NAD 3020 rebuild

A

AndreasR14

Member
Just got my first NAD 3020.

It sounded okay considering the age, and I'm will recap this.

I've checked the schematics and part lists, however with very limited knowledge and experience I ended up checking the capacitor found in board and plan to replace them with the similar value.

I have no idea which one is signal caps and which one is not.
I know that the signal caps better using bipolar or low leakage caps. however I think I'll go full nichicon KZ when available (seeing the specs it has low leakage anyway) and other nichicon if not in stock.

I found the following caps to be replaced (not sure whether this is original or not):

- Sanyo 68uf 25v -> KZ 100uf 50v (2 caps)
- Matsushita 4.7uf 50v -> FG 4.7uf 50v (1 cap)
- Matsushita 47uf 50v -> VY 1000uf 100v (1cap) - this is the welcome hum cap
- Matsushita 47uf 63v -> KZ 47uf 100v (1cap)
- Triumph 47uf 16v -> KZ 47uf 25v (6 caps)
- Matsushita 47uf 25v -> KZ 47uf 25v (4 caps)
- Matsushita 100uf 10v -> KZ 100uf 50v (2 caps) - I read somewhere this should be 16v minimum
- Matsushita 10uf 25v -> KZ 10uf 100v (2 caps)
- Matsushita 220uf 6.3v -> KZ 220uf 25v (2 caps)
- Matsushita 47uf 25v -> KZ 47uf 25v (4 caps)
- Matsushita 330uf 35v -> KZ 470uf 50v (2 caps)
- Matsushita 47uf 35v -> KZ 47uf 50v (4 caps)
- Matsushita 4.7uf 35v -> FG 4.7uf 50v (2 caps)
- Sanyo 1uf 25v -> FG 1uf 50v (4 caps)
- Matsushita 1000uf 6.3v -> KA 1000uf 16v (2 caps)
- Triumph 47uf 16v -> KZ 47uf 25v (6 caps)
- Matsushita 2200uf 35v -> FW 4700uf 35v (4caps)

Let me know whether this is a proper replacement or will basically make it worse than this.
I'm not worried if I fail as my first project doing full recap.

Several photos:

Inside:
IMG_6341.jpg

With the legendary marantz
IMG_6339.jpg
 
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You should search this site for "NAD 3020" along with member "leesonic".
There will be plenty of hits, @leesonic is very keen on NAD equipment especially the 3020 model.

From your pictures the condition looks original, but I'm not certain.
Edit: the output transistors sure do look like they've been touched.

For sure the 4 centrally located caps look interesting; the 2 of the right-side of the group seem to have the plastic sleeves shrinking....as though the caps are heating up, a sure sign of high ESR.

You are fortunate to have acquired this unit.

Good luck.

--Joe
 
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Thanks for your replies!

yes the transistor looks some of them have been replaced.

I also take a good read on Leesonic’s building thread. He mentioned that wima / low leakage / bipolar caps should be on the signal path.

problems are, idk which one is signal path, and wima and nichicon KLs are hard to get in my country.
 
You might want include the capacitor numbers from the schematic or the circuit board when you posts lists like these, it would make it easier for us to help you out. For example, there are not 68uF capacitors in that amplifier. I can only assume you mean 0.68uF, which would be C529 and C530. Changing these to 100uF caps would have a disastrous effect on the operation of the bass control. For the same reason, changing the "welcome hum" cap to 1000uF would mean there will be a long delay before the muting circuit lifts. My recommendation would be to keep all values as they came from the factory. You can up the voltages on them if need be, and the three in the muting circuit can all be 100v. 4700uF might be a tight squeeze for the main caps, I would go with 3300uF.

You say Nichicon KLs are hard to get in your Country, but it would appear you are able to get lots of the other series, you list mentions KZ, FG, VY, FW. Can you get film caps of any description, they don't have to be WIMAs? Just as long as they fit in the space left by the electrolytic caps, you will be fine. How about Panasonic films?

Lee.
 
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leesonic said:
You might want include the capacitor numbers from the schematic or the circuit board when you posts lists like these, it would make it easier for us to help you out. For example, there are not 68uF capacitors in that amplifier. I can only assume you mean 0.68uF, which would be C529 and C530. Changing these to 100uF caps would have a disastrous effect on the operation of the bass control. For the same reason, changing the "welcome hum" cap to 1000uF would mean there will be a long delay before the muting circuit lifts. My recommendation would be to keep all values as they came from the factory. You can up the voltages on them if need be, and the three in the muting circuit can all be 100v. 4700uF might be a tight squeeze for the main caps, I would go with 3300uF.

