Dead V2 on USB only
Plugged my V2 in today to USB, and one of the lights came on, but the screen did not come on...windows said "unrecognized device, or there is a problem with the device".
Worked fine yesterday.
If you plug it into an OBD port, it powers up fine, but still wont communicate with a PC in pass-thru mode...so there is something wrong with the USB section.
I opened up the V2 and did some probing around, looks like the ground pin on the USB connector doesnt have a very good ground connection with the ground plane on the V2's circuit board. The ground pins on the RJ45 connector for the OBD port have 0 ohms to the ground plane on the PCB, so thats fine, but the USB connector shows about ~40 ohms pin to ground plane. I tested all of the pins/connections on the "data line protection" chip, the ST USB61, since it was the first thing that goes to the USB connector. I looked up the datasheet for the USB61 and figured out what readings should be...and it looks like something is wrong with the trace between the USB connector and the GND pin on the USB61.
Also, I was only reading about 3.9-4.0v on the V2 (probing the Vcc pins of various chips on the board) when powered up via USB. I assume the thing works on 5v and not 3.3v.
I wasnt sure if there was supposed to be any resistance, if there was some capacitor or something in the USB ground to V2 ground plane...but since the RJ45 ground from the OBD port is tied right to the internal ground plane of the V2, I figured there was a problem with the USB connector.
So I figured I had nothing to lose (my V2 is probably 8+ years out of warranty) so I shorted the USB ground pin directly to the V2's ground plane, plugged it in, and now it works perfectly!!
So my next step is to desolder that USB61 chip and see if theres some bad connections, or a bad trace where it passes underneath the USB61.
Ill report back my findings, but I figured I would post up my temporary "fix" if someone else is having a similar problem. Obviously do this at your own risk, and dont do it if you dont have soldering experience and electronic circuit design knowledge... I just needed my V2 today for important work and dont have time to send it off to be fixed.
Ben
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