Help needed on replacing Adcom 545 power supply caps! - diyAudio
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Old 2nd July 2011, 07:47 PM   #1
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Default Help needed on replacing Adcom 545 power supply caps!

Hi all,
Dumb question from a noob; I have a couple of Adcom amps (545 and 535 II) that could only benefit from new electrolytic caps. What's the best way to drain down the caps? I've read about using a resistor, a bulb, etc. How exactly is this done? I know it can be dangerous, both to the gear and the person if you dont know what you are doing and do it wrong. And I dont think i'm that person to try it unsupervised. But my friend and local go to for electronics questions and repairs is out of town indefinitely. And I'd still like to know the proper procedure for doing it for myself. And I'm not totally inexperienced with electronics repair, just not formally trained. Any input would be welcome. Thanks!
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Old 2nd July 2011, 07:52 PM   #2
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Oh...and what are some of the preferred brands? Jensen? Nichicon? I'm not trying to do overkill. I like the amp more or less as is soundwise. But any decent improvements that can be made with minimal invasion and replacement are more than welcome!
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Old 2nd July 2011, 08:35 PM   #3
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Originally Posted by musicallowb View Post


and what are some of the preferred brands?
what brand are the originals?
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Old 2nd July 2011, 11:31 PM   #4
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The originals are Adcom rebranded, 10,000uF/63V (x4). But I believe they are actually by Towa Electron Co. LTD. Because...uh...they actually also say Towa. :-)

Last edited by musicallowb; 2nd July 2011 at 11:37 PM.
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Old 3rd July 2011, 12:17 AM   #5
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What is their diameter? You'll want to find caps that fit right in the clamps/brackets those amps use to hold them in place. What's the rail voltage in the 545?

The caps probably don't hold a charge for long after you turn the amp off. If they do, put a large, 2W or more resistor, to discharge them down to less than 1Vdc. Monitor the voltage across the cap with a DMM.
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Last edited by Stormrider; 3rd July 2011 at 12:23 AM.
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Old 3rd July 2011, 01:15 AM   #6
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Quote:
Originally Posted by musicallowb View Post
The originals are Adcom rebranded, 10,000uF/63V (x4). But I believe they are actually by Towa Electron Co. LTD. Because...uh...they actually also say Towa. :-)
Digikey has epcos and vishay caps in those values. You can also replace those with higher rating such as 15000uf /80v. If you go this route just make sure you replace the bridge rectifiers with higher value.

Last edited by wannabeaudiophile; 3rd July 2011 at 01:26 AM.
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Old 4th July 2011, 03:06 AM   #7
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@ Stormrider, I understand that the rail voltage is about 50v. How do I measure to make sure?...again, new to amp mods. Guitars are so much easier....

@wannabe, thanks for the caps suggestions. I will look into those, too.
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Old 4th July 2011, 03:35 AM   #8
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Connect a DMM across one of the PS caps using clip leads. Keep your hands out of the chassis. Plug the amp in, turn it on, and record voltage reading.

50V sounds right though. I was just wondering how close Adcom speced the voltage rating. 63Vdc caps should be fine.
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Old 4th July 2011, 05:34 AM   #9
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Bridges should already be 25A@ 400V , good for a much larger amp - they are fine. The adcom is one of the only amps built like a DIY one !
No load voltage is about 54-0-54vdc - I have gutted one for a DIY build.


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Old 4th July 2011, 12:04 PM   #10
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Apex jr may have OEM PS caps for this model.

BTW, do a search on bypass caps for the power supply. This is a cheap and simple mod that will give a small improvement (bass is a bit cleaner). In fact some of the series 2 adcoms have this.
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