NAD 3020 differences
- Thread starter Mar12
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doctor fuse
Super Member
Apparently there is an error in the circuit design of the original 3020 ("Series 20"). It is called the "Benign Error', because it created more detail at low volumes. Later models "corrected" this error, but apparently some of the euphonic quality was lost in these later models.
The phonostage in most of amps immediately following the original 3020 were very similar if not almost identical.
The phonostage in most of amps immediately following the original 3020 were very similar if not almost identical.
JeffAtchison
New Member
Can someone tell me if this 3020 has been modified? I recently bought it because I love NAD equipment but I've never seen an LED attached to the chassis. It is always on. Thanks, and I hope it's OK that I'm commenting on this thread. 
JeffAtchison
New Member
Thank you Leesonic... are you in the midwest?
JeffAtchison
New Member
and is it normal for the LED to remain lit the entire time?
No, I'm in NJ.
Yes, because it is part of the circuit. I could have elected to use some diodes there to get the voltage drop across the LED. But it looks cooler IMHO lighting up the interior. If you can send pictures of the back with the serial number, I can possibly tell you when I restored it.
Yes, because it is part of the circuit. I could have elected to use some diodes there to get the voltage drop across the LED. But it looks cooler IMHO lighting up the interior. If you can send pictures of the back with the serial number, I can possibly tell you when I restored it.
losthorizon
Well-Known Member
Sorry to hijack this post but
Sorry to hijack this post, but may I ask you a question? I have a Nad 3120 that is working correctly, but as I intend to keep it, do you think it is worth having it recapped.
Kevin Atkins
New Member
If it's still got the original capacitors in it, then yes a recap would likely be beneficial. Of course, it might be a very 'low mileage' example that might also be OK on its original caps - the condition of the interior might give you some clues, particularly the PCB around hot running parts such as the preamp voltage regulators (just to the right of the output stage heatsink towards the rear of the board). These little gems can sound very fine indeed when fitted with fresh, good quality capacitors. I like Panasonic FC / FR which are reasonably priced and yield excellent results, and Wima film caps for the power stage input coupling caps. I'm just listening to a 'second revision' Series 20 unit now, which I've just done the works to, and it sounds fabulous, and it didn't break the bank.
malden
Lunatic Member
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losthorizon
Well-Known Member
thank you for answering my question, what is involved in a restoration?
malden
Lunatic Member
I'm just a hobbyist and fairly new to electronics but have restored about a half a dozen vintage amps so take this for what it's worth. Someone with much more experience will hopefully will chime in.
In a nutshell:
1) Familiarize yourself with the schematic
2) Do a visual inspection of the components
3) Clean all potentiometers and switches
4) Power it up with a dim-bulb tester
5) If no shorts then remove from dim-bulb
6) if you have a cheap pair of speakers and a source, you could do a listening test
7) take measurements per the schematic
8) Try to localize problems
9) Remove and test components, replace as needed
10) Take more measurements per the schematic
11) Inject a 1000Hz signal with the proper voltage
12) Observe wave-forms on oscilloscope
This is what I use:
schematic
multimeter
signal generator
oscilloscope
soldering iron
soldering wick
dim-bulb tester
transistor tester
capacitor tester
resistor chart
8 ohm dummy load
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