Hello.
NAD 3020B.
Right channel works fine,tone control ok.
Left channel works fine but impossible to adjust treble or bass.
Loud knob not works also on left channel.
Balance works fine on 2 Channels.
Regards.
SM
https://elektrotanya.com/nad_3020b-int-sch_2.pdf/download.html
NAD 3020B.
Right channel works fine,tone control ok.
Left channel works fine but impossible to adjust treble or bass.
Loud knob not works also on left channel.
Balance works fine on 2 Channels.
Regards.
SM
https://elektrotanya.com/nad_3020b-int-sch_2.pdf/download.html
Probably a bad capacitor knowing its age. My guess is the signal path through C525/526 or a component break in this feedback loop.
You state 'balance works fine on 2 channels'. There is no balance control ... ?
You state 'balance works fine on 2 channels'. There is no balance control ... ?
subject repeatedly discussed on the 3020, a complete recap is almost always essential on this amp.
It's long and tedious but the result is worth the work.
there is somewhere on the forum the list of capacitors for the 3020 series 20, A and B, you have to search a little but it exists.
it is also necessary on certain series to take again the welds and to replace the resistance of power on the supply circuit of the VU meter
It's long and tedious but the result is worth the work.
there is somewhere on the forum the list of capacitors for the 3020 series 20, A and B, you have to search a little but it exists.
it is also necessary on certain series to take again the welds and to replace the resistance of power on the supply circuit of the VU meter
Hi . If there is no loss of connectivity from emitters q501 0502 to corresponding capacitor ,and capacitors are new and ok ,then check potentiometers with dmm . Or ...leave them in middle position , and try to short carefully middle pin (slider) with one ,then with second ends of bad channel ,for high frequency pot first ,then bass potentiometer. If tone would change , pots needs replacement or at least service ,if that possible at all.
All voltages are ok on bad channel.
No bad caps.
I desoldered all caps on left canal and replaced suspects.
I also noticed that the left channel is less powerful than the right .
Power amplifier works fine on both channels
No bad caps.
I desoldered all caps on left canal and replaced suspects.
I also noticed that the left channel is less powerful than the right .
Power amplifier works fine on both channels
Q501 Q503 Q505 Q507 are ok.
I swapped them with a working channel.
Q509 is shorted but I don't think it's because of him
I swapped them with a working channel.
Q509 is shorted but I don't think it's because of him
If transistors would have failed ,you had no sound in that channel . Did you tried measure tone control potentiometrs ?
Q509 and Q510 are just like switches ,but they have some resistance to signal ,depending on load ,you may try temporarily short both .Also if balance pot will have different resistances from viper to ends ,or one end not connected ,by broken track or pot ,you will have exact effect you mentioned,of one channel less powerful . Also i see c513 c514 , those are also feedback related ,have you changed them ? Sometimes capacitor measure capacitance ok ,but can have series resistance of 300 ohm or even more ,and then you need just replace it to be sure .
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i have swapped Q509 and Q510.....no results.
2 potentiometers are ok.
I remind you that the button loudness also does not work on the left channel
2 potentiometers are ok.
I remind you that the button loudness also does not work on the left channel
About loudness control .Its related to volume potentiometer ,which has special tap ,designed for that ,and switch sw6 .Again ,you need to measure potentiometer and switch resistances ,switches mostly require cleaning of contacts .Loudness control is before tone control by signal path . For potentiometers need to measure how slider to ends resistance changes while adjusting potentiometer .
Cleaning is not enough ,if track inside potentiomer is weared ,or slider damaged and have no contact . Need to ensure that resistance changes properly on both potentiometer channels ,in your schematic they are stereo.
C519, C520 ? Potentiometers are never identicals .So if tone control not works completely for both low and high frequencies for one channel ,it must be broken track or something like that . Which components corresponds to L channel in schematic ? Upper or closer to middle ? C519 or C520 ?