Another NAD 3020 rebuild and upgrade

[sebalele]

Ciao Lee,
Congratulation ,state of the art NAD!
Next days I'll do the samevrecapping on my nad3020b.
It has been recovered in a bedroom for more than 20 years and some days ago I've switched on my room.
The amp works great but doesn't sound so good.
Appear closed at hi frequency and phono input is a little noise.
I know that this amp is not so dettail or "airy.." But i know that it can sound better .
I've already recapped some receiver from Tandberg and I heard a big improvement in sound.
I have a partial schematics and reading about idle current they said to open R353,356 and misure across them till reading 30mv. I 've found thesecresistor but where I have to fit the trimmer...to adjust this?
There are other 2 trimmer but this help to reach the null output current?

 

[ToniCH]

Leesonic, after your inspiration I bought an another 3020 and today popped them both (3020e & 3020i) open and listed the actual electrolytics on them, I don't trust the service manuals. Brits sure use different value caps to japanese. I do have a quite good stock of caps for my Sansuis but very few are suitable for the Nads if I hope replace them with caps of original values.

Both units seem totally original, haven't seen any evidence of earlier repairs. I did notice that the e and i models are pretty similar but the i has several of the caps upgraded to little higher values compared to the e.

So, I ordered a bunch of caps and some trimmers from Mouser. I hope to start with the 3020e this week. Won't be doing a total dismantle and restoration like you did but a recap to practice my skills and to see if my parts selections make any noticeable difference.

In your experience, what other parts in Nads are most probably worn at this stage and would be smart to renew during this project? Is there anything like bad diodes or fusible resistors, like my Sansuis do, which should always be changed when recapping an old amp?

 

[leesonic]

I have a partial schematics and reading about idle current they said to open R353,356 and misure across them till reading 30mv. I 've found thesecresistor but where I have to fit the trimmer...to adjust this?
There are other 2 trimmer but this help to reach the null output current?

You'll need to fit a trimmer in place of where NAD put resistors. If you look at my picture, you'll see the two blue trimmers closest to the heatsinks are for the bias. The other two, as you correctly state, are to adjust the offset.

Leesonic, after your inspiration I bought an another 3020 and today popped them both (3020e & 3020i) open and listed the actual electrolytics on them.

In your experience, what other parts in Nads are most probably worn at this stage and would be smart to renew during this project? Is there anything like bad diodes or fusible resistors, like my Sansuis do, which should always be changed when recapping an old amp?

The 3020e and 3020i are different inside to the earlier 3020 models. It would be interesting if you start a thread showing your progress on these. Without looking at the circuit diagram (schematic) I can't tell what the differences are.

As for other parts to replace, nothing really springs to mind. Once it's done, you could see if there are any resistors or transistors that run hot (especially in the power supply) and consider upping the wattage (resistor) or adding heatsinks (transistor).

Hope this helps,

Lee.

 

[ToniCH]

The 3020e and 3020i are different inside to the earlier 3020 models. It would be interesting if you start a thread showing your progress on these. ...

As for other parts to replace, nothing really springs to mind. Once it's done, you could see if there are any resistors or transistors that run hot (especially in the power supply) and consider upping the wattage (resistor) or adding heatsinks (transistor).

Hope this helps,

Thanks it really does.

Yes, they are different and I've heard they sound a bit different too. Someone said they went from warm to more "modern" sound during productions changes within various generations (3020, 3020A, 3020B, 3020e, 3020i). But I guess most brands did that coming from 1970's all the way to 1990's.

It seems that 95+% of the resistors used on the 3020e are 1/4W carbon. Metal film preferable replacement?

I will start a thread when I progress with the 3020e and later on move to 3020i. I'll make notes when I spot component upgrades (for example in 3020e they used 6.3V 1000uf and in 3020i 10V 1000uf in the same spot).

Thanks for you help and tips.

 

[sebalele]

Voilà !
recapped has been done successfully , more than 40 capacitor replaced .
I've try to measure capacitance some of them , some like 50% have a low capacitance.
my digital voltmeter can only measure till 1000uF , so I test the smallest.
I've no replaced the big 4700uF *2 ,I've no spare at home.
Bias and output has been adjust like Lee explain .
Resistor for bias has not be changed ; test on shunt current was 22 & 28 mA
First hearing test was not too impressive , sounds a little closed on HF.
I put some signal on loop througth ipod to the aux and phono for more than a day.
Now sound better and seem to hear more dettail.
I suggest to recap if you own an amplifier with more than 30 years of life .Many thanx to Lee for suggestion and inspire.

