Hello Anders. Kind help but this is service procedure for standard?3020 type with measure on R653/654. I don´t even have them and PCB board seems shortened under the holes for the resistors. I think there is a separate procedure for series 20 since the board layout is different. The 3020 standard and A, B, E and i version don´t fit in for my amplifier.
thanks
thanks
Hi,
To measure idling current in a NAD 3020 that don't have emitter resistors, you simply remove a link in the path between emitters and insert a resistor there to measure volt. 1Ohm and 25-30mV (25-30mA) is recommended for 3020e and should be fine for your amp to.
Don't forget to short the link again when you are done.
To measure idling current in a NAD 3020 that don't have emitter resistors, you simply remove a link in the path between emitters and insert a resistor there to measure volt. 1Ohm and 25-30mV (25-30mA) is recommended for 3020e and should be fine for your amp to.
Don't forget to short the link again when you are done.
Taiga said:
I stumbled on a place in the UK who'll do an upgrade for you, a few interesting points;
"The main power supply capacitors (originally 4 x 2200uF) are replaced with 2 6800uF capacitors". On mine the 2200uF are 18mm diameter (a bit of an oddball size?) and tightly packed together so I doubt 20mm will fit. Seems like a good idea.
"All electrolytic capacitors in the pre and power amplifier circuits (signal path) are replaced with non-polarised electrolytic capacitors. This has a significant effect on overall distortion levels especially where the capacitors have bi-polar signals applied." Thoughts?
"The output transistors are replaced with modern transistors which have much better sonic properties than the originals, and also provide more power handling capabilities."
Incidentally, I'd like to know just which NAD 3020 model I have. It has 4 x 2200uF caps, but mounted middle-back of the chassis, not front-left as the basic 3020 diagram I have shows, and uses a bridge rectifier, unlike the discrete diode main bridge on the 'A' and 'E schematics I have. Also a bridge on the preamp supply. O/P transistors are 2N3055/MJ2955 and the mains transformer is bolted to the back wall.
No clues on the label, just says '3020'.
cpemma said:
I outboarded some 70,000+70,000 on one unit and was pleased with it.
They are using elcos due to size. Polys for the real critical places & black gates everywhere else would be my suggestion.
I can't recall seeing a 3020 without a bridge rectifier. What is the serial #. Picture?
dave
4fun said:
Hi 4fun
You must remove a link, but in the collector of one of the outputs and insert the 0,1 Ohms resistor for measuring...
If you insert a resistor in the emitters , you change the Vbe of the transistor and when you remove the 0,1 Ohm temporary resistor , the amp will become overbiased....
cpemma said:
I stumbled on a place in the UK who'll do an upgrade for you, a few interesting points;
"The main power supply capacitors (originally 4 x 2200uF) are replaced with 2 6800uF capacitors". On mine the 2200uF are 18mm diameter (a bit of an oddball size?) and tightly packed together so I doubt 20mm will fit. Seems like a good idea.
"All electrolytic capacitors in the pre and power amplifier circuits (signal path) are replaced with non-polarised electrolytic capacitors. This has a significant effect on overall distortion levels especially where the capacitors have bi-polar signals applied." Thoughts?
"The output transistors are replaced with modern transistors which have much better sonic properties than the originals, and also provide more power handling capabilities."
Incidentally, I'd like to know just which NAD 3020 model I have. It has 4 x 2200uF caps, but mounted middle-back of the chassis, not front-left as the basic 3020 diagram I have shows, and uses a bridge rectifier, unlike the discrete diode main bridge on the 'A' and 'E schematics I have. Also a bridge on the preamp supply. O/P transistors are 2N3055/MJ2955 and the mains transformer is bolted to the back wall.
No clues on the label, just says '3020'.
Mine says series 20, which I believe is earlier than the ones which have only 3020 in the name. It is s/n 3270065, made in Taiwan. The layout is like in the service manual with 4x2200 at front left. I replaced them with 5600uF 35V 20mm caps with no problems - they are not snap-in types, so the leads can be bent slightly to fit. I used digi-key p/n 565-1094-ND; you can get a 6800uF unit which is 22mm diameter, and could probably be made to fit if you left leads a bit longer and let them rise off the board slightly. Mine also has a bridge in the main PSU.
