from red 
> pigmented rubber - basically a red rubber washer 1/8" thick.  The next 
> layer underneath that is a similar thickness disk of phenolic. This is 
> where the smell come from - anyone who has drilled or machined phenolic 
> is familiar with that lovely aroma.  It's also where the yellow 
> "cornmeal" stuff comes from as you drill down through it.  Beneath that 
> is a paper insulated rolled capacitor. Henney's Radio Engineering 
> Handbook (1941) advises that this design is the latest in technology for 
> electrolytics, and is composed of tightly controlled thickness aluminum 
> foil that has been etched to increase the surface area, and the 
> electrolytic portion of the paper dielectric is...are your Hazmat suits 
> sealed?...wait for it...apparently just ionized water!  Placing a drop 
> of the fluid in the can on a freshly sanded steel surface produced 
> fairly quick rusting.  Okay, Hazmat suits off...:-)
> 
> At the bottom is a slim (.030" thick) circle of phenolic to insulate the 
> bottom side of the rolled capacitor from the bottom of the can. Though 
> not relevant here, Henney also advises that normal oil filled paper 
> capacitors use either castor oil, cottonseed oil, or "transformer oil", 
> whatever that was in 1941.
> 
> As Dave mentioned, the aluminum container for this concoction, including 
> the top rubber washer, is pressed into the brass shell of the 
> capacitor.  The connection of the outer foil to the aluminum can is 
> apparently just direct contact with the can for 360 degrees.  The inner 
> foil connection is through the eyelet.
> 
> I did not remove the pressed-in aluminum cup from either capacitor since 
> everything came out so cleanly, but there is no other apparent ground 
> connection - which begs the question of why there is a ground solder 
> blob between the two screw posts on the bottom of the capacitor.  I 
> hated to destroy one of these two examples, since they are prime 
> material for restuffing.  I suspect there is a simple pressure contact 
> in the bottom of the cup that enhances the ground connection of the 
> inner can, but it will have to wait until I find a more suitable (badly 
> corroded) example to investigate.  In the meantime, I would suggest 
> simply solder sucking the blob off the bottom and drilling a .030" hole 
> through the bottom of the aluminum can for the ground lead of the 
> restuffed caps, then resoldering that ground lead like the original.
> 
> I'll put some photos of this dissection up at 
> http://aafradio.org/garajmahal/Removing_command_receiver_capacitor_tops.html
> later on today when I get some time.
> 
> 73,
> Mike  KC4TOS
> 
> 
> 
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Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne