Ask them, not sure they will provide schematics, or ask them under an non disclosure agreement ? or maybe just the input section
Or provide us with pictures of the board, we can help identify some chips, normally you have some coupling chips or maybe some who do somekind of isolation ??
Thank you for your reply.
I asked them right after my post here, but saying the truth, not sure if it was a good idea. I got an auto-reply that says they are going to answer in 24h. If I get some sort of negative answer, it is a good idea to ask just for input section, thanks fot that.
About the pics there are plenty of them at this forum thread:
https://www.eevblog.com/forum/testgear/sainsmart-dds120-usb-oscilloscope-(buudai-bm102)/and here with detalis of some IC's:
https://sigrok.org/wiki/SainSmart_DDS140but don't worry about it, I have already checked the IC fuse, the IC LDO 3.3V, all diodes and some transistors. Next I need to unsolder some transistor for proper test but first I prefer so see if I get the schematic.
On wednesday I am to receive my new oscope Siglent SDS1202X-E (
https://www.siglent.eu/sds1202x-e.html)
once having it I could make some more advanced checks like some OA's that could be acting as isolation, as you said.
Thank you again.