power supply capacitor upgrade on Quad 405-2

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sberube

Member
Joined 2004
Hi all,

I'm currently contemplating a replacement of my Quad 405-2's power supply capacitors (original ~20 year old electrolytic caps). Now the current values are 10k uf at 50v. I'm thinking to stick a higher voltage cap (63 or 80V) and I've just noticed that I could actually get 12k uf at 80v caps from my local retailer (SMH ELECTROLYTICs). Could replacing 10k uf caps by 12k uf ones be detrimental in any ways? Or is it just going to provide the circuit with a more stable source of current?

Any comments are very much welcome before I blow up my PA :)
 
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jacques54

Member
Joined 2005
Hello Sebastien,

If you google somewhat, you will find that the power supply capacitors have been replaced with 12000 uF up to 22000 uF values. The rectifier bridge, a 7A PM7A2Q, seems to be able to cope with them.
I have put two 22000 uF/63V (EPCOS) in a 405 because they fitted nicely in the clamps (50mm diameter, 80mm height). I still need to find some time to upgrade the modules themselves.

Cheers,

Jacques
 
forr

forr

Member
Joined 2004
Having measured the tan-delta of a lot of electrolytic capacitors, I have been surprised that how almost all of them, even the old ones, behave correctly from this point of view. Then I wonder if it is worth to change the reservoir capacitors of an amp without knowing their real state.
 
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sberube

Member
Joined 2004
Thanks for all the great info... The only caps I can find around here are rated 85 celcius (LPO and SHM).

As for checking for capacitance prior to replacing the caps, I just won't bother give the price of the caps... I'll end up paying at most 10$ per cap for the replacement units (12000 uF 63 or 80V).

Now would anybody recommend one brand over the other?
 
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sberube

Member
Joined 2004
Well, I'm from montreal, so my source for componants is baiscally solen (www.solen.ca). They carry many brands of caps, but the only two brands that will actually provide me with the specs I need are the LPO by ELNA and the SHM by UCC.

Suggestions?

And no, I never login directly as root :) I've been in the business of "being root" for over 12 years... :)
 
A

AndrewT

R.I.P.
Joined 2004
Hi,
if the 405 runs both channels off one set of single rectifier and one pair of 12mF caps, then you may get a boost in performance by duplicating the PSU from rectifier onwards.
so instead of 12mF+12mF would become 15mF times 4.

The difficult part would be packaging it to fit inside the case.
 
S

sberube

Member
Joined 2004
Wow, lots of very good advice. Thanks to you all. I'll start by going 12 or 15mf at 63V and see what that will give me. (given the pricetag of 5-10$ per cap, its a cheap experiment). Then I'll definately consider going with the double mono setup.

I've read alot of comments on upgrading the 405s and will most probably start with the PSU caps, the RCA plugs (I've already done it but in a very bad way with very bad component which I'll fix up properly) and change the caps on the amps. I also want to replace the opamps, but I'm just not that good with a soldering iron :) I'll probably get that done later.

Has anybody changed the resistances to accomodate 1.5v source?
 
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