I picked up a NAD C546BEE CD player for cheap because it wasn't reading discs and the VFD just displayed SERVO ERROR. The door would open and close but the disc would not spin up and the laser head would not move.
I was able to fix the problem. Will post it here to help anyone else who encounters a similar problem.
On the Servo Board there is a motor driver IC3 (MM1669XH) which has a "mostly" built in linear regulator; it just requires an external PNP transistor. This external transistor Q71 (2SB1457) has a 33 ohm resistor (R23) on the emitter. The collector of Q71 is the output of the linear regulator and provides clean power for a few different +3.3V rails.
The problem is that R23 is an 0603 size surface mount resistor -- just way undersized for this application. It had burned up and failed open, and the three power rails which should have been +3.3V were hovering around 1V. I tacked in a 33 ohm 1/4W leaded part and we're back in business.
I don't know what the current draw is on the three +3.3V rails but asking an LDO regulator to go from 8V down to 3.3V is a pretty big jump. And to put an 0603 resistor in that current path is really kinda kludgy.
Aside from that issue, the CD player is fantastic. Sounds good, super responsive, quiet mechanicals, built like a tank!
I was able to fix the problem. Will post it here to help anyone else who encounters a similar problem.
On the Servo Board there is a motor driver IC3 (MM1669XH) which has a "mostly" built in linear regulator; it just requires an external PNP transistor. This external transistor Q71 (2SB1457) has a 33 ohm resistor (R23) on the emitter. The collector of Q71 is the output of the linear regulator and provides clean power for a few different +3.3V rails.
The problem is that R23 is an 0603 size surface mount resistor -- just way undersized for this application. It had burned up and failed open, and the three power rails which should have been +3.3V were hovering around 1V. I tacked in a 33 ohm 1/4W leaded part and we're back in business.
I don't know what the current draw is on the three +3.3V rails but asking an LDO regulator to go from 8V down to 3.3V is a pretty big jump. And to put an 0603 resistor in that current path is really kinda kludgy.
Aside from that issue, the CD player is fantastic. Sounds good, super responsive, quiet mechanicals, built like a tank!
Attachments
I remember the good old day when I was more active with just fixing and modifying HiFi equipment of all sorts... The only sure thing with NAD was that it was.... going to end up in the electronics repair shop. Especially amplifiers.... those were notorious, suffering the exact same problems - overheating / heat dissipation and underspecified parts (transistors/resistors /Zener diodes) for the job.
Nice that you fixed it and thanks for sharing.
Nice that you fixed it and thanks for sharing.
Hello, I have the same problem and your analysis seems to be correct. After removing the board, I could see that probably also in my case the resistor R23 is burned out.
My question:
Duc say you replaced the resistor. But that is not so simple in purely practical terms. Did you drill 2 holes in the tracks and then solder the new resistor - or how did you do it?
Thank you very much for an answer.
o my God, thank you very much for this absolut quick answer:
But the picture is so pixelated that I can't make anything out.
What did you do?
Did you just "solder over" the resistor?
But the picture is so pixelated that I can't make anything out.
What did you do?
Did you just "solder over" the resistor?
Thank you for the quick reply.
I will try it out. It's worth the effort because I think the NAD 546BEE is absolutely fantastic.
I did the following yesterday as a little preliminary exercise:
I unscrewed the PCB, put my finger on the R23 resistor and concentrated on the resistor - how shall I say. Then screwed everything back together and tried it out: and lo and behold: it's been running flawlessly ever since.
I don't think I have any magical abilities, but I do find it amazing.
At the next malfunction - power steering error - I will replace the resistor.
Thanks again!
I will try it out. It's worth the effort because I think the NAD 546BEE is absolutely fantastic.
I did the following yesterday as a little preliminary exercise:
I unscrewed the PCB, put my finger on the R23 resistor and concentrated on the resistor - how shall I say. Then screwed everything back together and tried it out: and lo and behold: it's been running flawlessly ever since.
I don't think I have any magical abilities, but I do find it amazing.
At the next malfunction - power steering error - I will replace the resistor.
Thanks again!
The resistor's been running hot... the solder joints need to be touched up with a fine-tip soldering iron and a bit of solder.
ok, I will take note of that then.
Thanks again for the advice.
Without your thread I would now have to invest a lot of time and money ...
Thanks again for the advice.
Without your thread I would now have to invest a lot of time and money ...