KT88?

[mathewf]

Can anyone identify this valve please? It has KT88 scratched on the side and tests similarly to a KT88 but is unlike any KT88 I've ever seen - certainly doesn't look like a GEC, Genelax or Tesla and too old to be of the modern crop.

It has 2 round getters on top and black plastic base, similar hight to a KT88 but slimmer.

Any ideas anyone?

[kheper]

The bases are different, but it looks like a 7535.

[kheper]

7535 (and other codes) are probably a variant of the 6550. They may be later production (late 70s-early 90s) of 6550 like tubes.



They seem to fetch a high price even if used:
https://www.tubeworld.com/6550.htm

6550A (42W PD) would be my guess:
http://www.mif.pg.gda.pl/homepages/fran ... /6550A.pdf

The 6550 has only 35W PD, so scratching KT88 on it makes sense.

[Geek]

6550 variant, huh?

I've seen those on the bench in vintage no-name-brand guitar amplifiers. I just thought they were EL34 knockoffs and replaced them with EL34
(none came back )

[kygeezer]

Those are probably Sylvania (and later, Philips) 6550 judging by the internals (two top getters and one side) and straight sides, smaller diameter than the GEs. They were rebranded RCA (who never made a 6550 of their own) and others. I had some that were some generic brand and labeled KT88 that were Sylvanias. The only 6550s made in the US were GE, Sylvania, and TungSol.

[kygeezer]

Well, I got side tracked looking at all the metal based tubes! The original pictured tube has a bakelite base, so it is not a Sylvania. Could it be an early Russian 6P3E or similar? I once bought a few "5AR4s" from a foreign seller, and they were 5Y3s, some relabeled 5AR4 and some showing the faint 5Y3 label as well.