You say Nichicon KLs are hard to get in your Country, but it would appear you are able to get lots of the other series, you list mentions KZ, FG, VY, FW. Can you get film caps of any description, they don't have to be WIMAs? Just as long as they fit in the space left by the electrolytic caps, you will be fine. How about Panasonic films?

Lee.
Click to expand...

Thanks for your reply Lee. Yes I was mistaken on the 68uf, should be 0.68uf. I’ll check the panasonic films availability.

Wima mostly available on the high voltage which very big physical size.

The 4700uf fits good as the same size of the old caps that has 2200uf value.

I’m still waiting for the parts to arrive, meanwhile I’ll use KZ first, if it becomes noisy or I don’t like it, might go for alternative films
 
Several of the caps have arrived, so I did replaced what I could

I'll take note on the 0.68uf caps mentioned by @jefferylhenr and @leesonic and ordered Wima 0.68uf MKS10 (this is the one that available) and figure out a way to mount them.
Also the "welcome hum" cap will be changed using the 47uf 100v (instead 1000uf 100v). The original caps was 47uf 50v, however the schematic mentioned about 62.2v which several guys mention that this is the root cause of the welcome hum.

Before recap, there's a slight hum which not affected by volume and this was gone after several recap here and there.

The left channel before recap - DC offset minimum at 0.040v - 0.039v, but after recap it goes up by 0.002 -> becomes 0.042v-0.040v (do i need to change the trimmer to 20k)?

While posting this, I played the after recap one and can't comment yet on the overall sound (I was already impressed on the original condition).

Will update you on the full recap and the sound impression after a week of so.

Here's the old caps that have been removed per this stage
IMG_6381.jpg

The amp running after "half recap"
IMG_6380.jpg

Thank you very much all for several inputs.
 
Here is the mouser # on the .68uf Wima which fits perfectly. 505-MKS0C036800FKC00. This UCC filter cap has great specs for this unit and is same diameter as the original 2200 uf 35 v. # 661-EGXF500ELL332MM4 125 C @
Ripple Current: 3.85 A
 
Thanks Jeff for the trouble.

Unfortunately there's no mouser in my country, but I was able to acquire wima MKS10, which not yet arrived. and I'll find a way to mount it on.

Also, the 5 leds power on my unit is seems unresponsive, I mean volume at 10 o'clock just light up the first led. and 12 o'clock probably 2 leds. but if I put the bass control at max, it will light up the 3rd led.
and 12 o'clock volume is more than enough, I usually listen at 10 o'clock.

Are the led behaviour considered normal? or should I change something to make it more sensitive?
 
Correction, it was actually Wima MKS4 0.68uf 160v, and it still able to fit in.
I also changed the 1000uf 100v caps to 47uf 100v caps which more appropriate.
IMG_6391.jpg

The recap is done now.
IMG_6392.jpg IMG_6394.jpg

For the main filter caps (the 4 big caps) I swap with 4700uf 35v Nichicon FW but the sound seems too bright, I'm not sure this has anything to do with the FW type?
Hence I swap it back to original at the moment.

I still have issues the following:
1. The leds seems unresponsive -> the 5 leds power on my unit is seems unresponsive, I mean volume at 10 o'clock just light up the first led. and 12 o'clock probably 2 leds. but if I put the bass control at max, it will light up the 3rd led.
and 12 o'clock volume is more than enough, I usually listen at 10 o'clock.

2. the DC offset on the left channel can't get to 0, best is 0.039v. I'm planning to change the trimmer to Bourns 20k trimmer, will this helps or basically waste of time?

Thanks guys!
 

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AndreasR14 said:
1. The leds seems unresponsive -> the 5 leds power on my unit is seems unresponsive, I mean volume at 10 o'clock just light up the first led. and 12 o'clock probably 2 leds. but if I put the bass control at max, it will light up the 3rd led.
and 12 o'clock volume is more than enough, I usually listen at 10 o'clock.

2. the DC offset on the left channel can't get to 0, best is 0.039v. I'm planning to change the trimmer to Bourns 20k trimmer, will this helps or basically waste of time?

