12FQ8's ? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 18th April 2005, 03:46 AM   #1
Trout is offline Trout  United States
diyAudio Member
 
Trout's Avatar
 
Join Date: Nov 2004
Location: Midwest Madman
Question 12FQ8's ?

So, today I picked up this wurlitzer organ at an auction.

Open her up and start looking for useable tubes.

28 pcs 12FQ8's RCA Date coded 63-17 all test great on my P.O.S national professional tester.
Are these good for anything other than where I got them?

Twin Double Plate Triode's

Really pretty looking tubes anyways, Labeled wurlitzer Made by RCA In usa Shiney black plates. Orange labeled.

Gene
  Reply With Quote
Old 18th April 2005, 03:59 AM   #2
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
Hmm FQ8? FQ7 would be a 12V 6CG7, but 8...hmm I'm guessing something like 12DT8 maybe, but a taller envelope?

Lesse...

http://www.mif.pg.gda.pl/homepages/f...93/1/12FQ8.pdf

Hmm, whoa, one cathode, two grids, four plates? Wild stuff!

12AX7-ish gain, but a 12AT7 curve. Not terribly linear, not much current, but good gain. Could use it in a phono I suppose.

Would be good for splitting a signal in two with no crosstalk. Take one triode and use two individual plate loads, coupling to whatever circuits as needed. One can't effect the other. Well, in theory that is. I wonder how the plates interact?

- Any idea what it was used for in inside the organ? Oscillator perhaps? The extra plate would allow tapping a Hartley osc. without pulling it too bad...

...28 pieces? Probably main oscillators then. Maybe four harmonics (=octaves) in one tube? Flip-flop dividers, or does each plate have an LC tank?

Oh, and if you say something looks nice... you MUST supply pics.

Tim
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote
Old 18th April 2005, 04:01 AM   #3
Trout is offline Trout  United States
diyAudio Member
 
Trout's Avatar
 
Join Date: Nov 2004
Location: Midwest Madman
Quote:
Originally posted by Sch3mat1c
Hmm FQ8? FQ7 would be a 12V 6CG7, but 8...hmm I'm guessing something like 12DT8 maybe, but a taller envelope?

Lesse...

http://www.mif.pg.gda.pl/homepages/f...93/1/12FQ8.pdf

Hmm, whoa, one cathode, two grids, four plates? Wild stuff!

12AX7-ish gain, but a 12AT7 curve. Not terribly linear, not much current, but good gain. Could use it in a phono I suppose.

Would be good for splitting a signal in two with no crosstalk. Take one triode and use two individual plate loads, coupling to whatever circuits as needed. One can't effect the other. Well, in theory that is. I wonder how the plates interact?

- Any idea what it was used for in inside the organ? Oscillator perhaps? The extra plate would allow tapping a Hartley osc. without pulling it too bad...

...28 pieces? Probably main oscillators then. Maybe four harmonics (=octaves) in one tube? Flip-flop dividers, or does each plate have an LC tank?

Oh, and if you say something looks nice... you MUST supply pics.

Tim
OOOps,

Yep,, I beleive ocilli's, They were divided up into 3 banks/chassis all labeled.

This thing had a really weird compliment of tubes, 9 GE 12ax7s, 3 6EU7's, 1-6U4, 1 - 6AU6 and a couple 7868's on output.
2- 12 inch instrument speakers, and some kinda mechanical leslie thingy with 2 about 5 inch speakers, reverb tank,, and a humdity control heater??
HUGE power tranny!!!! must be 15 lbs of iron lol
Gene
  Reply With Quote
Old 18th April 2005, 04:07 AM   #4
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Looking at the data sheet, it's not too different than a 12AX7, but it does have nice low interelectrode capacitances. And a nice, high 330V max plate voltage suggests that it could be a very nice tube for an input diff amp for a power amp.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 18th April 2005, 04:24 AM   #5
Trout is offline Trout  United States
diyAudio Member
 
Trout's Avatar
 
Join Date: Nov 2004
Location: Midwest Madman
Heres a Pic of the tube, Sorry bout my poor camera skills, We just bought this new cannon and havent mastered it yet lol
Height and diameter of the tube is the same size as a 12AX7. internally of course is very different.

Click the image to open in full size.
  Reply With Quote
Old 15th July 2008, 03:25 AM   #6
diyAudio Member
 
Aud1073cH's Avatar
 
Join Date: Feb 2008
Send a message via AIM to Aud1073cH
Default Resurecting the thread - any more input?

I found a Wurlitzer organ with these tubes too. (possibly the same model?)

someone had already stolen the 12AX7's at the thrift store before I got it but I only paid $1.
Because it was missing so many parts, and in pretty bad shape, I parted it out right there behind the store in about an hour.
Saved what tubes were left (mostly 12FQ8, some 6EU7), what sockets I could, as well as many of the switches, speakers, vibrato unit, spring reverb unit, and swell pedal.

Has anyone got any schematics that use the 12FQ8 tubes? Is a wah possible with these tubes? I don't have much experience building things with tubes yet.
  Reply With Quote
Old 15th July 2008, 03:59 AM   #7
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
The 12FQ8's are probably the frequency dividers. Some of them may be used as oscillators as well. Look for a pot or trimmer cap that is used to tune the upper octave (12 notes) of the organ. These will be connected to the oscillators. Each oscillator's frequency is divided by two to generate the next lower octave, and divided again for the next octave. Each twin plate triode can generate two different divide ratios when used as a triggered relaxation oscillator. The time constant is set up to be just a little longer than the desired repitition rate and a trigger pulse is applied to the grid. It is possible to build a multivibrator that runs at two frequencies at once (related by a factor of two) using one of these tubes.

Way back in the late 60's I had a Baldwin organ that used 36 6SN7's in the tone generator circuit. 12 were oscillators and 24 were frequency dividers. It had a huge power transformer, but most of the size was because of the huge filament requirements to light all of the tubes. I eventually sold it, but figured out how it worked, and built my own version using RTL IC chips from scrap PC boards (in 1970). The organ no longer exists, but I still have those hand wired boards.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 15th July 2008, 04:20 AM   #8
diyAudio Member
 
Aud1073cH's Avatar
 
Join Date: Feb 2008
Send a message via AIM to Aud1073cH
I don't have the organ anymore, but it did have the tubes arranged in banks, and each bank had an adjustment that read "tune to G" or whatever note that bank was.

I do love modular stuff. Could I make an LFOs or VCO's with these? Or perhaps a suboctave guitar effect?
  Reply With Quote
Old 15th July 2008, 04:37 AM   #9
diyAudio Member
 
astouffer's Avatar
 
Join Date: Jun 2004
Location: Pittsburgh, crumbling wasteland
Go to your local library and try to locate a book called The Electronic Musical Instrument Manual. The earlier the version the better because once you hit the early 70s copyright a lot of tube stuff was removed. Its a must have for anyone who wants to make noise with tubes.

If anyone has the opportunity to acquire a Novachord don't pass it up! Listen to the samples near the bottom of the page

http://www.discretesynthesizers.com/nova/intro.htm
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 12:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2