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Old 21st January 2017, 04:52 PM   #1
blrh93 is offline blrh93  United Kingdom
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Default nad 3020b cap replacement problem

hi, i have a nad 3020b amp it recently developed a buzzing

i had a look inside and a few of the caps where bulging on the top

so i decided to replace 6 caps in total

here is what i replaced the originals with

Click the image to open in full size.

and main psu caps

Click the image to open in full size.


so after getting it back together, it has fixed the constant buzzin, but over around 1/3 volume the amp develops a noise that sounds like a record scratching, this starts with the bass

have i used the wrong tye of capacitors? i made sure to replace with the same voltage and capacitance ratings

any help appreciated

regards Ben
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Old 21st January 2017, 05:29 PM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by blrh93 View Post
over around 1/3 volume the amp develops a noise that sounds like a record scratching,
this starts with the bass
Do you have a meter for checking voltage?
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Old 21st January 2017, 07:01 PM   #3
blrh93 is offline blrh93  United Kingdom
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i have a multi meter, what should i check?
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Old 21st January 2017, 08:01 PM   #4
rayma is offline rayma  United States
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Originally Posted by blrh93 View Post
i have a multi meter, what should i check?
Ok, set it to DCV. If not autoranging, set it to an over 40V range.
Connect the black lead to chassis ground and use the red lead to check voltages of -

1] red speaker outputs of both channels, for 0VDC.
2] main power supply voltages, both positive and negative, for 28VDC on either.
3] regulated voltages, both positive and negative, for 25.8VDC on either.
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Old 22nd January 2017, 09:15 AM   #5
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Hi!
I experienced similar issue, some caps should not have too low esr in 3020 model, especially those small ones, try solder back old caps, and try the sound after recaping again every single cap.
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Old 22nd January 2017, 10:22 AM   #6
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Best tip: buy industrial quality caps from a real distributor so you can be assured you buy the real thing. I would not use Sancon if I was given them for free.
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Old 22nd January 2017, 01:50 PM   #7
Welcome is offline Welcome  France
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Indeed, it looks like you've used essentially fake caps. Those things might not work as intended. I recommend using the originals instead of those things.
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Old 22nd January 2017, 06:56 PM   #8
blrh93 is offline blrh93  United Kingdom
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what brands should i look for? are the nichicon ones ok?
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Old 22nd January 2017, 06:57 PM   #9
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If you buy them from a distributor then: Yes.
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Old 22nd January 2017, 08:25 PM   #10
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Quote:
Originally Posted by blrh93 View Post
what brands should i look for? are the nichicon ones ok?
I had the problems using original Nichicon FGs as C615, 616, 625, 626 https://www.elektrotanya.com/nad_302.../download.html because the amp started to act like motorbike engine, and had back to factory mounted, then the amp began behavior like it should.

My guess was that they had too low esr...

All other caps you might to exchange with any you like but those four are enginestarter
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