NAD3020 New Speaker Terminals and Adjustments
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- Опубліковано 15 лип 2024
- I'm putting the finishing touches on the NAD 3020 Series 20 vintage amplifier I've been working on. // Kindly sponsored by PCBWay - www.pcbway.com/
I added proper screw post/banana plug speaker terminals and am trying my luck with adjusting the idle current and DC offset.
The method I used for the idle current is laid out here (post number 7): audiokarma.org/forums/index.p...
My first video about this amplifier: • NAD 3020 Series 20 Vin...
My second (re-repair) video: • NAD3020 Vintage Amplif...
NAD 3020 Service Manual (for this older model): elektrotanya.com/nad_3020_sm....
TIME STAMPS:
0:00 Introduction
0:51 Replacing the speaker terminals
8:08 Sponsor Message
8:45 Fitting new screw posts
18:24 Replacing a burnt resistor
20:02 Idle current adjustment
42:52 DC offset adjustment
46:27 Cleaning & Reassembly
50:26 Final Testing
50:45 Thank you & Good Night
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Thanks for watching!
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#JanBeta #NAD3020 #VintageAudio #PCBWay - Наука та технологія
Just a small hint when using Solderwick: Just cut it into small pieces instead using the whole roll. As copper is heat-conductive, it will "transport" the heat from your point of the soldering iron all the long way into the roll. So you're loosing temperature. The Solderwick works much better, when limited to a size (2-3 cm) and can be better heated - resulting in much better soaking up the (old) solder...
That makes sense, Im new to this stuff. Thanks for sharing that tip.
I like the work you've done to the NAD 3020 ,what you engineers do to fix these things is brilliant.So us mere mortals can listen to our music again.
I sold my NAD 3020i 2yrs ago, awesome little amp.
Regarding the adjustable resistors, you could have bent the middle pin and solder it to the side pin, shorting them, so that soldering on the board is more stable. I wish I had as much success as you have with my later model NAD 3020i, one channel is blowing the fuse on power up. I'll use the bulb trick in series with the power supply ("dim bulb tester") when I'll have the courage to start an investigation again. :) Congrats for this achievement !
Nice piece of audio history right there! Nice mods!
I enjoyed this video and I learnt a few things from it, Thanks a lot.
12:05 When that hacksaw appeared it reminded me of the first film in the 'Saw' franchise films!
Haha, yeah, I think it’s a similar saw! :D
Thank you for these videos I'm going to try and repair my 3020i
The i models should be pretty similar regarding the circuitry but have some refinements. Hope you manage to fix it! 👍
I have the exact same amplifier.
Is it normal for this amps phono stage to be heavy on the right channel?
Yay more amp work!
I love these new speaker connectors! Definetly the better choice than the other ones. Btw. I've never seen an amplifier with vertical terminals! Quite a good method for connecting things and for saving rear space!
Naa, I would definetly do a little spraypaint job with the upper case! You already put soo much time and effort in this project, this will help the overall result. 😃
Shame it isn't the standard, it's such a pain to have to lean over your stereo and you can't see where you're trying to plug in things.
I know this is a late comment, but just Wow! 🤩 I love the new speaker terminals that you fitted; so much better than the spring-clips!
These old NAD 3020's are absolute classics; the budget conscious audiophile amp of the early 1980s.... a lovely smooth sound, but plenty of power behind it! A good friend of mine back in about '81/82 had one and it was gorgeous to listen to from his Dual CS-502 turntable. I think by then I had a Tandberg receiver with a Rega Planar 3 - that old Tandberg was so warm and sweet sounding, but that NAD was very close behind it for quality audio.... I'd love to find one now for a reasonable price (and in full working order!! 😂 )....... Great job Jan. 👍
Henkel make Loctite branded cyanoacrylate but the Loctite threadlock product are not cyanoacrylate even though many websites selling them falsely claim they are. Of course you can lock threads with cyanoacrylate, its an adhesive. What I like about Loctite anerobic threadlocker product it that their seemingly endless shelf life, you try going back to a bottle of cyanoacryylate in a year and see how liquid it is then. :)
Be careful using anerobic threadlockers near plastic though, they will find knit lines and crack it, keep it away from your precious ABS! Varnish is a better choice in such applications.
nice old hand drawn PCB. Those old NAD amps actually sound pretty good. Beefy TO3 style transistors. This kind of construction was more popular in professional audio.
