I have a NAD t743. It was new when purchased by us, so must be 12 or more years old by now.
It worked fine until we leant it to someone. I understand they just stored it without using it for a year or two. We then grabbed it back and noticed the following issues.
1. The unit works fine when cold, allowing you to select inputs and change settings. However, as it heats up the screen starts to go funny and the unit is no longer responsive. Eventually the screen goes and stays black.
2. The fan does not trigger automatically. I've tested the fan with an external 12v power sources and the fan works.
3. The unit seems warmer than it should be for what it is doing (driving two main speakers with some music, not very loudly). I've circled the area in hte attached image (image was borrowed from another website, can't find the credit for it at the moment).
This unit sits in my shed and I really just want it to recieve stereo RCA input from my laptop to play music. I can work around it at the moment as the input is always the one I want, so I just quickly set the volume to zero before it goes funny, and then use my laptop to control the volume level.
My gut feel is that the thermistors / thermocouples used by the software are faulty and giving funny readings. This might explain why it appears to go into a standby mode and why the fan doesn't trigger. But it never says 'overheat' like it should, and the unit keeps playing.
I've given the unit a thorough clean with the aircompressor to remove any dust that I can.
Keen to hear anyone's thoughts on all of this.
(I've seen the other t743 threads but nothing much in there related directly to what I'm seeing here)
It worked fine until we leant it to someone. I understand they just stored it without using it for a year or two. We then grabbed it back and noticed the following issues.
1. The unit works fine when cold, allowing you to select inputs and change settings. However, as it heats up the screen starts to go funny and the unit is no longer responsive. Eventually the screen goes and stays black.
2. The fan does not trigger automatically. I've tested the fan with an external 12v power sources and the fan works.
3. The unit seems warmer than it should be for what it is doing (driving two main speakers with some music, not very loudly). I've circled the area in hte attached image (image was borrowed from another website, can't find the credit for it at the moment).
This unit sits in my shed and I really just want it to recieve stereo RCA input from my laptop to play music. I can work around it at the moment as the input is always the one I want, so I just quickly set the volume to zero before it goes funny, and then use my laptop to control the volume level.
My gut feel is that the thermistors / thermocouples used by the software are faulty and giving funny readings. This might explain why it appears to go into a standby mode and why the fan doesn't trigger. But it never says 'overheat' like it should, and the unit keeps playing.
I've given the unit a thorough clean with the aircompressor to remove any dust that I can.
Keen to hear anyone's thoughts on all of this.
(I've seen the other t743 threads but nothing much in there related directly to what I'm seeing here)
Attachments
I will have to look at the rails and get back to you. To be honest, I wouldn't know where to start looking on the board. i have the service manual so I will do some reading and work i tout.
The issue seems to occur before the fan would normally come on, i.e it only takes a few minutes, even in really really cold weather. Also, running the fan from the external power source from start up does not prevent the issue from occuring, though it does delay it a little.
Have you had any luck trouble shooting or fixing it at all?
It seems to get abnormally hot for what it's doing, even when idling. I've blasted the dust out of everywhere I can reach/see, so maybe a short is occuring somewhere?
The thermal fuse is embedded in the mains power supply, so no joy getting to it.
Can confirm that it's the problem though; just YOLO'd and bypassed it, now my unit is fine. Using a temperature controlled fan to vent the enclosure and trigger the internal fan. Might wire up a proper thermal fuse for safety later.
Can confirm that it's the problem though; just YOLO'd and bypassed it, now my unit is fine. Using a temperature controlled fan to vent the enclosure and trigger the internal fan. Might wire up a proper thermal fuse for safety later.
FYI, sorry to resurrect an old thread but I did find a way to harvest the power amp side of my receiver and play some music with it.
After doing some trouble shooting, the V+/V- seem good, but the secondary AC voltages that go and drive all the brains are all reading low. I suspect that's where the issue lies. For now I have bypassed it all and am injecting a signal directly into the amp board and it sounds just like it used to.
Details here:
NAD T743 - converted to analogue stereo power amp
After doing some trouble shooting, the V+/V- seem good, but the secondary AC voltages that go and drive all the brains are all reading low. I suspect that's where the issue lies. For now I have bypassed it all and am injecting a signal directly into the amp board and it sounds just like it used to.
Details here:
NAD T743 - converted to analogue stereo power amp
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