Gentlemen, saw this discussion today.
I have "lots" of experience with these caps.
You see the red caps with Roe and Siemens logo. I think both were made
in the Roederstrein plant. We used to order these on a regular basis and
when they arrived came as either R. or Siemens 35 years ago.
As said problems start after decades (sometimes one decade only) and in hot
environment. The plastic case (I don't think it is Bakelite ) can not withstand
thermal stress. The point with max. mechanical stress is on the top edge.
Sometimes the cracks are only visible with mag. glasses.
My experience: the absence of cracks does not guarantee proper function
and also a cracked cap may still have full capacitance. These caps will not
likely fail with a short, but:
They (as probably el. caps in general) don't like to be operated with low dc
voltages. A common point of failure is in a special breed of amps where they
are used for emitter ac coupling with only .5 to .6 volts dc. They may become
conductive with still full capacitance when used like this.
Philips caps with thin wrapped blue and light blue shrink cover are always
suspective. Same for old "Frako" with thin light green-yellow cover.
The red Roe caps have been available as bipolar types as stated here elsewhere.
Over decades I have rarely (if ever) seen any failure with these.
I don't replace them all, only the defective ones. For special gear I use NOS
of the same type in order to preserve originality. If you replace these caps in
precious gear with different ones it will loose its resale value. Another reason
is that they are believed to be sonically superior by some designers.
See also http://www.diyaudio.com/forums/parts/211422-help-id-capacitors-my-preamp.html
I have "lots" of experience with these caps.
You see the red caps with Roe and Siemens logo. I think both were made
in the Roederstrein plant. We used to order these on a regular basis and
when they arrived came as either R. or Siemens 35 years ago.
As said problems start after decades (sometimes one decade only) and in hot
environment. The plastic case (I don't think it is Bakelite ) can not withstand
thermal stress. The point with max. mechanical stress is on the top edge.
Sometimes the cracks are only visible with mag. glasses.
My experience: the absence of cracks does not guarantee proper function
and also a cracked cap may still have full capacitance. These caps will not
likely fail with a short, but:
They (as probably el. caps in general) don't like to be operated with low dc
voltages. A common point of failure is in a special breed of amps where they
are used for emitter ac coupling with only .5 to .6 volts dc. They may become
conductive with still full capacitance when used like this.
Philips caps with thin wrapped blue and light blue shrink cover are always
suspective. Same for old "Frako" with thin light green-yellow cover.
The red Roe caps have been available as bipolar types as stated here elsewhere.
The grey and orange caps are of earlier manufacture.
Over decades I have rarely (if ever) seen any failure with these.
I don't replace them all, only the defective ones. For special gear I use NOS
of the same type in order to preserve originality. If you replace these caps in
precious gear with different ones it will loose its resale value. Another reason
is that they are believed to be sonically superior by some designers.
See also http://www.diyaudio.com/forums/parts/211422-help-id-capacitors-my-preamp.html
Last edited:
I don't know: the Siemens always measured marginally but consistently better than the same capacitance/voltage from Roe
I use a home-brewed esr meter. Description here for example:
http://www.diyaudio.com/forums/parts/199046-oldies-but-goodies.html
http://www.diyaudio.com/forums/parts/199046-oldies-but-goodies.html
I have examined some samples in details: at first sight, they look very similar: identical case dimensions (but it could be down to some DIN standard), similar case thermoset material (except for color of course), similar sealing epoxy resin.
However, when you look with less naive and more technical eyes, there are some telling differences: tiny details like the shape of the feet or the transfer-moulding flash are different, which means they come from different moulds.
This doesn't mean they come from different factories: they could have two (or more) sets of machines, and they may even have actively cultivated some minor differences, just to be able to prove that the brands are actually different.
This is not an uncommon practice: look at some Aldi and Lidl products for example.
I still don't know; all I can tell is that the Siemens ones were always somewhat better, but it could result from an end of process screening...
However, when you look with less naive and more technical eyes, there are some telling differences: tiny details like the shape of the feet or the transfer-moulding flash are different, which means they come from different moulds.
This doesn't mean they come from different factories: they could have two (or more) sets of machines, and they may even have actively cultivated some minor differences, just to be able to prove that the brands are actually different.
This is not an uncommon practice: look at some Aldi and Lidl products for example.
I still don't know; all I can tell is that the Siemens ones were always somewhat better, but it could result from an end of process screening...
I've tried Panasonic FC years ago, 'bout '88 if I remember right ...
... whacked 'em in a nice DIY phono-pre I lashed together in my spare time.
The 'new' Bakelites I have stashed for the NEW phono-pre, aren't dried out or cracked at all ...
... tip top & Bristol in fact !
So should be hunky dory ... I recon.
Si.
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