Just reading all the posts (that I missed) shows that many people are suffering from this problem with the C390DD. I have replaced all electrolytic capacitors on the PSU-B board. After measuring them all, there were several that had a reduced capacitance by about 10%, but there was one that was really dead: The 47 uF / 400 V directly after the rectifiers. That would be the first one to look at. But since I have had start-up problems since the beginning when it was still new, I dived a bit deeper and have added three components to improve start up behaviour. This was inspired by information I found on the Power Integrations website, the supplier of the used ICs. More details in attached document. Hope it helps.
Hi Henk. Thank you very much for sharing your analysis and solution for this issue. I will look into this and will see if I can get it to work. May take a while for me to report back with my results.
Reading further into this, I think your previous startup problems are different to my startup problems. It seems when you had this issue, when you attempted to turn your amplifier on, you would get a relay click and it would not get much further then that (If I have understood correctly). That would lead to your deduction that it was an issue turning on the 12.5v supply.
The issue I have and some others have is more minor in that using the remote to power on sometimes has no result (no relay click). Pressing the power "on" on the remote a second time (or maybe a third time) is usually sufficient to get the amplifier to turn on completely. Kind of like the IR receiver circuit needs to be woken up before it will accept the "on" command. So in this case I would think the 12.5V supply is not involved, and the issue is occurring earlier in the startup process. Perhaps an issue with the 5v standby, or 12V supply, or the IR receiver circuits.
Hi Nugaluk, You are right. My problem was more severe in that the amplifier did not switch on. Pressing the power button at the front made the LED go from orange to blue, and that was all. If I remember correctly even the display remained blank. Until yesterday I never used the remote to switch on the amplifier. After reading your posts I tried a number of times with the remote, but it seems to work fine.
It's a pity that NAD/Lenbrook seems to do a lot of cost cutting by using cheap passive components, even for expensive equipment. If they would use Panasonic or Nichikon elcaps I think that there would be far less issues. If you do some searches on the internet for NAD reliability, it makes me reluctant to buy NAD again. Too bad. Especially amps like the M10, the M33 and even more the M32 seem to offer fantastic specs and features. But if it only works for a few years, then it isn't very attractive.
It's a pity that NAD/Lenbrook seems to do a lot of cost cutting by using cheap passive components, even for expensive equipment. If they would use Panasonic or Nichikon elcaps I think that there would be far less issues. If you do some searches on the internet for NAD reliability, it makes me reluctant to buy NAD again. Too bad. Especially amps like the M10, the M33 and even more the M32 seem to offer fantastic specs and features. But if it only works for a few years, then it isn't very attractive.
Yeah I agree. They make gear with great features and specs but after replacing all the crappy capacitors in my c390dd, I would never buy NAD gear again. I do like this amp though so I hope I can keep it operational.
Hi everyone and a happy new year.
This is my first post in the forum, as I have zero skills at DIY and what brought me here was this thread. I own a C390DD that has the same issue that was this thread's raison d'etre. Namely, it won't turn on from stand by (a relay sounds, orange led turns to blue, but nothing else happens). Like Henk's unit, it behaved like this from time to time, and eventually turned on after a few tries - until it didn't.
The amp is at the NAD service here in Athens, Greece for some time now. The technician there swears that the problem is not with the power supplies, but with the main board - possibly the processor chip, even though there is no way to be sure. As it was too expensive a part to just buy blindly on a hunch, I found a used board on eBay (from a very respectable repair shop) but that didn't work either.
The technician gave up on the amp and I'm picking it up unrepaired. I am going to try Henk's solution anyway, but do you think the main board might indeed be the culprit, as the technician claims? Any similar experience/ideas?
This is my first post in the forum, as I have zero skills at DIY and what brought me here was this thread. I own a C390DD that has the same issue that was this thread's raison d'etre. Namely, it won't turn on from stand by (a relay sounds, orange led turns to blue, but nothing else happens). Like Henk's unit, it behaved like this from time to time, and eventually turned on after a few tries - until it didn't.
The amp is at the NAD service here in Athens, Greece for some time now. The technician there swears that the problem is not with the power supplies, but with the main board - possibly the processor chip, even though there is no way to be sure. As it was too expensive a part to just buy blindly on a hunch, I found a used board on eBay (from a very respectable repair shop) but that didn't work either.
The technician gave up on the amp and I'm picking it up unrepaired. I am going to try Henk's solution anyway, but do you think the main board might indeed be the culprit, as the technician claims? Any similar experience/ideas?
Hi Eyebee,
Based on the age and the same symptoms it is very likely the same problem with the power supply B. I expect the problem with the official NAD technician is they probably only swap in replacement boards rather than replacing components on the board. So if they can't get a replacement power supply board from NAD they can't do anything.
