Help Diagnosing NAD D7050 Boot/Firmware problem as seen in this old thread

[Iceberg]

Hello, this thread details the same behavior I have with my NAD D7050.

My DAC just died :-(

Hi, So I've had a NAD D7050 for close to 10 years and it just died. I'm quite sad about it as I really like everything about it from its look to its quality. Anyways, would welcome advices to help pick a replacement as I completely lost track of the recent innovations. I'm on a budget, and all...

www.audiosciencereview.com

I am starting a new thread because they didn't solve it, and the thread went into selecting a new unit.

I'd like to make a go at fixing this, if anyone would like to help.

From what I am seeing, I am able to load new firmware via network, and its successful. Then for a second the unit works and its starts to tick (relay type sound) and tries to restart. I do see the main screen which I would expect for just a brief instant, then flickers a bit and ends up to what looks like simply shutting down.

The service manual is linked. I will work on it and update as I find new things. This looks solvable.

firmware guide: https://nadelectronics.com/wp-content/uploads/2016/09/TD2013-05-D7050.pdf

service: https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Nad-D-7050-Service-Manual.pdf

 

[Doodski]

Hello, this thread details the same behavior I have with my NAD D7050.

My DAC just died :-(

Hi, So I've had a NAD D7050 for close to 10 years and it just died. I'm quite sad about it as I really like everything about it from its look to its quality. Anyways, would welcome advices to help pick a replacement as I completely lost track of the recent innovations. I'm on a budget, and all...

www.audiosciencereview.com

I am starting a new thread because they didn't solve it, and the thread went into selecting a new unit.

I'd like to make a go at fixing this, if anyone would like to help.

From what I am seeing, I am able to load new firmware via network, and its successful. Then for a second the unit works and its starts to tick (relay type sound) and tries to restart. I do see the main screen which I would expect for just a brief instant, then flickers a bit and ends up to what looks like simply shutting down.

The service manual is linked. I will work on it and update as I find new things. This looks solvable.

firmware guide: https://nadelectronics.com/wp-content/uploads/2016/09/TD2013-05-D7050.pdf

service: https://www.vintageshifi.com/repertoire-pdf/pdf/telecharge.php?pdf=Nad-D-7050-Service-Manual.pdf

I went through the service manual. Lots of IC's, some pesky digital transistors and multiple PCB's. It might be possible to try diagnosing the power supplies, audio circuitry and such. Overall though It might be a replacement item. Do you have a background in trouble shooting circuitry, do you have a O-scope and a proper multimeter? If you do have experience this is going to be a tedious diagnosis due to the nature of the fault/complaint. There are only short moments to dynamically troubleshoot circuitry so it might purely be a case of troubleshooting with the power OFF and shot gunning it. Look for protection circuitry and the associated IC pins that sense the protection circuitry and ensure all voltage regulation is measuring well.

 

[Iceberg]

I went through the service manual. Lots of IC's, some pesky digital transistors and multiple PCB's. It might be possible to try diagnosing the power supplies, audio circuitry and such. Overall though It might be a replacement item. Do you have a background in trouble shooting circuitry, do you have a O-scope and a proper multimeter? If you do have experience this is going to be a tedious diagnosis due to the nature of the fault/complaint. There are only short moments to dynamically troubleshoot circuitry so it might purely be a case of troubleshooting with the power OFF and shot gunning it. Look for protection circuitry and the associated IC pins that sense the protection circuitry and ensure all voltage regulation is measuring well.

I'm an electrical engineer, albeit out of practice. I have all the necessary lab gear.

I think the behavior can diagnose the problem for about 90% into where to start looking. On the surface, the unit seems to function correctly when given stimulus:

-networking functions, admin page works
-display works
-power supply output looks good

When you run the firmware upgrade, it seems to follow the process correctly.

The amp seems to "boot"

Then the clicking noise, which to me indicates some kind of protection, or some kind of overload, or who knows right now.

The end result after the ticking and booting is that the unit is back to its original state of "bootload" when powered on but will follow the process again if you start it.

Something is happening right on or after startup that is sending the unit into some kind of reset, and only loading firmware seems to get it operational. It might be simplistic to say that something is being wiped, but that kinda seems like the behavior.

Also, did u get it to work with a usb stick? Did u need to prep it? I get "error" when testing this via usb.

 

[Iceberg]

Does anyone know what these acronyms mean? OVC? Over volume? Over voltage? And VOV?

I get the feeling this could be the root cause if all output circuits are turned off until a boot cycle happens, that means pre-boot everything works ok, but once it boots output circuits get turned on and the problem happens. Just a theory. Not elegant, but "bootload" may be some type of protective behavior end state.

 

[Doodski]

I'm an electrical engineer, albeit out of practice. I have all the necessary lab gear.

With your skill level and extensive knowledge I am sure you can diagnose and repair if it is not requiring proprietary IC's or other unavailable parts.

The schematic is not a totally friendly layout (Not like a nice one page color layout Sony schematic that's for sure. ) and so this could get convoluted pretty fast. Check the protection circuits to see if it is going into protection after the relay(s) engage. The protection stuff is located in differing regions of the schematic pages and snippets of them so you might want to magnify and print out the schematics and make notes so you don't go in circles. I could give you more suggestions although in the end you are going to have to do the nose to the grindstone thing and do this logically so you can avoid loosing orientation and repeating measurements and going in circles. I can't say much more without being there personally. It would be helpful if you can as step 1 disassemble the until and thoroughly visually inspect all sides of the PCB's using a magnifier and then power it ON with the unit layed out on your workbench for easier access to both sides of the PCB's. Watch for those digital transistors, they do fail, sometimes they crack from heat and can be seen to have failed and when trying to measure them with the meter when the unit is not powered ON is virtually fruitless unless de-soldered and or looking for shorts. As per the various IC's look for crystal oscillators (I counted ~6) and ensure they are oscillating upon startup, check for grounds and regulated voltages at the IC's and watch for zener diodes that may have failed. I hope this gets you headed in the right direction.

 

[Doodski]

Oh... and do a good visual inspection of and meter the capacitors. They are high failure items too.

 

[grahamrex]

Any luck here? I have the same issue. Unit working fine for a decade, and then when I turned on recently the Display is stuck showing "Bootload". I logged a ticket with NAD, but they said trying pressing reset button 20 times . Which did nothing. They guessed the reset button was stuck. Feels to be working fine to me. I wasn't able to get the firmware to update via the USB (couldn't figure out how to connect via network - maybe someone can help me with that).

I'd love to fix as not looking to upgrade, but not sure it is worth sending off to service centre as could get expensive if it fails again (had it repaired under warranty in first 18months)

I have opened the cover (was not easy) and tried visually inspecting the reset switch, but not sure what I am looking for. Also, tried disconnecting ribbon of reset switch (or at least that is what I am guessing it is) - no longer showed bootload, but unit remained in standby and wouldn't turn on.

Not technical, but good at following instructions. I have a multimeter, but a novice at using it. Up for giving things a try as otherwise it's destined for the recycling

 

[kerns]

@grahamrex Same issue! Wish I could have it repaired. /cc @Iceberg

 

[alxppp]

I had the exact same issue and it was a blown C204 capacity (service manual part name). Replaced it with a Panasonic 10V, 1000uF with 10Kh operating life and it's working like a charm.