FOUND ITTTTTTTT
Get this...
The outer ring of the RCAs on the input board go to pin 10 of J602 which leads to the volume control board. On the volume control board, pin 10 of this connector is connected to pins 8, 6 & 4. Back to the Input board, pin 4 is connected to a jumper which is connected to the 0v ground. There was a tiny tear in the trace between pin 4 and this jumper - who knows how the live speaker cables caused that to happen!?
I've fixed this, and now ground is showing everywhere. Just going to reassemble a bit and report on what the amp is doing now. Thanks so much you guys. I have a feeling the engineers at NAD were in a dark basement cackling away at the poor soles who might try to repair this one day.
Get this...
The outer ring of the RCAs on the input board go to pin 10 of J602 which leads to the volume control board. On the volume control board, pin 10 of this connector is connected to pins 8, 6 & 4. Back to the Input board, pin 4 is connected to a jumper which is connected to the 0v ground. There was a tiny tear in the trace between pin 4 and this jumper - who knows how the live speaker cables caused that to happen!?
I've fixed this, and now ground is showing everywhere. Just going to reassemble a bit and report on what the amp is doing now. Thanks so much you guys. I have a feeling the engineers at NAD were in a dark basement cackling away at the poor soles who might try to repair this one day.
That's it guys - it's fixed and sounds great. My god, I love you all. Special thanks to Mooly who called it twice in a row.
Still scratching my head about how that trace tore - I've never seen a trace damaged from something like this, aside from when it was caused by a component which burned near it.
It was an incredibly subtle tear I must say. Since that tear was causing the fade out fault, and the fade out fault was caused by the speaker wire, which happened before it was EVER opened, it seems like it must have been caused by that - somehow.
Still scratching my head about how that trace tore - I've never seen a trace damaged from something like this, aside from when it was caused by a component which burned near it.
It was an incredibly subtle tear I must say. Since that tear was causing the fade out fault, and the fade out fault was caused by the speaker wire, which happened before it was EVER opened, it seems like it must have been caused by that - somehow.
@ Passmore good for you that's great news when you mention tear are you referring to a crack in the trace? and if so how did you repair it? just curious
When ever i run across a bad trace i will reinforce it with some very small teflon coated wire i got years ago from radio shack.
Yes Mooly helped me also he's a Gem.
When ever i run across a bad trace i will reinforce it with some very small teflon coated wire i got years ago from radio shack.
Yes Mooly helped me also he's a Gem.
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The trace was very short, about 5mm - i just cut a bit off a leg of a capacitor and ran it between the two points the trace was supposed to connect.
I've been informed it was definitely the other end of one of the speaker cables, maybe he had it REALLY loud? Thanks for your aid in the matter!
Thanks so much for sticking with me - i really wasn't sure we were going to get there at one point.
I repeat my earlier sentiments - this is an amazing place! Respect and gratitude to you all.
I think, because the inputs and quite a few grounds were still connected together?
Hello my friends!
I'm afraid this amp has a new, exciting problem.
Here's what happens...
You turn it on, it works great for 15min-1hour and then the sound cuts out, you hear a relay click off. If you turn it off and turn it back on, the chances are it will still be silent. If you turn the volume to zero, wait a few minutes and turn it on, it normally comes back and works again for a while.
You can fast-track the fault's occurence by turning the amp off while the volume is up, and trying to turn it back on while the volume is still up - it won't pass sound and not all the relays will open. If you turn if off and on with the volume down, it usually works fine (for 15mins-1hour).
Can anyone suggest where i should start looking on the schematic / what sounds like a likely culprit area? I have no idea where to even start with a fault like this!
Note - the protect light is NOT coming on when this fault happens.
Best,
Dave.
I'm afraid this amp has a new, exciting problem.
Here's what happens...
You turn it on, it works great for 15min-1hour and then the sound cuts out, you hear a relay click off. If you turn it off and turn it back on, the chances are it will still be silent. If you turn the volume to zero, wait a few minutes and turn it on, it normally comes back and works again for a while.
You can fast-track the fault's occurence by turning the amp off while the volume is up, and trying to turn it back on while the volume is still up - it won't pass sound and not all the relays will open. If you turn if off and on with the volume down, it usually works fine (for 15mins-1hour).
Can anyone suggest where i should start looking on the schematic / what sounds like a likely culprit area? I have no idea where to even start with a fault like this!
Note - the protect light is NOT coming on when this fault happens.
Best,
Dave.
First check would be for excess DC offset when the relay trips. Measure before the speaker relay, you should have no more than -/+100mv DC and normally far less than that.
The fault could be anything at this stage from a dry joint to an intermittent semiconductor and everything in between.
First step is to see what condition is causing the relay to trip.
The fault could be anything at this stage from a dry joint to an intermittent semiconductor and everything in between.
First step is to see what condition is causing the relay to trip.
Sorry for the delay - you called it once again Mooly. It was a cold solder joint on a capacitor on the tone board. I took the oppourtinity to adjust the idle current too and she's sounding sooooo nice 
. I'm starting to get concerned by your super human ability to diagnose audio amps remotely.
Thanks so much, have wonderful holidays.
. I'm starting to get concerned by your super human ability to diagnose audio amps remotely.Thanks so much, have wonderful holidays.
Pleased to hear you found the problem 
it comes from years of bench work. Practice practice practice.
And you
it comes from years of bench work. Practice practice practice. And you
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