Fualty Duet wifi 2

aaf4

I have followed that guide twice now with no luck. I can not see any damage to the board.

I have some basic electrical knowledge including some semi basic pcb assembly for my model railway including a cbus system. The hot processor is suggesting its been damaged somehow and I can only think of a short somewhere.

aaf4

Ok. I have been through my wiring again with a fine tooth-comb and can not find any shorts anywhere. I have double check all connections and again can not find any 24v or even 5v shorts to the 3.3v rail.

What else could be causing this?

dc42

If the processor is getting hot then it has probably failed. Is anything else getting hot? Check the WiFi module, SD card, and U11 in particular.

The most common cause of failure is a short in the wiring between +3.3V and a higher voltage, or between +5V and a higher voltage. Shorts like this usually blow multiple components, in particular over-voltage on the +3.3V rail usually blows the SD card and the WiFi module first, and then the processor after that. Over voltage on +5V typically blows U11 and often the 3.3V regulator too.

The processor can be replaced, but it may not be worth replacing it if other components have failed too.

aaf4

@dc42 I can only check by touch as I have no other tools available.

The regulators are cool to the touch. The wifi module and sd card reader are warm only but can easily be held. The processor can only be touched for 3-4 seconds.

Hope this vaguely helps

A Former User

can you measure the voltage on the 3v3 rail?

elmoret

Not normal for the processor to get that hot, likely was exposed to a voltage over 3.3v.

aaf4

@smece 3.32v

A Former User

@aaf4 that's weird, if the 3v3 rail is 3v3 the 3v regulator is probbly ok and possibly rest of the chips on 3v3 rail are ok so maybe just replacing the mcu will get the board up and running

aaf4

Is there any other test I can do? At the moment its looking more and more like a processor failure.

The board is less than 1 year old. Only purchased in July last year so confused as to why the processor has failed. There seems to be no other evidence of a short as everything which should have failed first is still working.

Please can someone advise the best option to get this card operational again as I need the printer in the very near future.

Thanks

A Former User

@aaf4 said in Fualty Duet wifi 2:

Please can someone advise the best option to get this card operational again as I need the printer in the very near future.

dc42 suggested replacing the cpu, "anyone" with some practice and hot air station can do this. A hacker/maker-space or phone repair shop might be able to do the job if you supply board and part. Or practice and DIY.

dc42

@bearer said in Fualty Duet wifi 2:

dc42 suggested replacing the cpu, "anyone" with some practice and hot air station can do this.

To expand on that, there are two ways that I know of:

Use a temperature-controlled hot plate (I use a cheap electric hot plate + multimeter with thermocouple attachment to monitor the temperature), hot air desoldering station, and a vacuum pickup tool (very cheap on eBay, but some of them leak). The pickup tool is needed to remove the large chip without damaging the PCB traces or disturbing adjacent components.
The alternative would be vacuum pickup tool, ChipQuik or similar low melting point solder, and solder wick (to remove bridges after you resolder it using a soldering iron and solder).

There are plenty of videos on youtube showing how to do this. Whichever method you choose, practice on an old hard disk drive or similar first. Or find someone else who has done it before.

I have only used method #1. My first two attempts failed because I didn't have the pickup tool. Since then I have done two successfully.

HTH David

A Former User

@dc42 said in Fualty Duet wifi 2:

ChipQuik or similar low melting point solder

This stuff is amazing. I use cheap generic Sn42Bi58 ($5/100g) melts at 138C, works a treat.