NAD 3020 with loud hum. A couple of simple questions. - diyAudio
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Old 12th January 2009, 06:22 PM   #1
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Default NAD 3020 with loud hum. A couple of simple questions.

Hi! I'm so glad I've just found this forum. So many interesting posts and a lots of love for my ol' faithful amplifier, the NAD 3020.

Yesterday, after nearly 30 years in the family, my NAD 3020 developed a humming noise. I'm not too much of an expert but I'd say it is a constant low frequency noise (sub bassy) and is about 50% of the volume of what's being played. I've disconnected everything apart from the power lead and two speakers and it still hums.

Here are some details:

1. I have added no new electrical devices or changed any electrics in my house recently. The set up has been the same for months.

2. When the input selector is anything apart from the phono button (i.e. Tape, Aux, Tuner) the hum is much less but still affected by the balance, bass and treble, but not affected by the volume knob.

3. When phono is selected the hum is much louder and is affected by the volume dial. You can hear it (quite loudly) when volume is at zero and turning the volume past 12 o'clock is unbearable.

4. When I remove the pre-amp jumpers at the back of the unit the hum is still audible but always sounds exactly as it did in point 2 above, even with the Phono input.

5. My 3020 has had static issues for a few years but I've found a good clean and some contact spray usually sorts this out. The main area I've had difficulty with is the area behind the power switch. Those two big disc-shaped capacitors are always giving me crackling problems and I can even see little red lights occassionaly flashing in the switch they're connected to.

Now after that huge info dump I just really have a few questions to ask you in the hope that I can maybe save a bit of time and money by drawing on the collective knowledge of the board members here.

Q1. Does this sound like a simple case of replacing the capacitors at the power switch? I think they power the pre-amp too.

Q2. Does this sound more like a bigger issue with the pre-amp circuit board?

Q3. Or does this really sound like a huge headache, and I should go buy a new amp?

Look forward to seeing what you suggest. Thanks in advance!

John..
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Old 12th January 2009, 08:10 PM   #2
mjf is offline mjf  Austria
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hello.
perhaps there is something wrong with your power supply.first i would look at the rectifiers(damaged diode or so....),
and then at the electrolytic caps in the supply
greetings...........
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Old 12th January 2009, 10:02 PM   #3
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i have had many of these amps over the years, the problem you describe is the 4 big power supply caps, you need to replace these, also to solve the power switch crackling problem replace the switch (this is what is causing the crackling) while you do this replace the caps that are connected to the switch.

chris
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Old 13th January 2009, 02:15 AM   #4
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Thanks guys. I'll probably get a local Brighton repair guy to fix all those capacitors and switch for me as it may be beyond my own skills.

If I show him which capacitors need changing would it be a simple job for him to find the right ones as well as a suitable new switch, i.e. will he need a NAD switch or a generic one?

I have seen a few 3020 schematics online, and even some detailed upgrade write-ups so I'll probably print them out and take them along with me if they need them.

Anyway, thanks for the help. Can't wait for another 30 years of unique audio from my NAD

John..
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Old 13th January 2009, 03:36 AM   #5
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Old 6th November 2010, 04:12 PM   #6
gbh001 is offline gbh001  United Kingdom
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Default NAD 3020 hum problem

I have the same issue with my NAD 3020 which I started using after many years of storage because I re-discovered how good it was with vinyl. After a few weeks of use it started humming/buzzing as described in this thread. The hum is not affected by the volume control.

I replaced the 4 big 2200mf power supply capacitors as I suspected them and because they had oozed orange goo! But I still have the problem.

I tried isolating the pre amp by removing the jumpers and connecting my CD player to the power amp. It still hummed so I guess not the caps there.

I'd really appreciate any advice as to what to look at next. I'm no expert but I realize it must be something in the power supply side.

Many thanks
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Old 6th November 2010, 04:15 PM   #7
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The culprit could well be caps in the regulator.

dave
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Old 6th November 2010, 04:53 PM   #8
gbh001 is offline gbh001  United Kingdom
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OK, thanks - that's on the board attached to the back, a couple of fairly large caps I think? Will try this..
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Old 7th November 2010, 01:32 AM   #9
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I have a 3020. I believe any 3020 is worth fixing. You may find some worthwhile info @ tnt-audio.com

VERY low (60hz) hum? My $'s on rectifier(s). Mines on loan to a non techie or I'd ask him to check the PS voltage for ya.

You could check the PS voltage between the caps & ground. Then, if it looks easy, disconnect the caps & check it again. If the caps are good the 2nd reading should be about 30% lower. If you see a smaller difference....

You'll hear leaky caps as distortion; all failed as 120hz hum plus distortion. .

Cheers tony
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Old 22nd January 2012, 08:25 AM   #10
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hai planet 10 my name is benjamin i have a nad 3020i
and it crackles when i turn it on and there is a loud hum when the power button is pushed after 10 second the hums goes a way NEED HELP FROM A PRO


Please help
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