|
Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets. |
|
Thread Tools |
25th Oct 2019, 10:58 pm | #1 |
Rest in Peace
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
|
'MicaMold' capacitors
'MicaMould' capacitors: I'm sure many of us have seen them. They're usually in big metal cases, chassis mount, non-polarised, often with screw connections. Capacitances are typically 1 to 20 uF; working voltages can typically range from 300 to 1500 v.d.c.; similar for a.c. voltage ratings.
So question: is there any demand for these capacitors these days? I have a large quantity (various C and V) that I doubt I'll ever use. Al. |
25th Oct 2019, 11:15 pm | #2 |
No Longer a Member
Join Date: Oct 2016
Location: Maroochydore, Queensland, Australia.
Posts: 2,679
|
Re: 'MicaMould' capacitors
I think there could still be some demand for them. I have found that these physically larger high voltage types are much more reliable than their smaller molded counterparts, less often short out. Mostly these types of caps were deployed as RF bypasses or antenna coupling capacitors etc. They could still be of use to those interested in making high voltage power supplies, like the Tesla coil enthusiasts.
|
26th Oct 2019, 12:43 pm | #3 |
Nonode
Join Date: Jun 2007
Location: Coulsdon, London, UK.
Posts: 2,169
|
Re: 'MicaMould' capacitors
The Micamold capacitors that I have encountered are the paper insulated ones encased in a molded bakelite case.
They are leaky and best replaced if you want a working radio. Fine for a museum. |
26th Oct 2019, 1:16 pm | #4 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,203
|
Re: 'MicaMould' capacitors
Micamold up to a few nF are really mica, larger ones are all paper as far as I know. I've never heard of ones in metal cans. Those might be slightly more reliable, though you might not want to depend on them where failure can cause damage.
|
26th Oct 2019, 2:16 pm | #5 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,099
|
Re: 'MicaMould' capacitors
My understanding is that this type of capacitor were meant to be substitutes for mica capacitors. Their origin is the USA during WW2 when there was a shortage of mica.
I do not know what they are made of but they behave like paper because they are invariably leaky. So maybe they are (usually) low value paper capacitors where the paper stood in for mica. |
26th Oct 2019, 3:32 pm | #6 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
|
Re: 'MicaMold' capacitors
According to a post here: https://www.antiqueradios.com/forums...ic.php?t=34265
the smaller ones may be mica, but the larger ones are paper, and therefore suspect. It's a brand rather than a technology. |
26th Oct 2019, 3:59 pm | #7 |
Dekatron
Join Date: Aug 2003
Location: near Reading (and sometimes Torquay)
Posts: 3,099
|
Re: 'MicaMold' capacitors
My information is based on their actual advert of the period (but I can't remember where I saw it). They explained how they were saving precious US mica resources by making these substitute capacitors. I think the brand was created for this purpose - but may have lived on after the war.
|