Originally Posted by NinjaHamster
Cool, thanks - I've also found some Philips PC88's which were manufactured in EI (Yugoslavia), apparently in 1987. So it is clear that I was wrong - there certainly were Amperexes (or Philips) tubes manufactured by non-Philips factories. You learn something new every day !
I haven't found any Amperex 6dj8's which were manufactured externally, but I'm still looking ... perhaps some of the later models ? Unfortunately there doesn't seem to be a huge amount of info on the Red Globes, which I think would be a likely suspect ...
Though some 6DJ8 were manufactured by other brands and then labeled for Amperex or other Philips brands, that tube type wasn't the most likely candidate for such a scheme in its early production days, since it was basically invented (or first made or whichever) by Philips in the first place. In Europe, Philips basically flooded the market with its numerous factories and brands, so Philips tubes - regardless of printed Philips brand - would have had a very high chance of being actual Philips tubes - regardless of actual Philips factory.
In the same time frame in the US, with the Amperex brand, you would probably find some degree of rebranding though, mainly of other US manufacturers. So, while in the 60s, in even moreso in the final tube days (70's onward), there was some rebranding going on, the 6DJ8 type isn't the best example of this, as far as Philips-group tubes go - but there was definitely some rebranding at times.
Actually, it's easier to find rebranded tubes the other way around, with Philips-group 6DJ8 & 6922 tubes being relabeled for other companies (either real companies or ones like "Beckman" or "Sonotone").
Here's an example I'd seen on ebay a few weeks ago:
EI in Yugoslavia is a slightly different example, as it wasn't exactly a "Philips factory" in the same way that the UK Mullard or French RTC factories were, or at least not in the same time frame (I forget whether it actually was a Philips-owned brand or just a Philips partner of sorts).
EI basically got the "old" Philips Holland machinery and kept making tubes with it in Yugoslavia until the war (some say after as well, but I've yet to actually see one of those tubes), so mainly in the 70's & 80's when the demand for tubes had diminished in most developed countries.
So, a Philips branded but EI made 6DJ8, while being a rebrand, kind of sits on the proverbial fence between being a Philips-group tube and a rebrand...