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NAD Series 20 3020 missing AMP Circuit!?!?

freetoad

freetoad

New Member
Hello all!

I'm pretty new to Hi-Fi and I picked up what I thout was a great deal on a NAD 3020 for only 25$ I got home and popped it open, I was dismayed to discover that the amp looked completely different on the inside compaired to photos ive seen online here and in other forums.

Can you look at this,and verify... is my amp actually missing?! Is there a parts list so that I can recreate the missing section?

Why would someone do this to an amplifier.

The lady who sold it said it was her dad's, way back when. it was part of his setup..
http://audiokarma.org/forums/index.php?media/wp_20151106_13_20_11_pro-2.5320/
http://audiokarma.org/forums/index.php?media/wp_20151106_13_20_40_pro.5321/
 
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I wonder if it was used as a pre amp?

I suggest you message Leesonic about a new amp section. He knows these amps very well.
 
looks like amp is there and just missing the heat sink and power transistors .. maybe you could find another heat sink and transistors to fit ..
p.s what country are you in ?
 
Yes, its the wierdest thing. It looks like there are four large and two small transistors all attached to the heat sync. I assume these are for Power regulation or the Power Amp, since she said it was in her Dad's set up, could he have just been using the preamp section, or just the Phono? and if so, does it make sense to take those larger transistors out?

I am in the US of America
 
the smaller transistors would be likely for bias tracking ..
it maybe had blown outputs and was in the middle of repairing it ..and in the meantime using as a preamp ..
i would contact whoever you got it from and see if the parts are there .
 
Judging by the appearance, I would guess it started life as an integrated amp, something went wrong, and they just pulled the output transistors and driver transistors. The large transformer and four capacitors nearby confirm it was an integrated and not a preamp from the factory.

From the top of my head, you'll need

2 x 2N3055
2 x MJ2995
2 x BD139
2 x BD237
2 x BD238
Plus a heatsink for the outputs.

It would seem a shame to put all new output transistors and whatnot, and not recap the rest of it. Those capacitors are around 35 years old now.

Lee.
 
Was it sold as working and/or did you test it at all? I assume not or you and the seller would have noticed right off that there was not output. :D Good idea to always test a piece of gear and see if it works rather than assuming. People seem nice and they think they know what's what with a piece of gear, and then you end up with this. :dunno:
 
@ Toxcrusadr - i did test it somewhat. When turned up very loud i got some cracling representation of the audio, I knew something was wrong, but hopeing it was somthing simple i talked her down from 100 to 25 $ - i figured its worth the parts at that point.

@ leesonic - is this where the parts go?
NADY.jpg
 
@ leesonic - is this where the parts go?
View attachment 645927[/QUOTE]

That looks about right. I can't check right now as I'm using a tablet with no access to the schematics or parts lists on my computer.

$25 is well worth it for parts alone. You probably won't have to spend that just for the transistors, but it will cost a lot more for all the caps, but well worth doing.

The only hard part is the heatsink. It is possible to drill your own using a piece of L-shaped aluminium. Check out threads started by me in the solid state forum, although the pictures may no longer be there thanks to Comcast shutting down personal webpage space.

Lee.
 
Have a look at this thread :

http://audiokarma.org/forums/index.php?threads/another-nad-3020-rebuild-and-upgrade.534006/

I just updated the picture links for the heatsink I made.

I would strongly advise fixing your amp up the right way. Even if you replace the transistors, it would be sounding it's best, and may have problems later on due to the old caps. Do the right thing and freshen the whole thing up, you won't be disapointed with the sound.

Lee.
 
Holy Cow, that is an awesome job you did on the old girl. I'm going to perform the same type of upgrade. If you have the schismatics or a diagram that you could forward me that would be awesome.
 
You'll find the schematics and service manual on the usual suspect web sites like hifiengine and hifi-manuals.

Lee.
 
do you think it would be OK to use thermal glue on TOP of the large transistors,then plop a heatsink down onto that? then screw small heat sinks to the smaller transistors.
 
If it works as a preamp, I'd just leave it that way. It's only 20 wpc. Get a 2200PE, or something else with real power.
 
freetoad said:
do you think it would be OK to use thermal glue on TOP of the large transistors,then plop a heatsink down onto that? then screw small heat sinks to the smaller transistors.
Click to expand...
not a good idea at all .. just use something similar to original ..its not hard to do .
 
freetoad said:
do you think it would be OK to use thermal glue on TOP of the large transistors,then plop a heatsink down onto that? then screw small heat sinks to the smaller transistors.
Click to expand...

No. The base contact area is where all the heat is transmitted to, the top of these transistors is just like a metal cover. Sure, it gets hot when the transistor heats up, but I personally wouldn't like to rely on it to transfer the heat. Better to try and find an original heatsink, or drill your own from some angle aluminium like I did. I'm actually looking to have these heatsinks re-manufactured by a company that does CNC machining, I will let you know if this ever happens.

Lee.
 
Freetoad, I've got a 3020 that I stepped on. Cracked the circuit board from on end to the other. It was a freakish thing, and I was heart broken. Anyway there's everything there on th board. PM me, we could work out something
 
I would not attempt to make a new heatsink. Find one. Doing otherwise is not really a restore. In that little amp you could throw in a piece of steel and a pair of LM3886s. Might not sound the same but would work.

I don't know how that sink was mounted to the board and chassis, but its removal is not usually required to replace the outputs. As such, I suspect they were removed by a hobbyist for a project.
 
Making a heatsink is as easy as drilling holes in a piece of aluminum. Mouser sells the TO3 mounting kits with mica washers, or you can use the greaseless ones.

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