swapping caps in an old SMPS

Eldam

Banned
2012-09-13 12:25 am
France
Hello,

I have a 20 years old SPM 1000 B Chord amp ! Maybe time to check the SMPS caps and the amps boards ones as well !

In case of rebranded caps at the name of Chord Audio company (not open the amp yet) what are the best tecnichal factors please for new caps in a smps if genuine caps are out of stocks today:

- very low impedance ?
- Long Life ? 125° e.g.
- Some better than others ? Rifa ? Siemens Sicorel, others ?

Thanks in advance

regards
 

Eldam

Banned
2012-09-13 12:25 am
France
Thanks Abrax, nice to see you :)!

No I don't forgett low ESR as a good choice, but believed just in the smoothing position aera it was maybe not the best place for them as current is always and rapidly already change of sense (AC smoothing I mean)? Btw if I remember Siemens Sicorel has very good ESR (have to check for sure the datasheet and sizes !)

Thanks for the tip, as I don't like too much the Nichicons (often a little curtained, but the KZ...)!
Ok I will have a look at Nippon Chemicon ! Like Panasonic FC often as well (much more than the FM and FK series), but not as good despite close ESR between them ! (Strange experiments I did last years : non logical results I mean : results where more different about voltage ratting than ESR !!!! But it was not about fast SMPS but just in a DAC supply !)
Thanks again !
 
Thanks for the welcome Eldam :)

Low ESR is good for not just audio reasons - with lower ESR the cap should run cooler and hence live longer.

But there is a gotcha there - cap ESR seems (from my measurements) to be a strong function of temperature. I notice this effect when I've a cap in my hand, connected to the LCR meter. As it warms up, its ESR goes down. I don't know if there's a temperature this effect stops at, or even if there's a turn-around, but between room temperature and body heat, a cap's ESR can easily halve (on a cold day in my apartment, mind).

So on one hand we want caps to last, hence we run them cool. But they work best when warm. Catch 22 :D
 

infinia

Member
2005-05-15 9:51 am
SoCal
well I suspect caps in a SMPS power filter may perhaps like batteries (chemistry) work better when warmer but at the expense of shorter lifetime. remember SMPS uses some feedback stability networks that account for ESR so don't stray too far.
replacement Caps 1st select by fit form function then brands / price. not in reverse LOL you should see improvements in ESR just due to advancements in Tech over the time from the repaired products advanced age.
 
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Eldam

Banned
2012-09-13 12:25 am
France
Thanks Infinia,

So an impedance the closest to the original caps...

ok no tweaks with said better spec caps, just good brand, e.g. Nippon Chemicon with close specs in ESR and of course capacitance (will check the % of precision) & voltage !

I surmised SMPS was a strange beast, at least to me :soapbox: , understanding above my head !:scratch1:
 

infinia

Member
2005-05-15 9:51 am
SoCal
ok no tweaks with said better spec caps, just good brand, e.g. Nippon Chemicon:

strangely you mention it, I often come up with this brand after all my criteria is examined.
the caps heat from being in enclosed spaces with power devices not self heating (ESR)is the dominate lifetime factors.
case size has some merits as well.
 
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Eldam

Banned
2012-09-13 12:25 am
France
Some choice at Nippon Chemicon : http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-sepa-e/001-guide/al-groupchart-e-150701.pdf#page=2

for instance : http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-sepa-e/004-lead/al-kzn-e-150701.pdf

Of course they have like all the brands an Audio serie with a poor datasheet :eek: : http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-sepa-e/007-audio/al-ajlug-e-150701.pdf

Panasonic FR has also impressive datasheet ! Although Panasonic FC gives often better result than FM or FR despite lower spec ! :scratch1: (Pan FC + Jamicon worked well in my old Nad monitor serie, better than the genuine ones, but of course no SMPS here !)

http://www.ttieurope.com/attach/18893 (Panasonic FR)

Yageo ?

Importance of Tang loss according to you ?
 
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infinia

Member
2005-05-15 9:51 am
SoCal
I find size lead spacing 1st , 2ndly voltage rating.
then sort by available in stock > lastly temperatures , esr , price etc
they have better series for SMPS! the series you mention for "audio" or FM FC are not ideal for bypass and/ or SMPS.
note > EXACT capacitance isn't that important for bypass uses , within ballpark value, max voltage and case size the lowest ESR at higher frequencies ~100KHz are best! because sorting like I do, often you will find capacitance has increased for new bypass "value" type replacement parts.
 
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