Hi - I want to replace these ageing caps in my tube preamp
- not sure of the values - 1 of them says '100M + 100M' and the other 2 say '32M + 32M' - any ideas ???
Well that's an interesting one. This is what I think...
mF would be millifarad (and it is mF and not MF) but if they were in millifarad's then the results would be non sensical. 100mF would be 100,000uF which ain't possible given the physical size and voltage rating.
So I'm going to suggest they 100uF and 32uF. The three legged cans mean 100 + 100 and 32 + 32 (we assume uF) in a shared can. Multiple type caps were very common in TV service years ago, sometimes with three or four different values in one can and sharing a common negative.
I think you will struggle to find replacements for shared can types tbh.
mF would be millifarad (and it is mF and not MF) but if they were in millifarad's then the results would be non sensical. 100mF would be 100,000uF which ain't possible given the physical size and voltage rating.
So I'm going to suggest they 100uF and 32uF. The three legged cans mean 100 + 100 and 32 + 32 (we assume uF) in a shared can. Multiple type caps were very common in TV service years ago, sometimes with three or four different values in one can and sharing a common negative.
I think you will struggle to find replacements for shared can types tbh.
I think they are a reputable company from the Czech republic. They produce valves as well. I have them. They work well. I agree that M for micro is not a standard, but I have seen this before. They do use uF in their technical data though.
They don’t seem to be that old. Why replace them? It would be good to decipher the datecode first.
If you decide to just do something you probably will have to replace them by the same brand and type as shared can types are pretty rare.
https://www.jj-electronic.com/images/stories/product/capacitors/TC_TE_EN_web.pdf
BTW if you don’t have enough experience it may become a disappointing endeavour. You should be familiar with electronics and electrical safety.
If you decide to just do something you probably will have to replace them by the same brand and type as shared can types are pretty rare.
https://www.jj-electronic.com/images/stories/product/capacitors/TC_TE_EN_web.pdf
BTW if you don’t have enough experience it may become a disappointing endeavour. You should be familiar with electronics and electrical safety.
Last edited:
You need to read it as (32 mega)-picofarad = 32 10⁶ 10^-12 = 32 µF. Has been done before for small values.
It's quite simple in fact if you have similar new capacitors for the replacement, but first you have to determine if there's anything wrong with the "old" ones.
Sorry - I'm not making myself very clear ! I want to upgrade these 3 capacitors to superior ones - is it possible to replace dual capacitors with normal 'single' caps - there is plenty of space in the preamp to do this
Highly irregular to do so. No plain wrong even 🙂 So 1 kilo milli Ampere would then be 1 A. Crazy!
Probably it is just m for micro and not following ISO.
These are very commonly used in guitar and bass amplifiers. In this case, M is microfarad. They are not the best, but they aren't the worst, for sure. There aren't a lot of multi section can cap options out there, but a better quality, IMO, would be F&T. I've used them for a lot of guitar amp projects and they test and perform well. CE Manufacturing also makes the old style Mallory can caps, but they are quite expensive in comparison. Check out Antique Electronic Supply for options.
And yes, if you have room for single caps, good ones can exceed the quality of multi section caps. I prefer single-section caps in my guitar amps and use multi section only for repairs and servicing of amps that require multi section caps, or in the few I've built that have no room for multiple single section caps.
And yes, if you have room for single caps, good ones can exceed the quality of multi section caps. I prefer single-section caps in my guitar amps and use multi section only for repairs and servicing of amps that require multi section caps, or in the few I've built that have no room for multiple single section caps.
Thanks - for example - if I wanted to replace the 100uF+ 100uF double cap with superior quality would I need 2 single caps in parallel, both 50uF or both 100uF ?
If you ask that you better not do anything. Sorry.
Multiple section capacitors are seldom wired in parallel. Mostly they are used as separate capacitors with the negative grounded.
They were originally made to save space and reduce cost in TV sets. Your parts are dual section 500V, some 100uF, some 32uF.
Non of the above 😉
You need two 100uF with the negative of each connected together. That becomes the common - connection.