Analog Discovery 2 Oscilloscope Channel Measuring -25 V

[nieran]

Hello,

 

I have an Analog Discovery 2 that has had an issue on Channel 2 of its oscilloscope for a few months now. Essentially, the channel measures around -25 V at all times, whether it is floating, grounded, shorted, connected to the BNC adapter board, etc. I have not used it in any high-voltage applications or scenarios. 

I have attempted to manually recalibrate the oscilloscope, but I get an error when I do so telling me the voltage on Channel 2 is between -2.7418 and -2.7412 V but it should be around 0 V. I've attached a screenshot of this error below. Note that I did calibrate the Wavegen 1 offset as suggested but that did not fix the issue.

I've also tried loading the factory calibration, which seemed to load successfully but didn't resolve the issue. When I measure the DC voltage on 2+ pin on the AD2 I see it's around -4.8 V, whereas the 1+, 1- and 2- pins all read around 0 V. 

I'm happy to probe around more to help debug, but for now I'm not too sure where to start.

 

Thanks,

K

 

[attila]

Hi @nieran

Probably the ADG612 on the 2nd channel (toward the middle of the board) is damaged due to high voltage.
 

https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#scope_input_divider_and_gain_selection

See C2 ADG612: