4-65A Triode curves? - 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 5th January 2008, 01:19 AM   #1
diyAudio Member
 
dshortt9's Avatar
 
Join Date: Apr 2001
Location: Milwaukee, Wisconsin
Default 4-65A Triode curves?

Anyone ever try a 4-65A in triode? 65 watts Pd and 10 for G2 could give a 75 W dissipation for 15 or 20 watts SE. 600 volts allowable on G2. Always looking for the poor man's 300B.
  Reply With Quote
Old 5th January 2008, 02:58 AM   #2
diyAudio Member
 
astouffer's Avatar
 
Join Date: Jun 2004
Location: Pittsburgh, crumbling wasteland
http://www.curtcass.com/OTS/2003VSAC.html#vsac

Take a look at the 4th picture. I emailed the Oregon Triode Society asking if they could put me in contact with the builder. Sadly they never got back to me. Maybe you will have better luck.

The 4-65a is useless in tetrode mode so I always wondered about it triode strapped or even screen driven
  Reply With Quote
Old 5th January 2008, 03:06 AM   #3
diyAudio Member
 
dshortt9's Avatar
 
Join Date: Apr 2001
Location: Milwaukee, Wisconsin
Thanks for the lead. I'll try it and if I get some info I'll pass it along. Found a Mu of 5 g1 - g2 so that is in the ballpark. Might have to get one and light it up.
  Reply With Quote
Old 5th January 2008, 11:11 AM   #4
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Quote:
Originally posted by dshortt9
Thanks for the lead. I'll try it and if I get some info I'll pass it along. Found a Mu of 5 g1 - g2 so that is in the ballpark. Might have to get one and light it up.
I am using the 4-65A at present and have traced the triode curves on the tester up to 400V . 845 curves are close enough , Ra is around the 1.6k mark , mu of 5 . Currently running mine with James 6123HS at 530V/50mA , really these need to be run at around 650V / 55mA to get some decent power . Here's a pic of the Mk1 breadboard with T20 driver , it's totally different now and has LCL DC filament supplies , I would recommend implementing DC fils with all the big Eimacs with spiral filaments such as 100TH , VT127 and 4-65A . Also don't forget the heat dissipating caps !!!!!!

cheers

316A
Attached Images
File Type: jpg 4a.jpg (49.1 KB, 949 views)
  Reply With Quote
Old 5th January 2008, 12:21 PM   #5
diyAudio Member
 
rcavictim's Avatar
 
Join Date: Jun 2004
Location: Next to an open wormhole NW of Toronto
I have a bunch of 4-125A`s, sockets and associated parts pulled from some 500 watt transmitters (FRT-501). A bank of four in parallel ended up a PWM modulator to kick a magnetron for a radar astronomy telescope. These are an attractive radiation cooled tube. When the plates are glowing orange (permitted) they look very serious.

The 4-125 is similar to the 4-65A. just twice the Pd.

I have given some thought to a SE amp using this tube, so will follow this thread with interest.
__________________
On April 01,2012, my radioastronomy Project TARGET SETI search succeeded. The signal came via extradimensional subspace, not radio waves. I now get a lot of 'visitors'. I took my avatar pic of one friend watching me in my work yard from just 20 ft. away.
  Reply With Quote
Old 5th January 2008, 12:54 PM   #6
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Quote:
Originally posted by rcavictim
The 4-125 is similar to the 4-65A. just twice the Pd.

I have given some thought to a SE amp using this tube, so will follow this thread with interest.
I don't know about using the 4-125A as a tetrode but as a triode it's probably no good unless run zero bias . It will have Ra over the 2.5k mark and would require running the G2 way over it's 600V limit . Also think about the filament rquirements . I had problems getting the 4-65A quiet with AC . Tried different variations of hum pots , CT filament transformers etc and gave up and went to LCL DC filaments . The 2 x 8mH@10A input chokes , filament transformer and 2 x 30mH@5A isolation chokes added 18kg to the amp's weight .

cheers

316a
  Reply With Quote
Old 5th January 2008, 01:20 PM   #7
diyAudio Member
 
dshortt9's Avatar
 
Join Date: Apr 2001
Location: Milwaukee, Wisconsin
I had thought of using a 4E27A/5-125B but after hearing of your hum problems it might be harder than I thought. Someone posted triode curves of this tube showing an Rp of 1200. Perhaps using a HF switching supply would help?
  Reply With Quote
Old 5th January 2008, 02:00 PM   #8
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Quote:
Originally posted by dshortt9
I had thought of using a 4E27A/5-125B but after hearing of your hum problems it might be harder than I thought. Someone posted triode curves of this tube showing an Rp of 1200. Perhaps using a HF switching supply would help?
4E27 will have Ra around 2k as a triode . The Eimac datasheet specifies mu of 5 , gm of 2.15mA/V @ 50mA and I would expect similar as a triode at 500V . The 750V 20 watt G2 rating looks nice though I have no idea what switching power supplies sound like . Iron in the filament supply sounds good . I have plenty of iron but no SMPS so I'll stick to that for the time being Maybe I did something silly when AC filaments were tried . Try AC anyway but make sure you use an SG240 'surgeguard' on the transformer's primary

cheers

316a
  Reply With Quote
Old 5th January 2008, 02:00 PM   #9
diyAudio Member
 
rcavictim's Avatar
 
Join Date: Jun 2004
Location: Next to an open wormhole NW of Toronto
Quote:
Originally posted by 316a


I don't know about using the 4-125A as a tetrode but as a triode it's probably no good unless run zero bias . It will have Ra over the 2.5k mark and would require running the G2 way over it's 600V limit . Also think about the filament rquirements . I had problems getting the 4-65A quiet with AC . Tried different variations of hum pots , CT filament transformers etc and gave up and went to LCL DC filaments . The 2 x 8mH@10A input chokes , filament transformer and 2 x 30mH@5A isolation chokes added 18kg to the amp's weight .

cheers

316a

You are probably right that the 4-125A represens a challenge to fit into a practical audio amplifier. Of course this challenge, the journey as it were and the resulting esthetic beauty of transmitting bottles in your Hi-Fi setup are rewards some of us enjoy.

I have a pair of 450-TH`s here that just beg to be used in a monoblock subwoofer amp project!
__________________
On April 01,2012, my radioastronomy Project TARGET SETI search succeeded. The signal came via extradimensional subspace, not radio waves. I now get a lot of 'visitors'. I took my avatar pic of one friend watching me in my work yard from just 20 ft. away.
  Reply With Quote
Old 5th January 2008, 02:31 PM   #10
diyAudio Member
 
dshortt9's Avatar
 
Join Date: Apr 2001
Location: Milwaukee, Wisconsin
Thanks to all for the help! You saved me many hours and much greif. I may still try one of these tubes but you have shortened my learning curve quite a bit.
  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
Triode curves for 6AU5 boergars Tubes / Valves 8 24th April 2012 09:59 PM
7788 Triode Curves dsavitsk Tubes / Valves 89 21st July 2011 09:27 PM
814 triode curves ailouros6 Tubes / Valves 9 29th April 2009 05:04 PM
Derive Triode Curves from Pentode Curves? dsavitsk Tubes / Valves 3 14th May 2007 06:10 PM
6AK5 Triode Curves dsavitsk Tubes / Valves 2 29th March 2007 06:20 PM


New To Site? Need Help?

All times are GMT. The time now is 01:42 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