RCA voltage regulator - 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 6th September 2008, 07:09 PM   #1
diyAudio Member
 
astouffer's Avatar
 
Join Date: Jun 2004
Location: Pittsburgh, crumbling wasteland
Default RCA voltage regulator

Has anyone ever built the 250vdc voltage regulator in the back of later RCA tube manuals? I tried breadboarding this but it doesn't work well at all. Not much regulation and R5 dissipates a lot of power when the pot is turned down (output voltage goes up). Anything look wrong with the schematic?
Attached Images
File Type: jpg rca voltage regulator.jpg (79.3 KB, 709 views)
  Reply With Quote
Old 6th September 2008, 07:42 PM   #2
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
I don't like it. Too complex, and this is one of those situations where KISS applies. Here are a couple of hollow state active regulators I designed and built. This one is a rather conventional design adapted from a solid state regulator. The 6CB6 small signal pentode is a high gain device with an unusually high Vhk rating that makes it convenient for error amp duty. It works just fine, and holds its output voltage to 0.8V for a rail change of 40V. The project it's in has been in operation since December, 2005 and the output voltage hasn't moved at all in that time.
Attached Images
File Type: gif screen-reg.gif (9.5 KB, 705 views)
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 6th September 2008, 07:49 PM   #3
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Here's a somewhat different version. For this, the 6KE8 triode/pentode type operates as a cathode coupled error amp. The voltage gain section is the pentode, another high gain type. The triode section couples in the reference voltage. This allows the inclusion of an RC LPF to reduce noise and to take a load off the voltage reference tube. This would correspond to the noninverting input of an op-amp. It's a bit more complex, but it operates just as good as the simpler version. This one also hasn't shown any signs of drift over time.
Attached Images
File Type: jpg screenreg.jpg (29.5 KB, 637 views)
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 6th September 2008, 08:55 PM   #4
diyAudio Member
 
astouffer's Avatar
 
Join Date: Jun 2004
Location: Pittsburgh, crumbling wasteland
Thanks for the schematics Miles. It looks like my ignorance of how the design actually works is showing. Varying the load resistor does indeed keep the voltage steady, however varying the input voltage causes the output to change. R5 is underrated on the parts list. It dissipates 2w with 250v out.

This is for a small PP pentode amp. I found a nice design from Sound Practices using a 6BM8 to regulate the screens. This larger regulator is for the main B+. Using a regulator seems like a more elegant way to drop some excess B+ voltage.
  Reply With Quote
Old 6th September 2008, 09:19 PM   #5
kmaier is offline kmaier  United States
diyAudio Member
 
kmaier's Avatar
 
Join Date: Jul 2007
I wouldn't say it's complex, it's a classic regulator circuit that dates back over 50 years and can be found, along with others (including screen regulators), in ARRL manuals from the 1950's. I built this circuit over 30 years ago (my Dad built it over 50 years ago) and it performs well. Also note that it has a specific input voltage from 325 (full load) to 375 volts (no load) with a specified output of 250 volts. Have you exceeded the input voltage? What is your target output voltage?

Note that you can re-bias it, but pay particular attention on the 5651 tube. This is NOT a shunt regulator but a voltage reference tube and has a narrow operating range from 1.5ma to 3.5 ma (max) and should be targeted around 2.5ma average current. If you have good tubes and good layout it should work fine.

Regards, KM
  Reply With Quote
Old 6th September 2008, 09:45 PM   #6
diyAudio Member
 
Geek's Avatar
 
Join Date: Sep 2004
I've used a small-tube variant of Miles' screen regulator and it's pretty much the defacto for regulated supplies now. It's a good one

Cheers!
  Reply With Quote
Old 6th September 2008, 10:19 PM   #7
diyAudio Member
 
korneluk's Avatar
 
Join Date: Jan 2005
Location: South Florida
Quote:
Originally posted by Geek
I've used a small-tube variant of Miles' screen regulator and it's pretty much the defacto for regulated supplies now. It's a good one

Cheers!
what are some typical component values?

TIA,
  Reply With Quote
Old 7th September 2008, 05:59 AM   #8
diyAudio Member
 
Geek's Avatar
 
Join Date: Sep 2004
Here's the schematic for the one I did:
http://geek.scorpiorising.ca/GeeK_Zo...p?topic=3665.0

Maybe Miles could provide info on the ones he used?

Cheers!
  Reply With Quote
Old 7th September 2008, 06:12 AM   #9
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
I currently use couple of 120V Zeners in series and one IRF730 as a voltage follower. More than enough for screens of 4 tubes GU-50 and couple of preamps/phase splitters.
__________________
"Our youth [...] have bad manners, contempt for authority; they show disrespect for their elders, contradict their parents, [...] and tyrannize their teachers.” -- Plato, 447-367 BCE
  Reply With Quote
Old 7th September 2008, 06:15 AM   #10
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
For the regulator with the 6KE8 error amp:

C1: 1u0
C2: 0u033
C3: 0u1

R1: 470R
R2: 4K7
R3: 60K / 2W
R4: 50K / 1W
R5: 200K
R6: 6K8 / 5W
R7: 1M
R9: 6K8 / 2W
R10: 139K
R11: 25K (Multiturn cermet)
R12: 136K

The design isn't quite so easy as the solid state version where you always know that Vbe= 0.6V all the time. So you use loadlines as you would for any other aspect of hollow state design to set Q-Points and determine component values.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  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
voltage regulator Sebastiaan Power Supplies 2 12th June 2005 07:51 PM
Voltage Regulator ! jleaman Power Supplies 11 13th May 2005 12:00 AM
Voltage Regulator zoro72 Everything Else 0 26th April 2004 05:30 PM
Voltage regulator help! kasra Solid State 7 23rd November 2002 02:07 PM
What voltage regulator to use? Thomas Everything Else 2 28th September 2001 02:53 PM


New To Site? Need Help?

All times are GMT. The time now is 12:46 PM.


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