Anyone know what make of tube this is?

[mikeymike]

Hey fellas I was just curious if anyone had any ideas about who made this tube, it was in my 65 Fender Pro Reverb when I bought it.

I think it's an RFT but the plate only has one hole in the center instead of 3 running along it.

https://imgur.com/ZW89vi5






The tube says Amperex but made in GT. BRITAIN also marked with B6C1 and 66 with 31 under it

Because of the GT. BRITAIN I just assumed this was a Mullard but I've not seen any Mullard plates that look like these. They're sort of like fins with a single hole in the spine (RFT seem to have 3 instead of 1). Two 10 pointed micas and a getter ring at the top. The plates are smooth as well.

The images are linked and the imgur link itself has a gif that shows me rotating the tube slowly in pretty good detail

I hope someone out there knows what this is

[Vlada]

From construction point of view it seems like french made ecc81, but then B code doesnt make any sense
http://www.tube-classics.de/TC/Tubes/Valvo%20ECC81/ECC81.htm

[mikeymike]

hey Vlada, thanks for the reply. I didn't even think to look it up that way. It does kinda look like that one you are referring to. I think I have an RFT as well, it has 3 holes in the side but a similar fin plate design

https://imgur.com/Hs6PK7g

Curiously it is also marked Amperex and made in GT. Britain but the print is much thicker and more defined. The numbers are fatter on the side of the Amperex logo etc.

I honestly have no idea what these tubes are. This amp has some strange tubes in it.

[HotBluePlates]

... I think it's an RFT but the plate only has one hole in the center instead of 3 running along it.

Because of the GT. BRITAIN I just assumed this was a Mullard but I've not seen any Mullard plates that look like these.

I would assume Mullard Blackburn (indicated by the "B" in the printed code) until proven otherwise.  They look very much like many of the Mullard ECC81s in this gallery except with one hole through the folded side of the plate rather than 3.

The only reason RFT should be a thought is that a great many 12AT7 plates have a similar "single-wing" design, and RFT 12AX7s also have the same single-wing design and so look like 12AT7s at first glance.  But their mica spacers are entirely different & uniquely-RFT.

[Vlada]

I have a few British made ecc81, checked them today and all have 3 holes on the plate.  I asume it is french made but rebranded, which is not uncommon for philips made tubes

[HotBluePlates]

... I asume it is french made but rebranded, which is not uncommon for philips made tubes

I don't know that I have any French 12AT7s.  The very few photos I've seen have more-rounded corners on the plate (rather than box-style), and a central stiffening ridge.

So it's still a coin-toss between "French philips, but slightly different plate" or "British Philips, but fewer holes in the plate."  I don't know, so given the existing factory code on the tube, I'd tend to go with that.  Are you aware of any examples of a Philips-company tube having one code but actually being produced by a different factory?

There are a couple guys on other forums that tend to know all the details of different companies' tubes.

[Soulfetish]

Brimar

[HotBluePlates]

Brimar

Why Brimar, when they didn't use Philips codes on their tubes like this one has?

It has the Mullard Blackburn factory code, likely from March '66. 

Philips Factory Codes

[Soulfetish]

Brimar

Why Brimar, when they didn't use Philips codes on their tubes like this one has?

It has the Mullard Blackburn factory code, likely from March '66. 

Philips Factory Codes

Sorry. Should’ve read..
“Brimar?”