Newproduction power tubes: Reliablity

is there a question in your post?

No, Its a statement of belief,, = that china is not well know for relaible, musiacl sounding tubes, Sorry to say, when it comes to tubes (except in SET tubes) china Loses.
I have Psvane 12AX7 in nice beautiful boxes, = lose to every EU NOS tube/every USA tube, 
Russian EH pre tubes are wonderful. vs china. 

e GL KT88,

Tried em, didn't like them, return to vivatubes
Much prefer the Svet new 6550's, the new plant uses the exact same equipemnt as the burned down plant, 

NOS Svet 6550 = New Production Svet 6550, exact same tube,

I've used KT150s for the past couple of years without issue

Ok this is what we need to hera,, and would make sense the KT150 are in fact reliable, as jadis uses this tube in stocking a  few of their amps, jadis would never (except in the choice of EI KT90s wayyyy back when= mistake= bad tubes)  employ unrelaible tubes. 
Thing is, I did not care for the 150 in my amp. 
Almost damaged the Defy7,, as a  150 will not work in that circuit.

chinese tubes have historically had a reputation for cheap manufacture and poor qc - back 10-15 years ago they were truly grim

russian makes have had their problems too

in both cases, quality has improved a lot... 

the chinese in general are state of the art in making things cheap, run on the hairy edge, and have failures... they have value engineered the world's supply of most everything, but such is way of capitalism and commoditzation

russian makes still have some soviet military mindset, make things more to last, thicker glass, more solid metal structures inside

this being said, the chinese and russians now also very much understand there is a good size market for quality - so in tube making, they have responded with higher qc, higher quality materials, made premium products as a result and of course they charge accordingly... that is good for us pursuing this hobby/activity

still, i buy from known sources who do secondary testing, i do not trust factory testing in and of itself yet - i won't buy from cheapest ebay sellers without a long reputation

as mentioned, when a power tube fails there is often secondary damage to associated equipment... so it is not just about the seller of the tube taking the tube back - they won't fixed your damaged amp...

"Much prefer the Svet new 6550’s, the new plant uses the exact same equipemnt as the burned down plant,

NOS Svet 6550 = New Production Svet 6550, exact same tube, "              Wrong!      All New Sensor Corp got from the Svetlana Co was the name.      The St Petersburg plant, where their =C= tubes were manufactured, burned down and took the equipment with it (a shame).       Currently; The New Sensor tubes are actually manufactured at the former Reflektor plant (X-pul factory), in Saratov.       You may have conflated the rumor, concerning Mullard’s equipment, that this page mentions, with SED/Svetlana’s: https://www.effectrode.com/news/rubble-ruins/