NAD 3020 drivers

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lineup

lineup

Member
Joined 2005
hello fellows
and NAD 3020 lovers

I made this very simpified schematic ( see attachement )
to show the basic function of
Bjoern E creation from 1979 ( soon 30 year old idea, still working good! )
NAD 3020i

It should be noted, that just because they discovered 2+2 = 4 some thousands of years ago,
this does not make this idea less valid in the year 2008.

Same in chess, which I play daily on internet.
A good move played in the 17th century, is not a bad move now.
Because this is the nature of mathematical, logical things.

And all amplifiers obeys by laws of mathematical expressable formulas.
Be it Ohms Law or other elektronical laws ....
This isalso why our Spice Sims works at 99.5%.
They use formulas for electrical physical things & by such nature.

My simplified schematic.
This can make us, hopefully, understand how the NAD 3020 overall idea is.
And it is is a very good audio amp idea, I would say.

regars, lineup
 

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jjanderson

Member
Joined 2008
Problems

Hi i have put in the 4R7 resistors.
Now i want to adjust the bias but i cant find the solder shorts.
In the service manual is written:


1: Remove input signal and load, set impedance switch to 8oms (Reset to 4 ohms when finished).

2:Remove solder short across R455 and R456

3:Connect DMM across P403 (-) and P404 (+)

4:Turn on and adjust R443 for reading of 28mV (+-2mV)DC

5: Repeat, using P405 (+) and P406 (-), adjust R444

Leave Power on for minimum 5 minutes with no signal connected.

Repeat adjustments.

When finished replace soldershorts across R455 and R456.

But i dont know where the solder shorts between R455 and R456 is.
I have a Nad 3020i, anybody have a picture of this solder short?
Thanks
 
Tube_Dude

Tube_Dude

Member
Joined 2002
Re: Problems

jjanderson said:

Now i want to adjust the bias but i cant find the solder shorts.
Click to expand...

Hi

Near the heatsink, there are two small 1 Ohm resistor, is this resistor that is shorted.

Inspect with a multimeter and you will see that instead of 1 Ohm it will measure 0 Ohms.

All you have to do is to remove the solder short of this resistor, adjust bias and short again... :cool:
 
C

Chrisr3521

Member
Joined 2006
i would pull all transistors in that area and check them for shorts ( search google on how to do this, check things systematicly just because you find one faulty component doesnt mean there are no more, you may want to look into a variac or something similar so you dont keep blowing things when you switch on to test it as well.


thanks
chris
 
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