Hi at all, I recently purchase a DSO Quad from an ebay user.
I notice it work properly (I updated it right now without problem), but it doesn’t power on even with a good level of battery charge.
I can work with it only if the USB plug is connected, not with battery!
It seems to have some problem, maybe with battery charging, but I can always read the value Vbt=+4.18 when I switch on it with USB plug (even with battery disconnected 
!).
I think it very strange 
, any idea? Thanks in advance.
Disconnect the battery and check the voltage on battery.
Battery voltage is 3.72v, it seems to work properly. The red led is always OFF if I try to charge the DSO (as though the battery it was fully charged).
Check the voltage at pin 3 U19 and pin 4 U14 (cable USB disconnect).
I tried your suggestions and I found (first of all) 0V on any single pin of U14.
Then, I removed the metal plate and I found a strange position of battery plug, a bit tilted, so I tested it and… if I pushed to mainboard it, I could alway see the DSO power on .
Then I understood 
, the problem it was the battery plug on board.
I think that old DSO’s owner has done a bit of damage pushing the plug to connect the battery!
By some small soldering of plug pins of mainboard the problem was successfully solved 
!
I’d like to thank everyone for the support 
.