NAD 3020e recapping adventure

[Rohanv]

Hi All,
So I bought a mint NAD 3020e at a garage sale a few weeks ago for a steal, plugged it in much to my surprise, it works perfectly.
Now having had a vintage amp (Rotel 1210) actually explode on me before, I know that old amps need re-capping at this age & not content with a time bomb on my desk, i decided to replace the main power capacitors.

So last night I successfully replaced the 2 main power caps (35v 4700uF) with 50v 4700uF caps and once again the amp works no worries

However,
Now, the speakers emit a slight whump & actuate briefly when i turn the amp on or off. I've had old amps do this on me before, but usually a lot louder..
I would have thought the new power caps would smooth this out, or should i really be re-capping the whole damn thing?
Any ideas?

 

[eclectic2k]

I'd guess the higher ESR of the aging capacitor was limiting the inrush current into the cap. The new cap is likely filling faster, and the larger inrush is causing the turn-on thump.

It's not an especially powerful amp, and not an especially high capacitance, so I'd assume that the "whump" is not very loud either.

If it concerns you, you'll maybe want to look into adding a slow start of some form or another...

 

[Rohanv]

Ahh thanks for that, yeah the 'whump' is soft & isnt too worrying, I was mainly just curious as to the cause of it with new components.

Cheers!

 

[byron99]

Hello,

I had my amp working for over 10 years and it did this every time I turned it on, I believe it was a "feature" of amps of this era 🙂

 

[robotc]

Hi
I have the same problem with switch-on thump. I recall that it seems to be common with this model.
I did a bit of investigation and playing around with the amp a while ago. I found that the thump comes from the preamp. (When I removed the U-link joining the pre and power amps the thump didnt happen.)

There are muting FET's at the output of the preamp with a timing circuit to delay their turn on. I played around with the component values of the circuit and this changed but never completely removed the thump.
For various reasons I never finished my testing. I would be interested to know if anyone has managed to solve this problem.

Bob

 

[Comsat]

I just picked up a 3020e myself and while I like the sound I've noticed that one channel (L) is slightly louder than the other (R). I'm assuming that this could be due to aging capacitors, correct? I'm just wondering how far to go in replacing the caps? Start at power caps and go from there? I'd still have to order the caps from the web so I'd rather have everything or more than I need when I start the job. Anyone have any insight?

 

[asounds]

I would replace all the caps. That will also improve the sound of the amp. If you need the schematic to check all the values and make a general overall let me know. That bump could be also some DC on the exit and the amp needs to be re-adjusted.
The 3020 is probably the most famous amp in Hi-Fi history and for a reason. Great sounding amp 🙂

 

[Comsat]

If you need the schematic to check all the values and make a general overall let me know.

Any assistance helping me get a parts list together would be totally appreciated.

The 3020 is probably the most famous amp in Hi-Fi history and for a reason. Great sounding amp 🙂

I'm eager to find out if the 3020e actually lives up. I've been using an 80's Onkyo TX-28 which is incredibly musical but I've always wanted to wade into the NAD pool and see how the water is.

 

[Comsat]

Again, any help putting together a parts list for my project would be appreciated. I'm perfectly handy with a solder iron and I've recapped some old tube guitar amps but I'm not an engineer.

 

[h_a]

I'm assuming that this could be due to aging capacitors, correct?

I wouldn't think so. As the 3020 was more of a budget amp, I guess the power supply is shared between channels, so it cannot affect only a single channel.

Further, different gain comes more likely from either a cheap channel balance pot or - less likely - from manufacturing variations in the transistors.

You might recap the amp for fun nevertheless if you feel like it.

Hannes

 

[Comsat]

I wouldn't think so. As the 3020 was more of a budget amp, I guess the power supply is shared between channels, so it cannot affect only a single channel.

Agreed, however, the capacitors in one of the channels being out of spec could cause the volume difference, correct?

Further, different gain comes more likely from either a cheap channel balance pot or - less likely - from manufacturing variations in the transistors.

I cleaned the balance pot but I'll give it another good spray to make certain.

You might recap the amp for fun nevertheless if you feel like it.

I plan on recapping the power supply but I'm a little overwhelmed at the prospect of tackling the whole board. Is there a more reasonable collection of caps to replace that will most effect the sound/output? (Assuming, of course, I don't find any that are visibly damaged.)

Thank you.

 

[gazsp]

I've just bought a 3020e and have the same issue, the right channel is output is lower than the left.

Have you had any luck in tracing the problem?

Cheers,
Gaz.

 

[asounds]

I've been away for some time. If anyone needs the Schematics for the 3020 send me PM. My 312 is working like a dream now after the recap

 

[alibenklaus]

I've got a broken 3020e, too, which I'm going to recap completely, so I compiled a list of all the caps:

NAD 3020e caps and shopping list

Cheers,

Ali

 

[riley78]

Hi I have a Nad 3020i with the same problem as described above, higher volume output in right channel channel than left.
If anyone knows the correct caps to replace I'm sure this would help alot of people