Of course I tried it and there are no tamper seals. But just because it seems to work doesn't necessarily mean it's working properly or going to keep working as it is. Or maybe some setting i try in the future doesn't work. Although since this is related to the USB connection that's probably unlikely.
Ah, ok, you did test it, good. From your initial post it really didn't read that way, especially when you were talking about 'just returning it or trying to repair it'.
I didn't expect the board to be fully populated, there are lots of other areas not populated. The only reason I was curious about these two resistors is the pictures you originally posted show these two in place and it is the 1022I model if I'm not mistaken. All the iso chips are populated and I believe you confirmed it was the 1022I model in your post.
My mistake - it was actually me who added those resistors (and forgot). I like to provide a discharge path, even on Isolated equipment, if only to avoid the risk of static buildup. I used 2 x 10M resistors if I remember correctly. Purely a personal choice though.
I have ordered Chinese electronics that have had loose/extra parts and balls of solder rolling around inside. Lots of poor soldering and cold joints as well. There is also a ton of counterfeit product floating around. Then there's real product that's supposed to be trashed because it failed QC but ends up going out the back door of the factory. Then someone does a shoty repair or just sells it and you end up with a sub par product. I just wanted to make sure everything looked ok and it looked like a legitimate board before plugging the thing into my USB port.
I'm glad to say that no one appears to have counterfeited the Owon, there probably isn't enough margin in it. They are pretty keenly priced given the BOM cost. I though you said you had tested it before taking it apart, that would imply plugging it into your USB port.
I understand your motivation though.
Thanks for your reply though, on closer inspection it does appear its intentional. Hopefully it was the Owon factory that did the mod. I'll do some tests and post back if I have any issues.
You're welcome, I hope I haven't put you off posting here, we're generally a friendly bunch (even me
). Yes that would be a factory mod. Owon do seem to be pretty skilled (or at least cunning) in their board mods. On my earlier rev board they managed to correct a swap in the USB signals by diagonally crossing two 0603 resistors on adjacent pads - something that would be taxing one-off, let alone on a production line!
P.S. I've just seen your trace captures, yes that looks nice, no cause for concern there. I think you'll be happy with it. If you're still worried about noise performance then you could try replicating some of the tests that I carried out for rf-loop on page 1. Hopefully yours, being a later rev board, might be quieter still.
...and yes, the UI is surprisingly good (especially for Owon, who've taken some flack previously). You might want to look at the shortcuts I identified too.