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PS filter caps for Adcom GFA-555
PS filter caps for Adcom GFA-555
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Old 30th August 2008, 06:54 AM   #1
openhacker is offline openhacker  United States
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Default PS filter caps for Adcom GFA-555

The power supply filter caps in my adcom GFA-555 are labeled as 80WVDC They have 77V across them (measured).

The service manual I have lists 81V across them, and 100V parts.

I just had the amp serviced (maybe that was a mistake) -- the tech put it an 80V cap -- when I said the manual said 100V -- he said "I replaced what I took out".

Naturally, it doesn't look anything like the original cap.

So what's the story with this? Were there multiple versoins of the GFA-555?

Isn't 77V across an 80V cap kinda close? (its 100V peak).

I tend to think even though they're labeled as 80V -- they may be higher quality parts and labeled conservatively...(they are also "Adcom" branded.

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Old 30th August 2008, 10:04 AM   #2
djk is offline djk
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This is what I might use for the GFA555, $15 from apexjr.com


'Peak' or 'Surge' ratings on caps are only for choke input filters and either 8.3mS/10mS (60hz/50hz) half cycle.

I have a pile of real GFA555 caps, they are 15,000F at 100V, 2-1/2" dia.

80V caps may work for a while, it's better to have a bit more margin.
Candidates for the Darwin Award should not read this author.
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Old 30th August 2008, 12:30 PM   #3
ostripper is offline ostripper  United States
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Location: Smoky Mountains , Tennessee
Yeah, every 10% a capacitor is derated for any given supply
voltage will double its life . Commercial (Fisher,JVC,etc.)
will use 63v cap for 58VDC, Ive seen them "bleed" after 4-5

I use 100v for ALL my DIY amps 60-70VDC and all my repairs.
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Old 27th September 2008, 01:46 AM   #4
openhacker is offline openhacker  United States
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Join Date: Aug 2008
I filed a complaint at the BBB against the shop for this repair.

I also gave them a user manual and a shop manual -- they couldn't "find" it to give it back to me (I've seen them for sale on ebay).
They agreed to reimburse me for the manuals.

What I don't understand is why the caps are labeled 80V (there
"adcom" capacitors, not a general electronic vendor), the shop guide
lists 100V parts and there's 77V across them (at my house).

The "manager" gave me a **** and bull story about how UL wouldn't let you use "incorrect" parts -- but I have no idea why UL would even care if the caps don't flame out.

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