Fysetc S6: 5V rail drops to 4.4V when attaching USB

Drachenkaetzchen

Note: Posting in complaints as there's no S6 forum yet.

I have received my new S6 board a few days ago. I power the board via an external +24V PSU. Once I plugin the USB connector, the +5V rail drops to +4.4V. No current is being drawn via the USB port. For testing purposes I have only connected +24V to the board, as well as the USB plug.

Here without USB plugged in, 5.15V average.

As soon as USB is plugged in, Average drops to 4.47V.

For a future revision, I recommend a jumper to select between the internal +5V switchmode supply and USB. This also allows users to supply +5V themselves.

eliwong_git

Drachenkaetzchen
Thanks for your feedback, I also found this problem in recent tests.
The original purpose of designing USB5V is to facilitate the programming operation for customers. Although it is convenient, it also brings some problems. We will take your suggestions to replace this part of the circuit.

trevjonez

this issue is present on the v1.2 S6?

I am thinking that it may be causing my display to have lower contrast making it hard to read off angle at all.

I will measure and see if true, as I am running klipper firmware I can not disconnect USB in normal operation.

Additionally it seems tmc drivers need to have the 24v come online before 5v so disconnecting power from USB would be good to ensure a connected raspberry pi doesn't cause issues there.

I am thinking a possible workaround would be to modify the cable used to cut the 5v line, or remove the F5 fuse from the PCB.

trevjonez

just measured and confirmed it drops on the v1.2 pcb. when shutting down the attached raspberrypi the lcd brightness jumps up to where it should be.

I think I will go ahead and trim/clip the power wire in my cable.

EDIT: yea cut the 5v line on the usb cable and the LCD is great now.

dinamitemic

Hi guys, same problem here but if I put a piece of tape on the 5V on the USB plug the board is not detected anymore by the raspberry.

GeorgeFu

There is topic about this : https://community.octoprint.org/t/octoprint-doesnt-detect-printer-in-usb/21100