Ciao !

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[leesonic]

Had to post these pictures in a new reply so I could cut and paste the links back into the earlier threads.

 

[judgedredd]

Here is a view of the front right corner, showing the Alps blue pot I bought from eBay. This was a real pain to fit, the 7020 volume pot bracket wasn't the same as the 3020, of course I only found this out AFTER I'd got the front panel on. I ended up making another one out of a piece of aluminum.

Front left view this time, and you can see the new power switch and the spark suppressor I fitted. I also tied up the transformer primary wires here, since they no longer went to the power outlet sockets on the rear panel.

You see the two browny/red film caps beside the bass control? These were originally blue electrolytics looking very similar to the blue Sanyo ones that fail in other brands.

The two images above do not show up. Please re-post them.

 

[mulos]

Hi, what type of trimmers did you use for replacing RX1/RX2 and VR5/VR6?

 

[tube-a-lou]

Wow, what a great job on this amp, I heard these amps are really good, and a base for good upgrades,
enjoy it.

 

[reubensm]

Hello all, I am doing a NAD3020 resto job currently. Have a quick query, can BD 139 / 140 be used as replacements for the driver transistors, 2N 6551 / 6554? Their specs seems to be almost the same. Also, most of the NAD 3020s that I've come across, seemed to have damaged faceplates. Is there any source from where replacement faceplates can be sourced or fabricated? Thanks in advance.

 

[deanweipa]

Thanks to the main players for all the info, just tested my recapped 3020 with the recommended mods.
Very happy with the outcome, sounds awesome.

 

[Binkman]

G'day mate;
Nice job! Also like your 'sail raft', too!

 

[Sbergman]

Lee thanks for all your info on the 3020!
I am currently about to find courage to start my 3020 (first model) recap, do you still recommend using the caps that are listed in yout "old" spreadsheet? And do you happen to have a link or model number of the trimmers you use for bias? Any other parts you recommend that I get as I would like to get everything home in one order. I am looking to buy from digi-key as Mouser currently have so many of the caps missing in stock.
I am not looking to do a crazy complete rebuild but just to get rid of the hum and see what it sounds like with new caps. It normally runs my kef ref 104 but the humming got too annoying so thought it was time to fix it!

Thanks!

 

[Binkman]

Welcome to AK!...
@leesonic may not respond.. but glad you popped up his post.
bink

 

[leesonic]

I always try to respond, but seem to be busy lately. As Booker T and the MGs might say - "Time is Tight".

I'll try and answer your question in more detail when I get a second.

I have two pairs of KEF 104aBs BTW.

Lee.

 

[Sbergman]

I always try to respond, but seem to be busy lately. As Booker T and the MGs might say - "Time is Tight".

I'll try and answer your question in more detail when I get a second.

I have two pairs of KEF 104aBs BTW.

Lee.

Cool Lee, appriciate it! I will practice my soldering skills while I wait for your input!

 

[Sbergman]

I am underway with my recap @leesonic ! I basically ordered what was in your original docs file, plus some trimmers and a new power switch. I basically got some 20k and some 5k trimmers, any input on what to use? Since the resistor that you swapped it out far was around 1k i figured 20k might make them hard to adjust so I got a smaller one, I am kind of clueless here.
Anyways, I ran into some issues today as I was changing the caps, both on the pre amp power supply, the small horisontal card, and somewhere on the phono amp part there are some 10uF caps. But on the pre amp power supply, these caps are not in the schematic, and are listed as the same number as the 2200uF main PS caps. Any idea what is going on there? And what did you replace them with? I have the earliest version, and my service manual is also earliest version so I am really wondering what is going on. Found a post on another forum with a person making the same discovery but nothing came out of that thread in the end.

 

[leesonic]

20k goes where the original trimmer was, 1k goes in place of RX1/2 to adjust the bias.

There may be some extra 10uF caps here and there, these can be replaced with Nichocon KWs of the same value.

Lee.

 

[Sbergman]

20k goes where the original trimmer was, 1k goes in place of RX1/2 to adjust the bias.

There may be some extra 10uF caps here and there, these can be replaced with Nichocon KWs of the same value.

Lee.

Thanks for a fast reply, I'll get some 10uF caps.
Can I get away with using a 5k for the bias, since that is what I ordered?

 

[leesonic]

Sure, you'll just find more adjustment down one end of the trimmer. If you used Bournes multi-turn, it shouldnt be a problem.