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Old 1st March 2006, 05:05 PM   #1
gjo is offline gjo  India
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Default Question about tube amp power supply caps

Folks

I have a Dynaco ST 70 clone from Welborne Labs, the model V.35, and would like to replace the electrolytic capacitors in the power supply board.

The original unit came with Panasonic 330mfd, 450V caps, and these appear to be quite expensive. I have located affordable snap in electrolytic caps at apexjr, of similar rating and welcome any advice from any of you knowledgeable people out there

Link:http://www.apexjr.com/capacitorsR.html

Thanks

George
Bangalore, India
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Old 1st March 2006, 06:54 PM   #2
anatech is offline anatech  Canada
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Hi George,
Make sure you are not buying NOS. You want brand new stock, fresh. Given how long you will own this amp, good caps are not that expensive.

-Chris
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Old 1st March 2006, 06:59 PM   #3
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$6.17 (5.22 qty 10) is expensive? That's the price at DigiKey.com.

What's wrong with the caps that are in there? Surplus caps may not be any newer.... If you want some, I have 330@400V pulls - you can have'em for postage.
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Old 2nd March 2006, 01:21 AM   #4
gjo is offline gjo  India
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Thanks Chris, I'll check.

Tom:

I saw the price on the Welborne Labs site at $14 a pop, and figured that $84 for six caps was a bit higher than I could afford. The Digiikey option opens up possibilities..

I am looking at replacing them is because when I power off the amp, one channel doesnt retain the audio for more than a second or so, whereas the other channel continues for about 8-10 seconds, leading me to think that there is a problem. Could there be any way for me to check whether the caps need to be replaced, or if the problem lies elsewhere?

Thanks

George
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Old 2nd March 2006, 03:04 AM   #5
anatech is offline anatech  Canada
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Hi George,
This could be caused by low bias current, or turn off transients. I normally look at the waveforms across the caps with a 'scope. If I see big "pips" on the leading edge, the cap may be defective. I measure them to be sure in an unfamiliar amp.

-Chris
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Old 2nd March 2006, 06:52 AM   #6
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Illinois Capacitor, Nichon and Xicon are about the lowest priced and I have had no problem with them in PSU.

Xicon's make great cathode bypass too for their price, though Panasonics do sound better there.
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Old 3rd March 2006, 02:21 PM   #7
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Geek

Do you use electrolytic to bypass? try Silver Mica or MKP

[]s
Joo
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Old 5th March 2006, 01:34 PM   #8
lndm is offline lndm  Australia
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Old computer switchmode power supplies are a good source of HV electro's. Some are sonically good brands. Most (check for expansion) are undamaged and useable within their marked tolerances.
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Old 5th March 2006, 06:07 PM   #9
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Hi,

Quote:
Originally posted by jmartins
Geek

Do you use electrolytic to bypass? try Silver Mica or MKP

I bypass with electrolytic and couple with MKP.

I have tried all sorts of caps in cathodes for bypass. Tantalums are interesting, but not so interesting to warrant $4 over $0.40
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Old 5th March 2006, 07:36 PM   #10
Nordic is offline Nordic  South Africa
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Most of the cheap stuff I can get is Jamicon and Hitano, are those any good?
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