Ok, it's a class AB amplifier, there should be a small idling current. Looks like your device works like a class B amplifier. Possibly the transistor or diode responsible for the DC offset of the base is broken (shorted) and you transistors don't have an idling current. This will cause distortion, typical for a class B amplifier. The end stage has 4 transistors per channel, 2 push-pull transistors, and 2 pre-amplifiers (darlington configuration). You should see a DC voltage of about 2.8V (4*0.7V) between the the bases of the two pre-amplifier transistors, else your amplifier is not working in class AB. Check between the base of Q612 and Q614 (or Q611 Q613 in some versions) for the 2.8V. On Q610 (or Q609 in some versions) which is the BD139 on the heatsink, the voltage between collector and emitter, should be around 2.1V. The voltage on the diode in series should be 0.7. There's something wrong with your amplifier.
I've seen these with binding posts fitted before... every time I have seen that, whoever did the conversion actually cut away the entire section of PCB under there, and made the connections using wires. It was also typical to find the headphone jack bypassed in that case, and the speaker ground returns soldered directly to the point between the main filter capacitors. Of course, audiophiles will do anything crazy ;)
Also glad you fitted the 0.22 emitter resistors. That solves a lot of problems with thermal runaway in this amplifier, which is often why the output transistors fail - especially if they are replaced with new "epitaxial" construction types
my thoughts exactly, were cut away the pcb track, mount the posts with better spacing, use "solder washers" to wire to the remains of the pcb tracks, thread binder on the posts not soldered up. if Jan has to unfortunately remove the posts again it will be real difficult.
Binder? Help I'd like to understand pls
Go NADs!
hi guys. my understanding of amp bias adjustments is that you would cut the track, remove the .22ohm, substitute the 1k ohm and measure in millivolts to set the required test current. ( isnt this supposed to prevent blowing the fuses). then remove the 1kohm and reinstall the .22 ohm if fitted or just short the break in the track again to use the amp.
According to the later version 3020i, the bias current is set by measuring the voltage across a 1 ohm resistor in the collector circuit of the O/P transistor.
This states a value of 26 to 30 mV, resulting in 35 mA.
I think adjustments on your version could be made using VR5 and VR6.
I appreciate this could result in a slight DC offset at the O/P.
Those aren't traces on that PCB, they're roads!
Highways! 😅
I hope Jan had some Kraftwerk on working on this highway board!
@@tonanornottonull7132 The fun fun fun of the autobahn :-D
@@JanBeta at 40:30... thouse blue precision potentiometers are very low amount of watts.. I think 1/6 watt if i remember correctly......
While the resistors you remove.. they looks like 1/4 or 1/2 watt....
take a look to the other potentiometers in the board.... the resistor trace in thouse potentiometers are at least 3 times the size of the resistor trace inside the precision potentiometer ...
Measure the voltage at the terminals of the resistors when they are on board and running ...
then put the potentiometers back.... and adjust them to have the same voltage in the terminals... see if it works then ...
@@Ramdileo_sys it doesnt matter too much - not much current flows through the VBE multiplier part of the circuit. Those pots will be well within their rating
YEAH !!!!!!
I would have used cables through the holes and wire mounted banana jacks. Too late for tears now though. Might have even been avle to use crimped spade terminals throught the chassi/pcb for extra durability.
Na, das sind doch mal amtliche Anschlussklemmen! 👍 War ehrlich gesagt etwas erschrocken, als du mit diesen billigen Klemmen daherkamst, wo diese 3020er doch einen regelrechten Kultstatus genießen!
I use mine in my home studio so I put 1/4" jacks on mine but it is just straight on the back. it don't have the porch sticking out
To remove the copper traces I think I would have used a Dremel.
....and a portable vacuum cleaning device of some description, to mitigate the small copper particles and lead solder residue created during the removal process.
Like a dentist
I have replaced the speakers wire slots into modern screws and the sound was not the same. I returned old ones and the sound came back to its beauty again. Crazy.
Dood you gotta do a Carver M-400t refurb. Those were awesome amps.
I wonder if Q609/Q610 were blown as well as the driver transistors? They should set the quiescent current in the push-pull output stages, making them Class AB. I wonder how they set it in the first place?
Hi, Jan Beta and kudus for your videos, from Portugal. I really like when you make repairs on amps because I don't understand very much (but) and it's good for learning. By the way, I have one of the new NAD's (NAD C326BEE).
Can you give the link for the binding posts? What do you recommend for vintage speakers?
Hello, we had already talked a long time ago about this Nad and mine that had a problem that the woofer moved to explode without sound.
