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Old 5th February 2008, 02:57 PM   #1
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Unhappy NAD C300 schematic and/or help...

Since a long time I have a NAD C300 amplifier and I really liked it. It's simple, does (or must I say... Did) what it has to do and sounds pretty good.
But now, he's dead. It happened about a year ago when a leaking roof spilled some water into the PCB. First I heard a noise, like an overdriven sound, then the red LED lit up, what means the amp goes into 'protect mode' and then it failed completely. The two big (5A) fuses were blown and they immediately blow again when the amp is powered. When the PSU is disconnected, they don't blow so it is a short circuit in the main PCB, not in the PSU itsself.
I checked several Big SS-components for short circuits (still soldered on the PCB) and the two big 10.000F Capacitors but I couldn't find a short.
Does any one have a schematic of this amplifier. I allready tried several NAD dealers and repair shops but I think they don't like to give away this information.
Without a schematic it's really hard to start looking because a lot of components were used in this amp and the faulty one(s) could be everyware...

Grtz J
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Old 9th February 2008, 07:59 PM   #2
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Nobody??
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Old 9th February 2008, 11:22 PM   #3
Bigred is offline Bigred  Canada
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I'd guess that the mosfets are damaged. Wish I could help on the manual but no luck. Maybe try NAD directly for the service info.
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Old 10th February 2008, 11:49 AM   #4
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Default C300 new acoustic dimension

I have a pdf-servicemanual.

What's your emailadress?

regards mike the pike
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Old 11th February 2008, 06:23 AM   #5
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Hi mike, a manual would be very nice!!
Because I'm new here, I can't send you messages so here my email adress: (back to front)
s o a p w a t e r AT h o t m a i l DOT c o m

m o c TOD l i a m t o h TA r e t a w p a o s

Thanks very, very much!!

J
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Old 11th February 2008, 11:41 AM   #6
Quattor is offline Quattor  France
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If it's not too much trouble for you, could you please send me a service manual as well? Thank you very much. The address is:

gospodarlutaka(monkey)gmail(dot)com
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Old 22nd March 2010, 12:38 PM   #7
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Quote:
Originally Posted by derguteton View Post
I have a pdf-servicemanual.

What's your emailadress?

regards mike the pike
Hi Mark,

would you please send me the NAD C300 service manual, I am looking for a replacement of its transformer (ringkerntrafo), which is damaged a few days ago, and so that I can't measure the output voltage anymore.

pir8erxxl@hotmail.com

Regards!
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Old 22nd March 2010, 04:36 PM   #8
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Hi pir8erxxl,

At 6 pin connector CZ703/CB703 you should have this voltage:

- pin #1 = +37VDC
- pin #2 = GND
- pin #3 = -37VDC
- pin #4 = +32VDC
- pin #5 = -32VDC
- pin #6 = GND

From these DC voltages you should be able to calculate AC voltages at transformer secondaries...and don't forget to count in voltage drop over diode bridges ;-)
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Old 23rd March 2010, 01:30 PM   #9
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Quote:
Originally Posted by aparatusonitus View Post
Hi pir8erxxl,

At 6 pin connector CZ703/CB703 you should have this voltage:

- pin #1 = +37VDC
- pin #2 = GND
- pin #3 = -37VDC
- pin #4 = +32VDC
- pin #5 = -32VDC
- pin #6 = GND

From these DC voltages you should be able to calculate AC voltages at transformer secondaries...and don't forget to count in voltage drop over diode bridges ;-)
Thanks alot!

That is what I am exactly looking for!
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Old 23rd March 2010, 09:29 PM   #10
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trafo of this amp ...nightmare !!!!
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