Mystery tube in a Fisher FM-90X - V50,064

[john q. bebop]

I recently received a Fisher FM-90X, dirty but it works great, nos tubes and all. One of the tubes listed on the chassis and in the schematic is designated as a "V50,064". I can't find any data on this, any ideas what it is?

[G]

Originally posted by john q. bebop
I recently received a Fisher FM-90X, dirty but it works great, nos tubes and all. One of the tubes listed on the chassis and in the schematic is designated as a "V50,064". I can't find any data on this, any ideas what it is?

Can you post a pic of the tube as it is mounted in the amplifier? That may help.

[gingertube]

Fisher FM-100 manual here:
Its not the right model but MAY help.

http://www.mcmlv.org/Archive/HiFi/FisherFM100B.pdf

Cheers,
Ian

[Tom Bavis]

It's covered in Sams Photofact folder 407-8 - you might compare that one if you're looking at the Fisher schematic. Not in my collection, sorry.

What does this tube look like?

[john q. bebop]

After checking out the schematic for the FM-100 from gingertube's response I came up with this, an Amperex (or Valvo) 6922 PQ, late 50's.
It has the gold pins & pinched waist described in this link: http://spazioinwind.libero.it/themag..._waist_eng.htm
The only markings on the tube that I can read is the "52F", which you can see in the picture. There is a fainter marking that I think is "46L" but I'm not sure. Maybe a date code?
What do you think?

[john q. bebop]

I forgot to add in my description earlier that this tube also has a "D" shaped getter instead of an "O" shaped getter.

[gingertube]

Looks just like every other 6DJ8/ 6922 I've ever seen. I'm sure you are right.
Cheers,
Ian

[john q. bebop]

You know, I checked out the Sams Photofact and it listed the tube as a "v50064" Ha!

A 6922 it is then. Thank you for you help in identifying this tube, I appreciate it. Now I know what to shop for if I need a replacement.

The tuner is neat by the way.

[BFNY]

Originally posted by john q. bebop
After checking out the schematic for the FM-100 from gingertube's response I came up with this, an Amperex (or Valvo) 6922 PQ, late 50's.
It has the gold pins & pinched waist described in this link: http://spazioinwind.libero.it/themag..._waist_eng.htm
The only markings on the tube that I can read is the "52F", which you can see in the picture. There is a fainter marking that I think is "46L" but I'm not sure. Maybe a date code?
What do you think?

I can verify for sure it is a late 50's Amperex 6922 Pinched waist.
This is the "cascode" tube in the Fisher Golden Cascode circuit. It was an innovative RF amp circuit that was also used in many later Fisher tuners. I also have an FM90X here. Funny thing, I bought it a long time ago, and then bought some Amperex 6922 pinched waist tubes (cheap) to use as exact replacement spares. Many years laterI find out this is the holy grail tube for many people, worth big $. :-)

Bob

[john q. bebop]

BFNY,
Thanks for the positive ID on the tube & the info on the circuit. Surfing' the web I couldn't believe how much those tubes go for.
It's a cool tuner and in glorious mono no less!