Interesting with the history. It would be fun with a chronological serie and updates but that is probably in the shadows of ancient times. I thougt the first modells were UK made. Mine have s/n 3257107 Taiwan made with rectifier bridge only.
Thanks for the tips on Idle Current Alignment but a thought - even if loosing the connection on collector side is a small task it seems very inconvenient for service. I´m sure the Nad team had a smarter way
Thanks for the tips on Idle Current Alignment but a thought - even if loosing the connection on collector side is a small task it seems very inconvenient for service. I´m sure the Nad team had a smarter way
Taiga said:Interesting with the history. It would be fun with a chronological serie and updates but that is probably in the shadows of ancient times. I thougt the first modells were UK made. Mine have s/n 3257107 Taiwan made with rectifier bridge only.
Thanks for the tips on Idle Current Alignment but a thought - even if loosing the connection on collector side is a small task it seems very inconvenient for service. I´m sure the Nad team had a smarter way
NADs were always made in the far east AFAIK ... they were the very 1st to say, let's design in the west and get it built cheap in the east. Now 25+ years later it is almost the norm.
dave
TDWesty said:
Mine's Model No:3020, Serial: A3206003, 'Series 20' on the front panel. NAD publicity I have of the 3020B is missing the 'Series 20' logo shown on the 3020 publicity leaflet.
These leaflets say 3020 Series 20 made to Jan '81, 3020B Jan '84-Jan '87, my 3020e service manual is dated March '89 and there's a 3020i circuit I found. Maybe I have a 3020A... yup, looks like it.
The memory must be failing, I posted in that thread.
Hi vubkevin,
That is not normal.
Tried swapped speakers and the problem with bass moves to the other speaker?
If so, one problem could be in the feedback loop. There is a big (1000uF in 3020b) low voltage electrolytic cap in series with the feedback divider that may have lost capacitance over the years.
The frequency response in the bass depends on this cap. Of course there are other coupling electrolytes as well but mentioned cap is IMO the first one to check.
That is not normal.
Tried swapped speakers and the problem with bass moves to the other speaker?
If so, one problem could be in the feedback loop. There is a big (1000uF in 3020b) low voltage electrolytic cap in series with the feedback divider that may have lost capacitance over the years.
The frequency response in the bass depends on this cap. Of course there are other coupling electrolytes as well but mentioned cap is IMO the first one to check.
vubkevin said:
Hi,
Should I read this that you are sure about that power amp is faulty and which channel is faulty?
If not, have you tried swapped speaker leads and verified that the problem moves to the other speaker?
Since NAD 3020 has line out and main in, you could swap channels here too in order to pinpoint if the fault lies in pre amp or power amp.
There are many parts in the signal path that could be failing so we need to narrow what part (channel/stage) of the amp that is faulty. Maybe you have done this and are sure that a particular power amp channel is faulty, I just wanted to be sure.
Do you have measurement capabilities (scope, signal gen)?
Maybe our conversation should be in a separate thread as it could be seen as thread hijacking.
I don't think it is faux pas to raise an old thread. If so please let me know.
So I have been reviewing the NAD 3020 schematics and I have a question about the preamp power supply. I have not measured it yet but why would you want to have different voltage potential in reference to ground? I see +29.9 and -25.5 on the schematic.
I am still learning this stuff so I am clueless.
Oh the schematic I am reviewing is here.
http://www.tcaas.btinternet.co.uk/nad3020ps.gif
Thanks
So I have been reviewing the NAD 3020 schematics and I have a question about the preamp power supply. I have not measured it yet but why would you want to have different voltage potential in reference to ground? I see +29.9 and -25.5 on the schematic.
I am still learning this stuff so I am clueless.
Oh the schematic I am reviewing is here.
http://www.tcaas.btinternet.co.uk/nad3020ps.gif
Thanks
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