This was after doing the full Recap
They calibrated it for me and it sounds good but now I have a lack of bass, I realize that other amplifiers move the same Woofers and at Nad it's like it doesn't.
Does yours have tremendous bass or is it very modest when you crank it up to the max?
Can you show a pic of the Iddle current allignment please, thanks Jan
Waow looks. Like
Hi is there any reason why you do not have soldered 4 wires to connect the board traces to the binding posts you could have put in the space on the rigth side of the original binding post base. There would be no need to scratch the traces and you could have separate each post more than you had done. However I congratulate with you for this very interesting and informative work.
I have always liked the older NAD gear but it seems that the boards where never soldered very well. I have a 3020i and had to pull the board and re-solder the whole thing due to cold joints that plagued these units. The boards are always covered in flux residue and dirty. The speaker relays are always going bad too but that can be expected with mechanical relays that are 40 to 50 years old so that's not that big of a deal.
For all that work on the terminals - could have staggered the posts front-back-front-back to get the spacing and not have to carve away the circuit traces.
There was no need to insert the 0.22 ohm resistors. You could just have broken one of the 2 paths, measure the current with a mA meter, do the adjustment, and fix the path.
I've got a nad 310
I have never owned a NAD amp, but I used to deal with them often as an A/V installer. I can't say I ever ran into an issue with one but I do remember them being pricey.
Oh they have their issues, as they are built fairly cheaply. But they are still nice and have a mellow sound signature, and pretty powerfull for their ratings.
I might be wrong, but I had a Nad 701, and to adjust the Idle current you removed the solder short and put a meter on the opposing sides with no Resistor crossing it. I think what is happening, you are shorting the measuring circuit with the resistors you have added, thus no reading on your meter.
Guess I better add a hacksaw to my electronics arsenal... :D
Every good tinkerer needs a good hacksaw! 😅
at 40:30... thouse blue precision potentiometers are very low amount of whats Jan (@Jan Beta).. I think 1/6 whats if i remember correctly......
while the resistors you remove .. looks like 1/4 or 1/2 whatt....
take a look to the other potentiometers in the board.... the resistor trace in thouse are at least 3 times the size of the resistor trace inside the precision potentiometer ...
Measure the voltage at the terminals of the resistors when they are on board and running ...
then put the potentiometers back.... and adjust them to have the same voltage in the terminals... see if it works then ...
Hello Jan, I enjoyed this video and I currently have an NAD 3020 on my bench for a capacitor refresh. May I ask what you are using to secure the power transistor screws (the blue stuff)? I would like to order some of it. Thanks.
Don’t laugh, but I used some left over nail polish for that. If you want to use something more professional, I’d recommend loctite. ;)
@@JanBeta I have some old car touch up paint in my shop that is thickened. I'll give that a try.
What is the hole and broken paths in the PCB at 27:27?
Those are better speaker connectors but I'd be worried that since they go into a circuit board instead of a chassis that the board may get broken.
It doesn't make sense that one channel would use a 1.5Kohm resistor and the other would use 1.2 Kohm. They are supposed to be identical, unless someone has done the idling current measurement during production and inserted the appropriate resistors.
Probably because the power transistors wasn't a matching pair due to a difference in hFE (or βeta). All high end amps have selected transistors installed which are extremely close to a perfect match. To overcome that you can fit different values of passive components. The same goes with thermionic valves which can be selected by testing them.
Saw one of the posts, test if it fits and holds on good enough then saw the others.
Why would that resistor to ground be so burnt?
"That detective, is the right question."
I have no idea how the previous owner managed to do that. They probably connected something VERY wrong. 😅
@@JanBeta probably mains voltage?
Hi Jan... May I ask what model hot air station you got, and are you happy with it?
I have a variant of the 858D (the Same model is available under a variety of brand names). Very inexpensive and good enough for infrequent use. There are definitely way better ones but this one is the least expensive. ;)
Did you know that NAD stands for New Acoustic Dimension ? I read it somewhere....
Where there revisions all the way from 3020 to 3020i ? I think I have seen 3020a but perhaps that is this model.
Yes, it says so on the back panel even. I think the early versions (like the one I have) are referred to as the "a" model. Maybe it even says so somewhere for slightly newer revisions. The "e" and "I" models are later incarnations with slightly refined circuits.
I have the A version
Why NAD removed the emitter followers is beyond me. Good plan fitting some.
Budget cut. The original hometaxial made 2955/3055 pairs worked fine without them. Modern epitaxial types go into thermal runaway.