Thanks guys!
Click to expand...

You could re-calibrate the power meter board if you feel it isn't working as you'd like. There are instructions in the earlier NAD 3020 service manual, most of the ones I've seen just have two resistors. You can replace these with a trimmer if you want to adjust it.

0.039V is a good offset. With 99% of amplifiers, you'll never get to totally zero anyway.
 
AndreasR14 said:
1. The leds seems unresponsive -> the 5 leds power on my unit is seems unresponsive, I mean volume at 10 o'clock just light up the first led. and 12 o'clock probably 2 leds. but if I put the bass control at max, it will light up the 3rd led.
and 12 o'clock volume is more than enough, I usually listen at 10 o'clock.
Click to expand...
Just because you don't listen to it loud enough to light up the LEDs doesn't mean they're unresponsive. NAD equipment tends to get comments something like "The loudest 20 watts I've ever heard". If you can crank it above your comfort level and get them illuminated, that's just a good excuse to buy a less sensitive set of speakers so you can turn it up to light them lights.
 
Thanks Lee and Teal!

That concludes it then.

the recap was done per now and I'll get back in a week time to comments on the sounds.

this was my first recap project with a very minimum knowledge, I can't even read the schematic properly.

I know many ppl out-there would like to recap their NADs and I encourage them to do so, because its quite simple to swap capacitors.

I'll still search for a reasonable price main filter caps. so far I'm out by c.$70 for the caps and stuff. not too bad considering I acquire the amplifier for $125 with no problem whatsoever.

Last but not least, I refinished the top cover with a wrinkle paint
IMG_6403.jpg
 
I had an amp with LED meters starting at 0.01 watts... and even those were barely lit when listening at "night time" levels.

Even cranked to unreasonable volumes, the meter barely exceeded 15 watts (aside the odd peak). People often overestimate how much power is needed to produce a lot of sound in a normal room.

But, you know, I paid for all those LEDs, and dammit, I wanted to use them! So I get it :D In the real world though, the only place you'll want your amp full tilt is on the bench, for a brief test, and not into actual speakers.

Or when someone has set the loud dial to max and you didn't realise, and you drop the needle, closely followed by a "Doc Brown" moment.
 
AndreasR14 said:
Thanks Lee and Teal!

That concludes it then.

the recap was done per now and I'll get back in a week time to comments on the sounds.

this was my first recap project with a very minimum knowledge, I can't even read the schematic properly.

I know many ppl out-there would like to recap their NADs and I encourage them to do so, because its quite simple to swap capacitors.

I'll still search for a reasonable price main filter caps. so far I'm out by c.$70 for the caps and stuff. not too bad considering I acquire the amplifier for $125 with no problem whatsoever.

Last but not least, I refinished the top cover with a wrinkle paint
View attachment 2305929
Click to expand...
These fit perfectly and sound great in my just finished 7020 - 3300 uf 50 v UCC GXF 125 C - 3850 ripple. If these perform to spec new with 2200 uf caps, no need to go above 3300. And @ 18 x 40 mm they are an exact fit and with the outstanding ripple spec.
 
Thanks Jeff!

What a hell of a piece you got there!

UCC is a bit hard to get here, 3850 ripple is quite high isn't it? Nichicon KW or KG specs is at 2200 ish.

Or the higher the better? if yes I can go with panasonic FC!
 
AndreasR14 said:
Thanks Jeff!

What a hell of a piece you got there!

UCC is a bit hard to get here, 3850 ripple is quite high isn't it? Nichicon KW or KG specs is at 2200 ish.

Or the higher the better? if yes I can go with panasonic FC!
Click to expand...
When I read the data sheet, I said damn these are the ones. I got it lit up yesterday for a few minutes. Spent a few hours today buttoning things up and listening via my sacrificial speakers and it’s far beyond expectations. 20 watts putting out this soundstage and sound, no way… Will let the new case paint cure and then hit it with a ceramic automotive treatment. Yes the high ripple current is a good thing, for example the Mundorf 10,000 uf 63 volt mylytic specialized filter caps are only about 6000 @ 100 hz. I used these on the last 3 Luxman’s I restored and the sound awesome. http://www.soniccraft.com/datasheets/Mundorf_MLytic_AG-data.jpg. The UCC GFX https://www.mouser.com/datasheet/2/420/United-Chemi-Con-1016798.pdf
 
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