If you are comfortable opening up the unit to have a look, you may even see that some of the capacitors on the power supply B are bulging which indicates damage. You may even find extra capacitors that are failing in addition to just the ones listed in the original post. If you are comfortable with replacing capacitors yourself you can replace the ones on power supply B and any others that look bad. Otherwise you might be able to find a technician that can replace the capacitors on the board for you. You may also want to try the solution mentioned by Henk which is a modification, though perhaps just replacing the capacitors will be sufficient?
If you are attempting this yourself please be very careful as there are dangerous high voltages involved.
Good luck and hope you report back on your progress.
Based on the age and the same symptoms it is very likely the same problem with the power supply B. I expect the problem with the official NAD technician is they probably only swap in replacement boards rather than replacing components on the board. So if they can't get a replacement power supply board from NAD they can't do anything.
If you are comfortable opening up the unit to have a look, you may even see that some of the capacitors on the power supply B are bulging which indicates damage. You may even find extra capacitors that are failing in addition to just the ones listed in the original post. If you are comfortable with replacing capacitors yourself you can replace the ones on power supply B and any others that look bad. Otherwise you might be able to find a technician that can replace the capacitors on the board for you. You may also want to try the solution mentioned by Henk which is a modification, though perhaps just replacing the capacitors will be sufficient?
If you are attempting this yourself please be very careful as there are dangerous high voltages involved.
Good luck and hope you report back on your progress.
Hi Nugaluk,
Thanks for the advice. I have already left the amp at a local electronic repairer's, along with the link to this thread and Henk's uploads. He will change the capacitors before trying Henk's mod. I had opened the amp when it first bricked, but I'm not experienced enough to tell whether any caps were bulged as they weren't too obviously damaged. Anyway, I will let you know whatever happens. Whatever chances there are for the amp to work, they're there thanks to the invaluable input of all of you.
In the meantime, I have my fingers crossed!
Thanks for the advice. I have already left the amp at a local electronic repairer's, along with the link to this thread and Henk's uploads. He will change the capacitors before trying Henk's mod. I had opened the amp when it first bricked, but I'm not experienced enough to tell whether any caps were bulged as they weren't too obviously damaged. Anyway, I will let you know whatever happens. Whatever chances there are for the amp to work, they're there thanks to the invaluable input of all of you.
In the meantime, I have my fingers crossed!
When i tested the 12 volt rail for some reason it measured between 0.5 volts and 0.7 volts. Is it possible that there is a problem with the PWM circuit itself when injecting 12 volts to the amplifier board itself the led lights up as normal and the 5 volt circuit is functional as the relay does click when the power button is pushed
This is the simple soulution for the power on failing/black screen issue. The value of the capacitor is crucial or there may be oscilation problems. I've used a low ESR Panasonic FR series as this was the only capacitor I had at hand at this size. 47uF/50V. This will ensure enough impedance versus the TL341 at the higher frequency that will make the curcuit "sing".
Further I've seen people only removing DW201 diode with good results. Lower temperatures and no power on problems. This diode is not on the schematics either(?). I've opted to not do this.
Further I've seen people only removing DW201 diode with good results. Lower temperatures and no power on problems. This diode is not on the schematics either(?). I've opted to not do this.
Attachments
And to add further more, the 431 will be stable when the Vca/Ica is sufficiently high. Therefor, no need for more complexity than to just add a 47uF capacitor. If we read the Texas Instrument paper on stability, they state a capacitor range lower than x and higher then y. Y being 10uF. But they have later Said that 10uF may not be enough and right on the threshold. The reason for using 47uF, is to take ageing into account.
I've owned this amplifier for 11 years. It started not powering on about 7 years ago. I responded by leaving it on 24-7 which worked well until now. Unfortunately it recently it got turned off and would not restart. I've replaced all of the suggested and bulging capacitors in PSU-B to no avail. I have not yet attempted the Henk / Johnips solutions of additional capacitor.
As an alternate (much more cowboy) solution can I just use another 12.5V or 12V power supply to juice directly into the wiring for the cards that use 12.5V? Looks like just a few lines on the 12pin connector J203 and the 4 pin connector J205.
As an alternate (much more cowboy) solution can I just use another 12.5V or 12V power supply to juice directly into the wiring for the cards that use 12.5V? Looks like just a few lines on the 12pin connector J203 and the 4 pin connector J205.
Attachments
You should change all capacitors, and especially the ones close to heat sources, and not to forget the high voltage one. And please do add the capacitor as described above. This is a design flaw in my opinion.
There are two circuits almost identical. Only the one needs an additional capacitor.
This amp is a real gem, and should be fixed.
There are two circuits almost identical. Only the one needs an additional capacitor.
This amp is a real gem, and should be fixed.