Pass Design Adcom - Filter Cap Problem

PreCD · 21st December 2011, 01:00 AM

I have been studying for a couple of days the variety of PS Filter caps to use in my Pass design Adcom GFA-555 amplifier. For one it seems there are not a huge variety of 15000uf 100v caps out there to be had. I have scoured the earth and am leaning toward a Vishay PHR-ST type. $38 a pop.

Max ESR 16 Mohm @ 100hz.
Rated ripple current @ 100hz = 12.3

What have others used for this amp design?

PreCD · 21st December 2011, 11:58 AM

Done and done. Ordered the Vishays from Digikey along with 3.9kOhm 3W Metal Film resistors which reside on the filter caps at this time. Might as well replace those too. I would like to know why those resistors are there as bleeders though..............

Nelson Pass · 21st December 2011, 10:27 PM

For safety. If the rail fuses are blown, high voltage can sit on those caps
long enough to zap a technician.

Apex Jr · 21st December 2011, 10:45 PM

I have been selling the 22,000Uf 100V caps as replacements

http://www.apexjr.com/images/AdcomCap.jpg

There $23.95ea and have 23 left in stock

Steve @ Apex Jr

PreCD · 21st December 2011, 11:44 PM

Quote:

Originally Posted by Nelson Pass

For safety. If the rail fuses are blown, high voltage can sit on those caps
long enough to zap a technician.

Thank you sir for the kind advice, it is very appreciated. I am trying to quieten the big cat so no blown rail fuses. I will gator clip a 100K 2W resistor between them for awhile and leave it there as I work ok.

Happy Holidays and thanks again.

PreCD · 22nd December 2011, 04:14 PM

Would you bring the amp up with a dim bulb tester after all 4 filter caps are replaced or just put your foot on the gas.

Zen Mod · 22nd December 2011, 04:29 PM

if you are sure in your work - just put foot on the gas

if you have doubts in your work , use bulb safety thingie

PreCD · 22nd December 2011, 04:38 PM

Quote:

Originally Posted by Zen Mod

if you are sure in your work - just put foot on the gas

if you have doubts in your work , use bulb safety thingie

Looks like I will just straighten my knee on the gas pedal then...........

Andersonix · 23rd December 2011, 12:06 AM

Rather than just switch on the amp after working on the PS, you should remove the rail fuses between the PS and amp circuit, and check the PS alone. This way you'll only blow the PS and not the amp if something's wrong.

PreCD · 23rd December 2011, 11:53 AM

Quote:

Originally Posted by Andersonix

Rather than just switch on the amp after working on the PS, you should remove the rail fuses between the PS and amp circuit, and check the PS alone. This way you'll only blow the PS and not the amp if something's wrong.

Good sound advice.

21st December 2011, 01:00 AM	#1
PreCD diyAudio Member Join Date: Sep 2011 Location: USA	Pass Design Adcom - Filter Cap Problem I have been studying for a couple of days the variety of PS Filter caps to use in my Pass design Adcom GFA-555 amplifier. For one it seems there are not a huge variety of 15000uf 100v caps out there to be had. I have scoured the earth and am leaning toward a Vishay PHR-ST type. $38 a pop. Max ESR 16 Mohm @ 100hz. Rated ripple current @ 100hz = 12.3 What have others used for this amp design?

22nd December 2011, 04:29 PM	#7
Zen Mod diyAudio Member Join Date: Jan 2003 Location: ancient Batsch , behind Iron Curtain	if you are sure in your work - just put foot on the gas if you have doubts in your work , use bulb safety thingie __________________ my Papa is smarter than your Nelson ! tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; BAF Forum & Gallery;I'm dumb

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21st December 2011, 11:58 AM	#2
PreCD diyAudio Member Join Date: Sep 2011 Location: USA	Done and done. Ordered the Vishays from Digikey along with 3.9kOhm 3W Metal Film resistors which reside on the filter caps at this time. Might as well replace those too. I would like to know why those resistors are there as bleeders though..............

21st December 2011, 10:27 PM	#3
Nelson Pass The one and only Join Date: Mar 2001	For safety. If the rail fuses are blown, high voltage can sit on those caps long enough to zap a technician.

21st December 2011, 10:45 PM	#4
Apex Jr diyAudio Member Join Date: Jun 2002 Location: Torrance, Calif	I have been selling the 22,000Uf 100V caps as replacements http://www.apexjr.com/images/AdcomCap.jpg There $23.95ea and have 23 left in stock Steve @ Apex Jr

22nd December 2011, 04:14 PM	#6
PreCD diyAudio Member Join Date: Sep 2011 Location: USA	Would you bring the amp up with a dim bulb tester after all 4 filter caps are replaced or just put your foot on the gas.

23rd December 2011, 12:06 AM	#9
Andersonix diyAudio Member Join Date: Jan 2004 Location: Silicon Valley	Rather than just switch on the amp after working on the PS, you should remove the rail fuses between the PS and amp circuit, and check the PS alone. This way you'll only blow the PS and not the amp if something's wrong.

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