Need help w/ NAD preamp problem

[Jim B]

Hi everyone,

I recently hauled my NAD amp and preamp out of the basement after 5 years of non-use, and hooked them up to my cd player, and later my tape deck.

Basically, I get a very weak sound. If I put my headphones in the amp jack, I get a weak sound. This is also the case when speakers are hooked up.

When I put the headphones into the jack on the preamp, the sound is even fainter; barely able to hear it on full volume.

When listening through the amp, the tone and balance controls on the preamp to affect the sound, so they are working.

I've eliminated the interconnects as a source of the problem.

I took the preamp into my local stereo shop where I had purchased it 20 years ago, and they had the same problem with it, very weak sound.

They did refer me to a repair shop, but I thought I would give it a shot myself first. Not to be cheap, but I my son is starting to get into stereo gear, and I thought we could work on it together.

Thanks for any advice you could give.

Jim B.

 

[djk]

Make sure the tape monitor is off.

Make sure the pre amp-power amp coupler switch is on or the jumpers installed.

Try removing the j-fet mute transistors.

 

[Jim B]

Thanks for your help.

But with a separate amp and pre-amp would there be jumpers or a coupling? Wouldn't that just be in an integrated amp?



Jim B

 

[djk]

My tips were intended to be generic, for NAD receiver and integrated owners too.

Some Hafler preamps have problems with muting fets too.

I've also had problems with Yamaha tuners.

 

[Jim B]

Thanks again

 

[hjelm]

What model is the preamp?

As for just guessing a bad PSU might cause this.
Basing this on the fact that the sound semms ok(?) but at a low volume.

Look at the voltage you have when driving the headphones.

 

[Jim B]

It's a model 1020, made around 1982.

As far as I can tell, the sound seems OK, just weak.

Thanks for your help

 

[hjelm]

Does anyone have a schematic?
I think it is fun but without schematic i cannot help.

 

[Jim B]

Thanks Hjelm,

I don't have a manual, but will see if I can find a schematic on the web somewhere.

 

[soma]

Step by step

Pls follow below steps to repair,if there are any founds,pls let me know,I will try to give a quickest comments.
1)Pls check voltage of Q901(2SD669) e,to check whether is +23.3V and check if Q902(2SB649) e is -20.2V or not?
2)Try to use tweezer to short d and s of Q509(2SJ111) and Q510(2SJ111),and check whether output is normal in the corresponding channels.

 

[Jim B]

Soma,

Thanks so much for your detailed reply. Unfortunately, your instructions were beyond my limited technical knowledge. But I may be able to get my brother-in-law to give me help.

Thanks again

 

[peepoo]

Hi,

I have exact same problem and same model here. Somebody told me it causes from Power supply capacitors. Can you get through it? and how'd u fix it? Please let me know. thank you.

 

[da_madaxeman]

I ALSO have a NAD amp which does the same thing... LOL

My amp (whole unit) is a NAD 3140 made in Taiwan. I found it on the side of the street on hard rubbish night, so if I don't get it to work it is no great loss. Some of the board is a little rusty but appears only to be the VUs.. And I am in the process of testing it all with a circuit tester and it seems ok so far.

I also get a very weak output on full blast. This isn't my thread, and I don't know if my amp is the same model... And I'm not hugely knowledgeable with electronics so if it's too much hassle don't worry about mine, but any help is appreciated. How does one test capacitors, etc? I know how to test resistors, and if a circuit is broken of course.. But besides that...

If you ask me to test any part of my amp you'll have to spell it out but I'll be happy to contribute and even happier to have a go at fixing it 😛

-Eli

 

[da_madaxeman]

Uhh, I'm a complete idiot. Sorry!

There was a Pre Out and Normal In on the back of the amp. I just had to join the two

Solve your problem? lol! Sorry for disturbing you all...

-Eli