NAD 3130 Amplifier-same fault 15 years apart!!

[Old Sparky]

Thanks for reading my posts on diyaudio.com. and clarifying the difference between Iq and DC offset, mark, though I did know that, in the case of the A3i and other amps. with emitter resistors, the Iq can be easily calculated by ohms law once the voltage drop across the emitter resistors has been measured, and in one of my posts about the A3i, I did note that I had confused the DC offset (which, of course is measured across the speaker terminals, or, as in most cases the speaker neg. is grounded, between the positive speaker terminal and earth)., and should ideally be zero. Should know better than to mix the two parameters up after almost 50 years!!

[Old Sparky]

The two Nad amps. in my 'to do ASAP' pile are a model 302 and 3020. As these appear to have similar circuits and heatsinking arrangements to the 3130, I may consider fitting a thermal trip to these two 'when I get a roundtuit!' This old thread has given me some useful info. on which to ponder.

[Old Sparky]

Having put the 3020 on my bench yesterday - it has/had an intermittent fault which i traced to around the pre-amp./power amp. area, it seems to me that the cause was simply bad connections in the phono sockets where the (original) metal jumper loops are fitted. Having cleaed both the jumpers and the sockets, the 3020 is working, so I'll put that one on soak test when next in the W/S. Maybe fitting new good quality phono sockets at these points will make for long-term reliable operation, then possibly fitting a thermal trip to the heatsink.

[Old Sparky]

I ran the 3020 for over 3 hours this afternoon, playing CDs as I've doing with a Cambridge amp., with no sign of any failure, so, especially with other thing to do, I'm wondering whether to replace the RCA sockets as a precaution. After all the 3020 is probably around 30 years old by now

[boater sam]

You would be better replacing them, otherwise in 15 years time it may come back to you again.
Do the job properly this time!

[Old Sparky]

I guess your comment was a bit 'tongue in cheek', Sam. The 3020 is a different amplifier to the original subject of this thread, though they all use the same type of RCA)Phono_ sockets and the metal links between pre and power amp stages. Anyway as I'm now 76 I doubt I'll still be repairing amplifiers, etc., in 15 years' time!!

[ppppenguin]

I never even thought of replacing phono sockets except where they were mechanically damaged.

[boater sam]

I guess your comment was a bit 'tongue in cheek', Sam.  The 3020 is a different amplifier to the original subject of this thread, though they all use the same type of RCA)Phono_ sockets and the metal links between pre and power amp stages.  Anyway as I'm now 76 I doubt I'll still be repairing amplifiers, etc., in 15 years' time!!

It was a very cheeky comment but let's hope that we could all carry on fixing stuff for another 15 years. Then again, who else will be fixing amps and radios?

[Old Sparky]

To return to the 3130 which was the original subject of this thread, in 4 years I've no seen it again, so presumably it has continued to function properly. This being the case, I may fit 70 degree thermal trips on any NAD amplifier of this series-I have two in the W/S at the moment- and possibly on other amplifiers of similar design & construction. Might even think of adding, where practicable, o/p transistor emitter resistors of between 0.22 & 0.47 ohms each.