@4:30 Burned out resistor to the far right of the board? Apologies if Ive missed something explaining this, running the video in the background whilst doing other things today.
Yes, I fixed that in the video. It’s the resistor that goes to the ground terminal for connecting turntables. No idea how the previous owner managed to burn it!
@@JanBeta I was also wondering "how?". What could you put across it that would make it cook? Faulty deck maybe?
@@Neffers_UK likely mains voltage as the resistor value is too large the burn up unless a high voltage.
@@Neffers_UK There was originally another input bodged onto the connections. I suspect that is what caused it.
The negative speaker terminals are not common, you should have used the second one when adjusting DC bias voltage.
they are indeed common
When he fitted the binding posts he tested negative to negative and they were a dead short, so they are common.
I tend to think that you may have a device out of specification, I cannot be certain of course. I would be checking components in the gain stage. Do you have transistors that are *exactly* the same as shown in the schematic? It almost looks like someone may have messed with this area, perhaps different transistors were used thereby requiring a lower gain signal from where you were measuring and the only "fix" was to lower the original gain signal; this would make your procedure more than a little bit off. One thing you can do is use a little math. What is the expected signal voltage if your loss over a 0.22ohm resistor is 5-10 millivolts = Xvolts? Then test that same point with black wire to actual ground, to see if you are actually getting Xvolts in the first place. If not, something is either modified or there is a problem in your signal path. Follow the traces or look at the schematic to determine that signal path and test the components along the way.
The driver stage transistors are higher voltage rated ones but they should still have the same current draw. The power transistors are original. I couldn’t find any other mods really but maybe I’m missing something obvious. No idea still!
Setting thise voltages with analog meter is beter. It gives a bettervaverage reading than digital meter.
Put pin in accu drill, put saw on right spot, spin drill …
18:54 that burnt resistor cannot be 47 kilo-ohms. to be burnt like that, it had to sustain at least 10 watts, and that means 700 volts across that resistor!
it was a 1 watt resistor
Step drill bit would of best.
Getting superglue on your skin isn't so bad... but absolutely avoid getting it on clothing, it instantly cures on contact with cotton (with a lot of exothermal heat too) and you will tear your clothing before getting it apart.
Oh, yes, I’ve "tried" that, too. Definitely not recommended! 😅
And don't get it in your eyes. I have a colleague who was applying CA glue and the tip had a slight blockage. He squeezed the tube really hard, it squirted out, splashed back and got him in the eye.
MY EYES ARE BLEEDING
Jan Beta - der „Heimwerkerkönig“
I would prefer the original "Hirschman"-terminals, they are much better quality than the china-version.
Yes, those are probably better quality! The ones I used feel pretty good, too, otherwise I wouldn’t have used them.
Hai fatto bene a cambiare il modello dei connettori,sono migliori e i cavi sono serrati bene
Here link for adjustment: ua-cam.com/video/FkxiryiXEUw/v-deo.html
That’s the newer version of the 3020 with a slightly different power amp stage (which makes it more straightforward to adjust).
YT are really scraping the barrel with the adverts they are now endorsing, regrowing teeth! Whatever next, new arm, leg?
What?! 😅 Didn’t see that particular one yet but they surely have some weird stuff going on. Unfortunately I don’t have any control about which ads are shown.
Never been a fan of that back panel design
what a hack :(
I am not a fan of this kind of "home made improvments" on ams from 70s - its almost 50yrs old amp!
Completely understand that! I usually try to stay close to the original specs with these restorations. Unfortunately, the original speaker terminals were crumbling and broken and there’s is no 100% accurate replacements available. So I went with this option to at least make it useable again.
Ist das dein Ernst ?? Du redest englisch mit deutschem Akzent um was zu erreichen ?? Dann die Techniken die du hier zeigst sind nur wildes gebastel. Dein geballtes Halbwissen ist nicht wirklich lustig. Es wäre also besser, wenn du nicht so viel laberst, sondern dich mehr auf die Ausführung der Arbeiten konzentrierst.... Nun ist dein Gerät nicht meher original und verliert dadurch an Wert. Denkst du das es nun besser klingt ?
Yo, mein voller Ernst, Baby. Und ich mache mit meinen Geräten, was ich will. Musst du ja nicht nachbasteln geschweige denn anschauen. Gibt jede Menge nette Leute, die keine Kartoffeln sind und mein Englisch ganz gut verstehen. Peace out und danke für die „konstruktive“ Kritik. 🤪