Sweaty, but only some, from the US long ago. - UK Vintage Radio Repair and Restoration Discussion Forum

Boater Sam · 12th Jun 2018, 1:55 pm

The 1946 Timespot S25 has made it to the bench.
Underneath there are the common Sprague aluminium canned capacitors, 5 of them and another one on top.
These are the ones from the US surplus market used by lots of set makers in this post-war period with the end caps rolled in.
I have found these to be very reliable and seldom need to be replaced except I always check and change the audio grid coupler just in case.

Now this set has 3 of these in a plastic sleeve, one being the said coupler. The rest are naked.

Oddly the sleeved 3 are all "oily" and look as though they are sweating a greasy substance that is difficult to dissolve with IPA both inside and outside the sleeve. The other 3 are perfectly dry.
Why the difference caused? by the plastic sleeve? Or is it the sleeve that is breaking down and degrading back to oil?
These sleeves are quite thick, turned a bit yellow/brown, and have the texture of a thick condom. ( excuse the description but it is apt )

I have cleaned up the coupling cap, its slightly electrically leaky, 15M ohms, gone from 20nF to 30nF so it will get restuffed anyway. Since cleaning, it is staying oil free.

Are the Spragues oil filled to the extent of having enough free oil to drip?
But if so, why are only the sleeved ones leaking?

Sam.

dazzlevision · 12th Jun 2018, 3:07 pm

Possibly plasticiser leeching out of the plastic sleeves ...?

Boater Sam · 12th Jun 2018, 6:45 pm

I've come to the same conclusion, having stripped all 3 capacitors and restuffed them I found that they had sufficient oil inside to soak the paper but not enough to explain the amount outside. The inside of the aluminium can has a brown paper lining, then the paper and foil wrap. The end caps are quite thick paxolin, crimped into the ends up to the groove in the body. No signs of an oil leak on any of them.

They are fairly easy to drill out one end and replace the guts. Oddly the other 3 without sleeves are still serviceable!

12th Jun 2018, 1:55 pm	#1
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Sweaty, but only some, from the US long ago. The 1946 Timespot S25 has made it to the bench. Underneath there are the common Sprague aluminium canned capacitors, 5 of them and another one on top. These are the ones from the US surplus market used by lots of set makers in this post-war period with the end caps rolled in. I have found these to be very reliable and seldom need to be replaced except I always check and change the audio grid coupler just in case. Now this set has 3 of these in a plastic sleeve, one being the said coupler. The rest are naked. Oddly the sleeved 3 are all "oily" and look as though they are sweating a greasy substance that is difficult to dissolve with IPA both inside and outside the sleeve. The other 3 are perfectly dry. Why the difference caused? by the plastic sleeve? Or is it the sleeve that is breaking down and degrading back to oil? These sleeves are quite thick, turned a bit yellow/brown, and have the texture of a thick condom. ( excuse the description but it is apt ) I have cleaned up the coupling cap, its slightly electrically leaky, 15M ohms, gone from 20nF to 30nF so it will get restuffed anyway. Since cleaning, it is staying oil free. Are the Spragues oil filled to the extent of having enough free oil to drip? But if so, why are only the sleeved ones leaking? Sam. Last edited by Boater Sam; 12th Jun 2018 at 1:56 pm. Reason: added

12th Jun 2018, 3:07 pm	#2
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,608	Re: Sweaty, but only some, from the US long ago. Possibly plasticiser leeching out of the plastic sleeves ...?

12th Jun 2018, 6:45 pm	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Sweaty, but only some, from the US long ago. I've come to the same conclusion, having stripped all 3 capacitors and restuffed them I found that they had sufficient oil inside to soak the paper but not enough to explain the amount outside. The inside of the aluminium can has a brown paper lining, then the paper and foil wrap. The end caps are quite thick paxolin, crimped into the ends up to the groove in the body. No signs of an oil leak on any of them. They are fairly easy to drill out one end and replace the guts. Oddly the other 3 without sleeves are still serviceable!