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Power supply cap mod
Power supply cap mod
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Old 1st July 2012, 10:09 PM   #1
Kuroje is offline Kuroje  Croatia
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Default Power supply cap mod

I have a PA amplifier 2x450w @8ohms (a crest CA - 9 copy) , it has a big toroidal transformer and 4 x 15000uF 63 v capacitors in its power supply , since this is a 2 step H class amplifier it uses 2 rails and upper one is around 100v ,so these four capacitors must be connected in series to handle the 100v rail ?

Click the image to open in full size.

power supply PCB has 4 free spaces for capacitors (probably designed for the more powerful model)

Click the image to open in full size.

i have 4 15000uF 63v capacitors ,is it possible to install them (i dont have any schematics),and are there any performance gains from this ?
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Old 6th July 2012, 12:19 AM   #2
DCPreamp is offline DCPreamp  United States
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I think you're right about the filter caps. The amp rails are probably +/-50V and +/-100V using two 63V caps, in series, per channel.

Pull the filter-cap PCB and inspect the capacitor locations. If all the empty cap locations are simply paralleled with the existing four caps, then you could simply add your caps. But if the circuitry is separate, uses separate rectifiers, separate transformer windings, etc., then I would recommend against it. If you really want to use your caps (I'm a DIY'er, so I know how hard it is to leave something stock!), and the empty cap locations require extra circuitry, you could use an X-Acto blade, cut the traces isolating the missing cap locations, add the new caps, and add jumpers from the existing caps to the new caps. Before you apply power, double check all your work. Next, apply power without the amp modules connected and measure the voltages. They'll be higher than normal without a load from the amps, but should be reasonable +/- as expected. Lastly, connect the modules and test the whole amp.

Standard warnings apply: Use extreme caution with such high voltages and large caps. If you're not 100% comfortable with doing this, don't do it. If you have a Variac, use it to check the amp bringing up the supply slowly.

Does the amp work okay as it is? If the amp is designed well, then the extra caps won't give you any obvious audible benefits. I see the amp is disassembled in the last pic, so is it damaged?

Enjoy your amp! It looks like a monster and would make a beast of a sub-amp!
"Believers cling to the myth despite the evidence, reinterpret the myth to suit the evidence, or lie about the evidence to support the myth." "To err is human; to blame errors on external factors is even more so."
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Old 6th July 2012, 09:48 PM   #3
Kuroje is offline Kuroje  Croatia
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Join Date: Sep 2011
original CA-9 design uses 8 caps ,and it looks like these empty slots are just parallel conections to original caps

amp had some problems with oscilation or right ch. and this has been resolved
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