nad 302 problem (please help!)

[teknichian]

hi! i've got a trusty good nad 302 from '95.
for some time past this amp do weird things. sometimes (not all the time) one of the 2 channel (left or right) starts to distort or fuzz on low frequencies (cca.:40-60Hz). i'm not sure that it's a real distortion, maybe something else, but its only on sub/low freq, never on mid and highs.
especially when the source is a sinus from a sound editor (for example:soundforge). it's very strange.

at first i thought it's a withering cap. so i changed the original electrolyte capacitors (6800uF) to 10000uF, but it didn't solved the problem. (the lows got warmer & fatter)
this strange thing is not exits on headphone output on my senn hd570, only on my polk loudspeakers, but i checked them so not the speakers went wrong.

i checked all the pots on the amp: bass, treble, balance, tone defeat etc... but nothing is wrong.

could it be the volume potmeter? 'cause it's old? shall i use a proper spray on it - will it use?

or can it be a transistor or a resistance? perhaps a a coupler capacitor?

it would be a big help if you could give me the schematics of the NAD 302, because i try to search it on the net but i could not find it.

thx for the help...

[Andy L. Francis]

You wrote: 40...60Hz. Maybe then it's some mains hum (50Hz in your country)?
First I'd searching for wrong contacts/solderings (input connector, vol-potmeter, signal cables, etc...)!

[teknichian]

i checked the solderings & contacts as well, oddly at the warming parts, for example: power supply, power transistors.
and what is more i soldered it again...

[reddish75]

i have the manual send me your e-mail and ill send it over,
i also have this amp with a problem that the left channel is a slightly quiter than the right, and have'nt managed to track the problem down yet! anyone with any ideas on where to look?

thanks
chris

[teknichian]

hi!

it would be a big help if you could send me the service manual of the NAD 302. my email address is: bbittera@gmail.com
thx a lot.

greetings from hungary.

[Leonfijen]

Originally posted by reddish75
i have the manual send me your e-mail and ill send it over,
i also have this amp with a problem that the left channel is a slightly quiter than the right, and have'nt managed to track the problem down yet! anyone with any ideas on where to look?

thanks
chris

Hoi Chris,
I have some problems with the powerpart of the NAD302. It looks like the voltages are to low. Do you have probably the schematics and do you have mayby some tips to solve mine power problems.
Thx, best regards, Leon (fyenleon@pi.net)

[marekst]

Hi teknichian,
I can’t help you with NAD but you have my sympathy.
I need your help on another subject: How do you pronounce the last name of a Hungarian composer Zoltan Kodaly? I need the original, not the English pronunciation. The Americans pronounce it: “Koday”. As if the letter “l” wasn’t there and the “y” at the end as in “buy”.
Thanks,
Marek Stojek