EVO 1.3 128x32 board only has green power LED on and will not boot. Came from PCBway with 4 others that worked fine.

[action76]

 Tried many times and no luck. Could not get it to do anything past the green power light. Took it off the shelf the other day and my son thought the solder joint on 2940 looked suspect and touched it up. (no idea if it was bad or not)  We hooked it up and the pc recognized it.  We went into DFU mode and flashed it with ST DfuSe program. I took it home and put the LED panels on it and it booted up and I got the activation code and got the key put on an SD card with the color files.  I installed it in the machine and it is acting like it did before. Only the green power light and nothing on the LED panels at all.  Tried with and without the SD card.  Same result. I figure it must be a faulty solder joint somewhere but I do not see anything after several visual inspections.  Is there any componect I should look at closely that would cause this type of behavior?  Thanks for any help you can give me. 

Edited September 4, 2024 by action76

[action76]

I tested some components for voltage and found TS2940 to have 4.72V on the left leg and pretty much 0V on the right leg.  I saw another post from @Terranigma mentioning this part.  Does this mean that TS2940 itself is bad since it is outputting no voltage or (I don't think this would be the case but) would another component or bad solder joint cause it to not have any voltage on the other leg?

[Terranigma]

You can also check the voltages on the side of the TS2940 leg that is showing 0v to confirm it's not dropping down the 4.72v to 3.3v and supplying the other components. Also make sure you are reading it right, Pin 1 should be 4.7v~ in , Pin 2 is ground and Pin 3 should be 3.3v. 

 

If you aren't getting 3.3v on pin 3 and the other components after that are also not reading any voltage then it could be bad solder or a bad component. Check the connection and replace the TS2940 if needed.

[lucky1]

I would assume there is a short circuit on the secondary side causing the 3.3V pulled down to 0v.

This could be caused by either a defective component or a connection to ground .

[action76]

Thanks for the responses!  I replaced the TS2940 and now everything is working as it should.  I believe the component was faulty from the factory and when I heated it up to reflow the solder, perhaps it fixed the internal short temporarily, but failed again a bit later.  After the new TS2940 was installed it has worked beautifully.