DIY vacuum tube audio

[admin]

i am waiting for the first guy to build a triode based regulator for his lister power st head

maybe with a variable filament supply, low output power = soft filament glow
high output power = filament looks like a floodlight



ok, maybe that is going a bit too far?

nah!!!

admin

[clytle374]

I've seen a monarch(spelling?) lathe that has a DC spindle motor and the drive was tubes.  Talk about some huge tubes. 

Someone call up the guy that makes his own tube and see if he could do something with a couple old 50" CRTs. 

[rcavictim]

i am waiting for the first guy to build a triode based regulator for his lister power st head

maybe with a variable filament supply, low output power = soft filament glow
high output power = filament looks like a floodlight



ok, maybe that is going a bit too far?

nah!!!

admin

Well actually building an AVR for an ST type head would be practical and reliable plus EMP proof using gas or Hg thyratron tubes, and those have filament cathodes that glow, and glow from the ionization of the gas inside.  Thyratrons are sometimes called gas triodes and are the tube era equivalent of an SCR.
Another tube technology is the Hg ignitron.  Works a bit differently but the end result is an SCR type device with very low internal voltage drop.

With very low voltage drops the thyratron or ignitron tubes could replace the SS diode bridge in the field exciter circuit.  A suitable gate firing circuit would be required to trigger the thyratron/ignitron tubes at the proper phase angle.  Phase angle control is how conventional triac or thyristor light dimmers work.  The active device can only be in either on or off state, no partially conductive state like a resistor,  so they trigger the device to turn on at different level points along the AC sinewave to regulate the power level throughput.

[rcavictim]

This is OT for tube amplifiers but I had to build a spot welder a few years back to facilitate the manufacture of a large steel enclosure for an electrical device which I contracted to build.  The device worked by dumping a specified size of charge from a large capacitor bank into the work through a high current switch operated by a foot pedal.  I used a very large 3-phase industrial sized contactor with all three switch banks in parallel on the first attempt.  The first full power shot took 50% of the life off the contact surfaces in a blast of vaporized metal.  OK, try plan B.  I obtained a brand new water cooled ignitron tube and built a pulse trigger circuit for it operated ny the foot switch.  My little ignitron, the size of a 2 liter pop bottle could switch on a 20,000 amp DC current at up to several KV in micro seconds. This old tech was the perfect answer to my high current switch problem.  Unlike an SCR, I could not blow this ignitron up from reverse inductive surge and all the other things that kill solid state devices.  Tube technology rocks!

[clytle374]

My little ignitron, the size of a 2 liter pop bottle could switch on a 20,000 amp DC current at up to several KV in micro seconds.

Those weren't in any of the tube books I've read.  WOW.  Are there any of those still around?  Surely not manufactured anymore.   

EMP is a subject of interest, wanta start a thread on it? 

[cgwymp]

I have a tube handbook somewhere with those curves, so can figure out just what voltages to run where.

Let me know if you can't find yours -- I still have mine.  Same Sylvania book with the missing cover that you'd no doubt recognize.....  ;-)

[rcavictim]

My little ignitron, the size of a 2 liter pop bottle could switch on a 20,000 amp DC current at up to several KV in micro seconds.

Those weren't in any of the tube books I've read.  WOW.  Are there any of those still around?  Surely not manufactured anymore.  

EMP is a subject of interest, wanta start a thread on it?  

The ignitron I made the spot welder from is a NL-1062.  You can probaly google that and get specs.  Photo attached (sorry for the crappy quality).  I have two of these NIB except for limited use on one in my welder which never got it warm without water circulating.  They should still be available from National dealer Richardson Electronics.  Contact your banker and set up a second mortgage first. Ill try to get a better photo inserted when I can.

I just added a better photo of this wonderful poly alloy liquid metal metal SCR. 

[aqmxv]

My little ignitron, the size of a 2 liter pop bottle could switch on a 20,000 amp DC current at up to several KV in micro seconds. This old tech was the perfect answer to my high current switch problem.  Unlike an SCR, I could not blow this ignitron up from reverse inductive surge and all the other things that kill solid state devices.  Tube technology rocks!

You're reminding me of my favorite mercury vapor rectifier:

Its specs (from page 4 of this paper): 630V @ 111A.  These were the alternate source of power for the London deep level shelters of WWII - they rectified the 50 Hz line current to run all the critical systems.  In the event of failure of the mains current, the supply switches could be thrown to run the systems on Underground (London Passenger Transport Board) DC power directly.

See also this page, which seems to have another of the same Hewittic rectifiers

Let me know if you can't find yours -- I still have mine.  Same Sylvania book with the missing cover that you'd no doubt recognize.....  ;-)

I've got an RCA tube handbook that includes the 8417 curves - they're the hard-to-find part.  KT88 curves are everywhere.

[cgwymp]

Let me know if you can't find yours -- I still have mine.  Same Sylvania book with the missing cover that you'd no doubt recognize.....  ;-)

I've got an RCA tube handbook that includes the 8417 curves - they're the hard-to-find part.  KT88 curves are everywhere.

Good, 'cause after I posted I went to look at the 8417 curve in my Sylvania book and it's not on the shelf where I thought it was.  It's around here somewhere though -- no way I would have thrown it out!

[rcavictim]

aqmxv 

Here is a pdf file of all you ever wanted to know (again) about the 8417 including curves.

[aqmxv]

Thanks - I finally made it back over here and downloaded it.  Grad school while working has been sucking up lots of my time...

aqmxv 

Here is a pdf file of all you ever wanted to know (again) about the 8417 including curves.