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defect power supply AD2


Question

by a mistake a negative 20V signal has been connected to the AD2 scope input via the BNC-adapter booard GND line while it was connectd by USB to a deasktop computer !

Could this have destoyed the power supply of the AD2 ?  It doesn't operate in any kind now at any computer !

Can we try to repair / exchange some relevant parts of the power supply section (we have very experienced SMD repair specialists here) - can we gat a schematics + layout doc of the power supply section of AD2 ?

Thank you !

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Hi @HJM

In such case usually the FB19/FB18 burn out.
These are ferrite beads under the USB connector supposed to filter noise from USB.
Lets hope not other IC got damaged.

In the following post you can find troubleshooting tips, layouts:

 

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we replaced FB19/18 by a short - but nothing got better - the power consumption over USB is about 300mA (as should be), but not sign of life is shown - the only hint I can give, is that the IC shown on the attached picture got very hot - can we get the schematic/info of this part to replace it ?

AD2error1.thumb.jpg.f4988f0c6115474a8c9a74032f3268c2.jpg

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Hi @HJM

The device initially should take less than 100mA and 300-400mA after software connection.

The mentioned hot component is IC48 for AUX supply voltage windowing:
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#usb_power_control
Its abs max rating is 6V.

You can remove this, the device should function without it.

image.thumb.png.86b6fa9d961805a3d31dad4673d3148a.png

 

The IC20 has 6.5V rating, this may be damaged too.

 

In case the device is not detected by the computer you should verify the USB controller rails.

 

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thank you attila for your real good support - but the sugggested repair has not shown any positive result - as I already assumed for this kind of error, there must be affected a lot of circuits by the -20V coupled to the GND line (the lab power supply may have delivered up to 2 A until shut-down) and this may have killed something hidden !

Fortunatly the price of the AD2 module is quite affordable - so we will buy a new one (as in principle it is a really got device for some tests) - perhaps we will try to connect it to the PC over an USB isolator (can you recommend a specific brand that you have succesful tested?)

Best regards and thanks again HJM

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Hi @HJM

Sorry to hear that the device is badly damaged.

I have only tested cheaper USB FS isolator (ADUM4160).
Such will reduce the data transfer rate (from 20-40MBps to 1.5MBps), the capture rate (from 100/s to 25/s) and record/play rate (from 1MHz to 100kHz), but the device is still usable.

 

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