Sticky LEM Silver Mica caps - UK Vintage Radio Repair and Restoration Discussion Forum

Petedox · 28th Nov 2022, 9:59 pm

I've replaced a few waxies on my latest project, but was wondering how reliable the above are.

They are not quite waxy, more 'sticky'. The first one I checked was fine, but I'd welcome any views - they're not too easy to get at!

high_vacuum_house · 28th Nov 2022, 11:32 pm

I think they will be fine. The outside of them is a bit sticky and covered in dust, though as long as they are not disturbed mechanically, silvered mica type capacitors are usually very reliable.

Christopher Capener

Petedox · 30th Nov 2022, 4:53 pm

That helps put my mind at rest. Thanks Christopher.

Craig Sawyers · 30th Nov 2022, 7:34 pm

I'm looking at some NOS LEMCO 1500pF +/-5% mica on my desk as I type. Exactly the same as in your set, wax coated.

They measure just fine - well within tolerance, and low loss on my bridges (note the plural!)

So I would say you have nothing to much to worry about with them in your set.

Craig

Lloyd 1985 · 30th Nov 2022, 7:36 pm

I’ve normally found them to be reliable, but a few years ago I was restoring an Ekco A22 and I found both of the 2 on that chassis to be faulty, but that chassis had been subjected to severe damp at some point, possibly even submerged!

Regards
Lloyd

AdrianH · 30th Nov 2022, 8:20 pm

Just a question on these style of mica's, does the size of them relate to the operating voltage?

Adrian

Andrew2 · 3rd Dec 2022, 9:56 am

Quote:

Originally Posted by AdrianH

Just a question on these style of mica's, does the size of them relate to the operating voltage?

Adrian

I suppose so. To withstand higher voltages the plates have to be spaced further apart, leading to lower capacitance. To make up for this we need more plates (a thicker capacitor) or bigger plates (bigger area).

AdrianH · 3rd Dec 2022, 10:11 am

I have a box of caps in different sizes, no longer any writing on them that can be seen, I can determine their capacitance but not voltage rating?

Adrian

28th Nov 2022, 9:59 pm	#1
Petedox Pentode Join Date: Feb 2020 Location: Waterlooville, Hampshire, UK. Posts: 200	Sticky LEM Silver Mica caps I've replaced a few waxies on my latest project, but was wondering how reliable the above are. They are not quite waxy, more 'sticky'. The first one I checked was fine, but I'd welcome any views - they're not too easy to get at! Attached Thumbnails __________________ Pete BVWS Member

28th Nov 2022, 11:32 pm	#2
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,935	Re: Sticky LEM Silver Mica caps I think they will be fine. The outside of them is a bit sticky and covered in dust, though as long as they are not disturbed mechanically, silvered mica type capacitors are usually very reliable. Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

30th Nov 2022, 4:53 pm	#3
Petedox Pentode Join Date: Feb 2020 Location: Waterlooville, Hampshire, UK. Posts: 200	Re: Sticky LEM Silver Mica caps That helps put my mind at rest. Thanks Christopher. __________________ Pete BVWS Member

30th Nov 2022, 7:34 pm	#4
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,982	Re: Sticky LEM Silver Mica caps I'm looking at some NOS LEMCO 1500pF +/-5% mica on my desk as I type. Exactly the same as in your set, wax coated. They measure just fine - well within tolerance, and low loss on my bridges (note the plural!) So I would say you have nothing to much to worry about with them in your set. Craig __________________ Doomed for a certain term to walk the night

30th Nov 2022, 7:36 pm	#5
Lloyd 1985 Nonode Join Date: Jun 2008 Location: Coningsby, Lincolnshire, UK. Posts: 2,819	Re: Sticky LEM Silver Mica caps I’ve normally found them to be reliable, but a few years ago I was restoring an Ekco A22 and I found both of the 2 on that chassis to be faulty, but that chassis had been subjected to severe damp at some point, possibly even submerged! Regards Lloyd

30th Nov 2022, 8:20 pm	#6
AdrianH Octode Join Date: Mar 2020 Location: Blackburn with Darwen, Lancashire, UK. Posts: 1,572	Re: Sticky LEM Silver Mica caps Just a question on these style of mica's, does the size of them relate to the operating voltage? Adrian __________________ Asking questions and learning, or trying to! Youtube EF91Valve

3rd Dec 2022, 10:11 am	#8
AdrianH Octode Join Date: Mar 2020 Location: Blackburn with Darwen, Lancashire, UK. Posts: 1,572	Re: Sticky LEM Silver Mica caps I have a box of caps in different sizes, no longer any writing on them that can be seen, I can determine their capacitance but not voltage rating? Adrian __________________ Asking questions and learning, or trying to! Youtube EF91Valve