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Old 16th March 2006, 05:07 PM   #1
sberube is offline sberube  United States
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Default power supply capacitor upgrade on Quad 405-2

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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Old 18th March 2006, 02:40 AM   #2
anatech is offline anatech  Canada
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Hi Sebastien,
The 12K caps are within tolerance, don't worry about putting them in. You start running into trouble when you take big steps up in capacitance.

-Chris
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Old 18th March 2006, 05:09 PM   #3
sberube is offline sberube  United States
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Thanks alot Anatech. I'll try it next week then
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Old 19th March 2006, 12:46 PM   #4
ary is offline ary  China
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Default OK

Yes it's all right
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Old 21st March 2006, 01:51 PM   #5
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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
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Old 22nd March 2006, 10:51 AM   #6
DRC is offline DRC  United Kingdom
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Be sure to get high temperature caps for long life !!
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Old 22nd March 2006, 11:10 AM   #7
forr is offline forr  France
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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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Old 22nd March 2006, 11:23 AM   #8
AndrewT is online now AndrewT  Scotland
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Hi,
mirroring Drc's post, I would go for increased temperature rating rather than increased voltage.

Although 50Vdc just works an increase to 63Vdc and 105degC may pay dividends in the long term.

Now it's finding a package that matches the foortprint.
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regards Andrew T.
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Old 22nd March 2006, 11:57 AM   #9
sberube is offline sberube  United States
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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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Old 23rd March 2006, 12:14 AM   #10
anatech is offline anatech  Canada
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Hi Sebastien,
Fresh new are better than brand name old. Just buy a good brand that's long in the industry. What choices do you have?

BTW, I am root too, but never log in that way.

-Chris
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