Need help (if possible) to understand why one Deskhop works fine and another one has a problem

[spanzetta]

I try to ask your help since you are the designer of this fantastic device.. (only you can help)

I built 2 identical device and while the 1st one works fine .. the other one has problems just with the keboard..

Of course I am using same cables/same keyboard/same mouse/same PCs..

When I connect the "problematic" one to the PCs (2 laptops) I see flashing the LED of both boards (2x Pico) but the keyboard simply doesn't work.. The mouse works and I can pass from one PC to the other one with no problem (and the corresponding LED becomes on)

I noticed that by putting some pressure on USB port of the keyboard.. sometimes make the keyboard working (have to keep the pressure) but then the mouse stops working.. If I remove the pressure from USB port again mouse works and not the keyboard..

I did check all the welding and all looks fine (of course the 1st thing I was thinking was a bad welding.. but it's not the case)

Since you know all details about the device.. what do you think can be the root cause of the problem?

Any further debug info or test I can do to provide you more info/details to better understand the problem?

Thanks in advance.. and again my big compliments for this fantastic project!

[spanzetta]

Tested with another set of mouse/keyboard (both standard/wired) and the problem doesn't appear..
Is it possible that there is a kind of (electronic component) "tolerance" problem where with a specific Keyboard one Deskhop works fine and another one not ?
I see no other explanation.. do you?

[hrvach]

Check the keyboard's power draw (usually specified on a sticker below). If applying physical pressure changes anything, maybe a cold solder joint or a broken trace somewhere? It would be helpful to provide pictures of the PCB, maybe that could suggest something.

When you plug in the "broken" keyboard, do leds flash back and forth?

[spanzetta]

HI hrvach, yes.. the leds flash back and forth.. but again after had tried with another keyboard eveything works fine..