There are times you have to run a stand-alone 710US without the
wall power supply, but you may notice it doesn't work as smooth as
Why does a non-standalone 710U work perfectly powered by a PC's USB
port alone, while a stand-alone 710US only works sometimes when the
wall power supply is not used?
The secret is in the power section of the device. 710U and 710US
shares the same PCB, but 710 US has its wallpower
circuit populated. To protect the PC's USB port, diode D5 has
to be added to the USB port's power path. As the result, when the power
output from the USB port is low, the volotage-drop from the diode will
reset the 710US.
So, if you have to run 710US as 710U, without the wall power supply,
move the jumper on JP16 from position 2-3 to 1-2 to bypass the
Note: Please make sure you move the jumper on
JP16 from position 1-2 back to 2-3 to include the protective diode
when you are done with such situation.
Make sure your DI-194 is not a simple rectangle shape, otherwise it is an older version
of DI-194 and the following does not apply.
1) Remove R24 (100 Ohms)
2) Install diode D6
3) Install R25, the following value should be OK:
If it is between 10V to 15V, R25=1KOhms
If the voltage of the external power supply is less than 10V, R25 =330Ohms
4) Apply the external power to DI-194 via Dig 0
No need to do anything with Q3 and JP3