I can only review stuff as I see it in front of me
Sure, nobody is asking for more, all you can do is check/test what in front of you. When there are issues you might (or might not) call manufacturer (or who else provided it) to get answer or replacement (or nothing, which is as well an answer). You can as well call other customers of that particular
object-of-discussion to double check, but on the other side this happens automatically (everybody who can will double check own unit for x or y issue, only lazy idiot would ignore problems).
This are your reviews, so your opinion is what counts (during and immediately after review). Any other (later) comments from others are important as well, but only when they really important (double checked item/result related and not only blah blah blah or what so ever rant). Follow-ups (from you or other qualified testers) are of course important as well.
This unit was NOT hacked, it was a direct factory replacement.
I did run the internal calibration procedure to verify that wasn't it.
What more was I supposed to do?
well, Tekway/Hantek haven't provided any replacement, Charles as well. So this was all you could do. Everything else was done by other users (and this is why i said "ignorance").
That DSO hardware is using lot of techs what need to be calibrated. There is e.g. table (actually set of text files/tables) which contains factory cal information. This can
NOT* be restored/run/created by enduser. The self calibration is taking values from factory cal tables, so when they already fucked up, the resulting self cal will be fucked up as well. Both manufacturer don't want to provide informations how the factory cal need be executed (and exactly necessary/where to measure), not even to large distributor (or better said his cal lab) under NDA.
What Charles got was a replacement board. All he was capable to do was to insert that board and run self-cal, nothing else. When there was something wrong in factory cal, Charles** was not able to fix it. Sure, there is a way to check the whole DSO, but honestly when asking for replacement you would expect that the manufacturer know what to do and what to provide. And that's the problem here. I can't speak for others, but almost every time i asked for replacement, i got DOA or not calibrated boards. No idea if this issue has been fixed, i can only speak from what i observed between 2009 and 2012.
I will see, when i got some spare time, i will "destroy" the factory cal and make some screenshots showing what kind of wired results the DSO is showing without or with wrong cal. Charles probably run some simply tests, which is of course all he have to do because the manufacturer have to provide
working repalcement board, and after he saw waveforms jumping on the screen he released for sell that unit back as "working".
* I have reversed their procedure as far i was able to do, one thing (non linearity of frontend part) is still not reversed (but at least Hantek told me what the unknown params means, and here to look for it). As long no physical changes done to frontend, the factory cal procedure i published can be used to restore DSO. This, together with the schematics i drawn and posted was even enought to build own DSO clone based on the information provided by me. If there is someone, except the few engineers on manufacturer side, in the worlds knowing these DSO then me. I'm not a fanboy, i spend as well lot of time on other DSO in the same price range (Rigol, Siglent, Tonghui, UNI-T), not only for testing but as well reversing of hardware and software. If there was something ugly, i always asked manufacturer first to fix - when no response or taken too long - i published my "comments"/rants and possible solutions.
** i don't now Charles and what he is doing (or not), but as said above, nobody is expecting not working replacement parts. sure, DOA due transport damage, but that's all. Hanek/Tekway however, as many other chinese manufacturers as well, have problems to understand what QC means. If you wan't to know more about specific manufatcurer, check their website. If there are boken links, they you know all you need to know. Typos or chinglish are OK, that didn't means anything about quality, but broken links are no go.
Talking about one-off issues, well, maybe the Rigol PSU you tested have does have such one-off issue, but honestly, as long not prooved i and other can rant on it (exactly as you did on other one-off things). Few µs 4V peak is no go for me, as i said, nobody knows it there are no other issues/peaks.
And that's why I showed it!
and this is exactly what we all expect, if there is something, show it!