It’s so nice to come into the play pen and have presented, an amplifier which is not some stupid Class D rubbish with a 1000 components blown up, which in any case you cannot see without the use of a Hubble Telescope. Here we have a nice NAD 3130 amplifier. Owner was upset that it started humming, then went dead.
Off with the bonnet and a quick test around with a real meter, AVO 8. Both 4 Amp fuses blown and one channel’s output transistors all short circuit. Nice standard set up, complimentary 2N3055, 2955 set up. This taking me back to the ‘70s, when children could run free in the green fields and you didn’t have to worry about having a sense of humour and having your mental health battered by a simple joke.
Out with the faulty parts and a test for other damaged bits. A power up with a signal into the tuner input. At the speaker terminals, an output was present on both channels, no load. This meant the drivers in the faulty channel were okay and lived to fight another day.
In with a couple of new 2N….s and new mica insulators. Yes. Always. These can be punctured and in this case, was probably the cause of the failure. Set up the bias which was spot on anyway and a clean of the user controls. Some strange gurgling noises on the left channel was traced to a duff electrolytic capdensor.
Wonderful sound, lovely, fundimould in full musicality. So good, I did a dance-imost in the offie and bumped my chilblaker.