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Does anyone have any idea what caused this "crud" on the outside of all the electrolytic caps in the power supply of a 422 scope?
I got this 422 scope out of a junk yard in Turkey around 2014. It was in a covered shed for a few years before I found it.
When I found it, the caps and several other parts looked like this:

/g/TekScopes/photo/293345/3753427?p=Created%2C%2C%2C20%2C2%2C0%2C0

Never seen anything like it. Fungus? Mold? It was not on other parts on the PC board, controls, etc.
Mostly the caps. I replaced them all of course, but curious what it is.
BTW, after replacing all the caps, it WORKS!

THanks, Grayson

Grayson-
I have seen that on some other pieces of equipment stored in damp environments. not sure of the actual cause...
BTW my little 422 works great too!...i love the battery capability.....
搁别苍é别

It looks like white mold. It affects certain plastics where cellulose acetate butyrate was one of the ingredients. The mold literally feeds on the cellulose.

On 2/29/2024 5:25 PM, Grayson Evans wrote:

Does anyone have any idea what caused this "crud" on the outside of all the electrolytic caps in the power supply of a 422 scope?

I concur with Polaraligned that it is likely the white mold which affects plastics containing cellulose acetate butyrate. I have seen plastic handles of tools stored in a damp place with that mold.

Do you know who made those caps? I have seen many caps with a yellow jacket similar to those which were made by Sprague for the early generations of HP instruments. None that I have seen, though, had mold, perhaps because they had always been in a dry environment.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA

I've seen this many times on old electrolytic caps, only on that clear plastic rubbery kind of tubing, as I recall. I don't know the cause, but I could go along with the mold hypothesis. If it's not that, then it would have to be some kind of chemicals leaching out of the plastic and reacting with water and/or air, leaving the crust of reaction product(s).

However, I've also seen white powdery deposits on other things too, especially from damp conditions. Some are clearly chemical like from corrosion on aluminum, but may be organic too. There are so many kinds of bacteria and fungi around, just doing their thing, recycling materials back to nature. If you flip over an old pile of dead leaves outside, you might see whitish powdery stuff there too. Same stuff as on caps? I dunno.

If you have a good enough microscope, you may be able to tell if it's microbes or crystals or powder.

Ed

Looks like the plasticizer leached out of the PVC sleeves, then
crystalized.

73,
Bob Weiss N2IXK

Seem like the mold theory on certain plastics is a good idea.
I also see it on some plastic sleve insulation that Tek put over connection points and test points.
All the caps effected has a plastic outter cover. The ones I can read are Spraque.
It is quite hard to get off, furtunately it is not on non-plastic surfaces.

Thanks for the info!

Grayson
KJ7UM
Check out Hollow-State Design
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This mold happens on plastic knobs also. I take a heat gun to the knobs and the mold just disappears.

I have seen these on my capacitors too. I do not think this is mold. I asked around on other forums, and the unanimous answer was the plastic around the cap degrading. Sort of like the fat that comes out of rotting meat.

I also see it on some insulated wire, but not on all the wire. Since it is so selective, I still think the mold theory is best.
I looked at it on a 10x magnifier and still cant tell what the heck it is. Definitely dont want to breath it!

Grayson
KJ7UM
Check out Hollow-State Design
tinyurl.com/hollowstatedesign3 <>
My technical blog:
kj7um.wordpress.com <>