I have had the oscilloscope for a few months. First time I managed to charge it ok and use it. Now I tried to charge it again using the USB cable connected to a) A USB mains adaptor from my HTC phone (5V, 1A) and my laptop. In both cases the charging led does not turn on and there is no perceptible charging taking place. I measured the output voltage from the USB cable and it is only 5.02 V - not 9 V. Does this mean the USB cable is faulty?
After reading the manual, it seems possible to charge through USB.
In the manual it states that it can be charged through a USB port.
However it can take up to 7 hours and you can not use the scope while it’s charging.
Most machine when you turn them off it will shutdown the USB ports as well.
It would be best to use a 9 volt adapter.
You may want to change the cable you are using.
Ok, I didn’t read the manual 
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Manual states that the charger should deliver 500 mA… so it is best not to use a long USB cable unless it has an exceptional quality.