Naim Nait 2 - Phone Stage is out of Balance

[phosgen]

Hi there

I own this baby since many, many years. I think my Nait2 is about 20 years old. I never had any problems with it but now the phono stage is out of balance. All other input stages as well as the power amp section are working perfectly balanced (meaning left and right channel a balanced). It seems to me that one phono channel is working at normal output level whereas the other one has significantly lower output level and sounds thinner than the other phono channel. It's definitely not my turntable that is providing an unbalanced signal between left and right channel (I've switched the channels in order to exclude the turntable as root cause.
Since the rest of the Nait amplfier sections are working properly the issue must be located within the phono pre-amp section.

I know from tube amps that electrolytic caps dry out and need to be replaced after 15 to 20 years. Could it be the case that the electrolytic capacitors in the phono section have been dried out (these axial 47uF/25V)?

I've got a picture on phono pre amp section here:
Cloning the Nait 2 - Page 3 - pink fish media

Any advice out there?

cheers
/ martin

 

[Mooly]

Yes, that's a possibility but it wouldn't be expected at this age and these caps would normally have an easy life anyway. These kind of faults respond well to 'test and measurement' but in the absence of an oscilloscope and suitable signal source you just have to go with trial and error.

It would be worth a quick comparison of the DC voltages too (all the transistors), comparing one channel with the other. There should be no more than say 10% difference in the DC conditions. Make sure the volume is turned down while poking and prodding the circuit.

Changing all the electrolytics is a few minutes work and costs very little parts wise.

 

[phosgen]

Hi Mooly

thanks for the instructions. I'll do that as soon I have enough time.

Replacing the amp's electrolytic caps is on my radar anyway. I've once replaced the caps in one of my guitar tube amps power supply. It made a huge difference in tone and dynamics.

cheers
/ martin

 

[Mooly]

You're welcome Just take it slowly and methodically and you've a good chance of sorting this one.

 

[analog_sa]

Before changing any parts i would clean properly the phono jacks with Deoxit or even replace them if possible.