SS power trans for tube experiments - 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 24th April 2007, 01:52 AM   #1
diyAudio Member
 
Join Date: Jun 2004
Location: Indiana
Default SS power trans for tube experiments

I have a rather large power transformer (weighs 6 lbs with large wire where I can see it) that was apparently intended for solid state. It has 39Vct, 30V and 13V secondaries. Is there any reason that I shouldn't use it for experimental tube circuits (low power) as long as I keep an eye on the core temperature? I am thinking of wiring the 30 and 39v windings in series to get near 100V rectified or using a doubler and then using wire wound resistors to drop the 13v winding for heaters.

mike
  Reply With Quote
Old 24th April 2007, 02:00 AM   #2
mach1 is offline mach1  Australia
diyAudio Member
 
mach1's Avatar
 
Join Date: Sep 2004
Location: Brisvegas
None whatsoever. However, you will be quite limited in the tubes you can use (a doubler should get you around 160V if your voltages were measured with no load).

pm
__________________
Au rutti wop-bop-a-loom-bop-a-boom-bam-boom - Richard Penniman
  Reply With Quote
Old 24th April 2007, 02:07 AM   #3
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Mike,

Bridge rectify the 13 VAC winding with 4X Schottky diodes. Filter with a large 'lytic and follow with a 7812 3 terminal regulator. You get NICE "juice" for small signal tube heaters.

Phase up the other 2 windings and connect them in series. "Full wave" voltage double into large value 'lytics. Follow the doubler stack with a choke and more capacitance. Think "extended" pi section filter.

The max. DC you can pull from the doubler is 0.25X the RMS capability of the composite rectifier winding.
__________________
Eli D.
  Reply With Quote
Old 24th April 2007, 12:30 PM   #4
diyAudio Member
 
Join Date: Jun 2004
Location: Indiana
Thanks guys. Very helpful!
mike
  Reply With Quote
Old 24th April 2007, 06:49 PM   #5
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
actually, i just finished designing a tube preamp that uses a 12V plate supply. low supply voltages aren't a problem with tubes if you are designing from scratch. with ltspice and the proper models, you can quickly find the optimum plate and cathode loads for low voltage operation. once when i was young i saw a tube breadboarding system that used springs (like the radio shack "300-in-1" kits) instead of fahenstock (sp?) clips..... the springs were much more reliable connectors than the clips(especially once you had more than 1 or 2 wires going to a connection). the breadboard kit came with a set of 1.5v filament tubes, a triode, a dual triode, a dual diode, a tetrode, and a pentode, iirc. the breadboarding kit also came with a 22.5v battery, and a 1.5v battery, and i think a 6v battery for grid bias...... so low voltage operation is nothing new with tubes..... the big difference that you'll find is that the current capability of that trannie will pretty much be wasted, since tubes rarely get over a few hundred mA for current draw (preamp tube plate currents are usually less than 10mA, and output tubes usually less than 100mA.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 25th April 2007, 02:50 AM   #6
diyAudio Member
 
Join Date: Jun 2004
Location: Indiana
My concern with running at too low of B+ is that linearity might suffer. I looked at the curves for 5687 and 6922 (the two tubes that I am most interested in at the moment) and just eyeballing it, it looks like it will be difficult to get reasonable distortion with less than 100V at the plate and even then the grid bias is only a couple of volts (headroom issue). I suppose choke loading the plate would help but then I just end up buying new iron for the choke instead of the trannie.

It seems like I should have enough transformer here to consider a voltage tripler. Of course that involves more componants also.

mike
  Reply With Quote
Old 25th April 2007, 03:44 AM   #7
diyAudio Member
 
Join Date: Apr 2003
Location: Portland,Oregon
Blog Entries: 4
Send a message via AIM to DigitalJunkie
I once did an experiment with a big SS amp transformer to see if it would work as a tube amp supply.I ran the ~100Vac into a trippler,and loaded it down with a bunch of power resistors..it held the voltage pretty well under load.I was surprised it worked so well,actually.
I think I used 1N5408's,and some 330uf 400V caps for the experiment.

I say why not,I think it could work well if you pay proper attention to the doubler/trippler stage. Use some big caps,and beefy diodes.
Old SS power transformers can be had for free/cheap,and they have tons of current available to feed a doubler/trippler circuit or whatever else.Plus,they usually an extra winding or two that could be used for filaments,etc.
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Power transformer for tube experiments ErikdeBest Swap Meet 0 7th March 2009 02:37 PM
Some experiments with switching power supplies Bootstrapper Power Supplies 17 22nd June 2008 11:03 AM
Experiments with an ATX power supply martinab2 Solid State 0 29th March 2004 10:04 AM
Experiments with power regeneration analog_sa Everything Else 3 26th August 2002 07:29 AM


New To Site? Need Help?

All times are GMT. The time now is 04:10 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