Help Identifying Wax Cap - UK Vintage Radio Repair and Restoration Discussion Forum

sotatech · 2nd Aug 2021, 5:20 pm

I wonder could someone identify the value of the attached wax capacitor please. It is marked L.E.M. and 270 (R?) but it a bit smudged.

Thanks!

paulsherwin · 2nd Aug 2021, 5:23 pm

Looks like a 270pF mica to me. Unlikely to be bad.

dazzlevision · 2nd Aug 2021, 7:59 pm

Quote:

Originally Posted by paulsherwin

Looks like a 270pF mica to me. Unlikely to be bad.

Yes, I agree.

L.E.M. = The London Electrical Manufacturing Company Ltd.

sotatech · 4th Aug 2021, 8:39 am

OK, thanks guys. It looks like a wax cap as the coating has a little give in it and I can scrape a bit of it off with a screwdriver.

DMcMahon · 4th Aug 2021, 9:59 am

Often early Mica capacitors were encapsulated in wax, not to be confused with paper capacitors with a wax coating which are often referred to as waxey's.

David

Lucien Nunes · 4th Aug 2021, 12:07 pm

This is an important distinction. When we refer to 'waxies' it is specifically the wax-coated paper capacitors that are invariably leaky. The problem is that the paper is hygroscopic and in the absence of hermetic sealing it absorbs water over time (although more recent studies suggest that some water may also be produced by decomposition of the paper.)

Mica capacitors are not hygroscopic therefore the choice of encapsulation, whether a resin moulding, dip or wax does not make much of a difference to their lifespan, so the presence of wax on a mica cap is not cause for concern and the capacitor is likely to be as good as new.

2nd Aug 2021, 5:20 pm	#1
sotatech Diode Join Date: Jul 2021 Location: Galway, County Galway, Ireland. Posts: 4	Help Identifying Wax Cap I wonder could someone identify the value of the attached wax capacitor please. It is marked L.E.M. and 270 (R?) but it a bit smudged. Thanks! Attached Thumbnails

2nd Aug 2021, 5:23 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Help Identifying Wax Cap Looks like a 270pF mica to me. Unlikely to be bad.

4th Aug 2021, 8:39 am	#4
sotatech Diode Join Date: Jul 2021 Location: Galway, County Galway, Ireland. Posts: 4	Re: Help Identifying Wax Cap OK, thanks guys. It looks like a wax cap as the coating has a little give in it and I can scrape a bit of it off with a screwdriver.

4th Aug 2021, 9:59 am	#5
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Help Identifying Wax Cap Often early Mica capacitors were encapsulated in wax, not to be confused with paper capacitors with a wax coating which are often referred to as waxey's. David

4th Aug 2021, 12:07 pm	#6
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Help Identifying Wax Cap This is an important distinction. When we refer to 'waxies' it is specifically the wax-coated paper capacitors that are invariably leaky. The problem is that the paper is hygroscopic and in the absence of hermetic sealing it absorbs water over time (although more recent studies suggest that some water may also be produced by decomposition of the paper.) Mica capacitors are not hygroscopic therefore the choice of encapsulation, whether a resin moulding, dip or wax does not make much of a difference to their lifespan, so the presence of wax on a mica cap is not cause for concern and the capacitor is likely to be as good as new.