Printer connects but doesn't communicate

I'm trying to set up my printer with Repetier-host 1.6.1 and can get connected ok, but no communication takes place. The board is a TronXY melzi type with repetier 0.91 firmware. Ubuntu reports a clean usb connection and 'lsusb' gives: "ID 0403:6001 Future Technology Devices International, Ltd FT232 Serial (UART) IC" which looks good.
The error message, in the toggle log, after the 40 sec timeout set in repetier host is "communication timeout - reset send buffer block"

As alternatives I've tried:-
3 different usb connectors
Windows 10 laptop
Every speed setting

Any suggestions?

Are you sure your repetier client is working correctly? Would try communicating with the printer directly through cura or some other program just as another check. I've also had failed firmware flashes if my usb chord runs too close the the printer power chords.

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If you need some help, or don't understand what I just said, feel free to send me a PM anytime

Printer: Prusa i3, 2 E3D v6 Hotends, Arduino + RAMPS 1.4 with a Bypassed 5V Regulator, 400w Insignia ATX PSU, Custom Designed Bowden Extruders

make sure you have matched baud rate of printer to usb on computer