[SOLVED] Fresh build: 7805 is getting hot, device not turning on

[tmk009]

yes, i tried it with different usb sticks, all FAT formatted and different sizes/manufacturers.

When i put the USB Cable into a Computer, it says: "USB deactivated, the device is taking too much power blablabla..." and the preenfm is not turning on.
When i put in a regular 7,5V or 9V cable (with and without Jumper 2), the 7805 ist getting hot but still not turning on.

Not turning on means no signal of life at all: Display stays black. No LED is blinking, the USB stick led (if available, i tried different) is not blinking, nothing.

MEH

Any idea?

[Xavier]

When i put the USB Cable into a Computer, it says: "USB deactivated, the device is taking too much power blablabla..." and the preenfm is not turning on.
When i put in a regular 7,5V or 9V cable (with and without Jumper 2), the 7805 ist getting hot but still not turning on.
...
Any idea?

Seems like you have a shortcut somewhere that make the preenfm2 consuming a lot of current.
You could try first to clean a little the PCB from the yellow materiel that appear on the PCB when soldering. You can get rid of most of it with a small screwdriver, it's hard enough to crack and be removed.
Try to remove the ICs and OLED and check with "0 ohm beeping mode" multimeter for some shortcut between adjacent points.

[tmk009]

Ok. Looks like a job for this weekend 

[clément]

Same, I can not see any obvious thing sorry
There are a few soldering point that look kinda "weird" though, I would advice you to resolder any point that looks kinda like a ball, I'm sorry I don't have the time now to highlight those on your picture. Unless you're 100% sure of your soldering skills?
The yellow should come from the flux of your solder, mine produces quite a lot as well, it shouldn't be a problem but who knows, maybe it's hiding one!

[tmk009]

Yeah, I'm quite sure about the soldering, but I'll double check it! I just realized Xavier made these checking points for me. Great! I will at first clean it, resolder it, measure shorts with a beeper and then finally check the voltage.

I bet this is something stupid.

Thanks guys, read you in some days.

[Xavier]

I just realized you won't have the 2.5v if the preenfm2 does not boot.
And if there's a shortcut, there's good change everything is 0v.

Good luck

[tmk009]

Found it! It wasn't the pcb - there was a short at one of the display pins. I was too concentrated on the pcb though... Perfect. Let's check it out now! The encoder values are jumping a little, but this is a new problem to solve.

[Xavier]

Found it! It wasn't the pcb - there was a short at one of the display pins. I was too concentrated on the pcb though... Perfect. Let's check it out now! The encoder values are jumping a little, but this is a new problem to solve.

Congrats ! 
For the encoders, see the very last line of the doc :
http://ixox.fr/preenfm2/build-it/the-pcb-r5/
 

[tmk009]

Just want to let you know everything is fine now

[Xavier]

Just want to let you know everything is fine now

Great... thanks for the update.