EL41 PP power supply questions - 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 13th January 2012, 08:15 PM   #1
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Default EL41 PP power supply questions

Hello community, I have plenty of these old rimlock socket tubes and I was planning building this little amp.
Click the image to open in full size.

I'm wondering what's the purpose of the cathodes connection to the S7 filament winding mid tap , is it for hum reduction ?
Also why is the filament winding for EZ40 connected to the +B and why is it using a separate winding S6 (I'm guessing it's the 5V for type 80, although the EZ40 has 6V filament).
What about the power transformer voltage S5 ? the usual 2x 375V 100mA would do ? apparently the plate of EL41 is rated for 250v max. Any advice ?
Click the image to open in full size.
  Reply With Quote
Old 13th January 2012, 08:29 PM   #2
diyAudio Member
 
Join Date: Aug 2010
Location: Near Eindhoven, the sanctum of the pentode. and among that other things.
Send a message via Skype™ to v4lve lover
the 6.3 volt winding connected to the cathode of the rectifier tube suggests it has separate live windings . this deals whit the issue of rectifier cathode breakdown . ive had cases where i was shocked by the AC fillament supply

much safer to use diodes . but that is my biased opinion .

the other winding seems to be the heather winding . EG there is a common cathode resistor wich shares ground whit the chassis and the center of the heater supply much like a hum pot . this does not matter as there is now only little potential on the heater windings

valve
  Reply With Quote
Old 13th January 2012, 08:35 PM   #3
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally Posted by VMUNIX View Post

I'm wondering what's the purpose of the cathodes connection to the S7 filament winding mid tap , is it for hum reduction ?
Also why is the filament winding for EZ40 connected to the +B and why is it using a separate winding S6 (I'm guessing it's the 5V for type 80, although the EZ40 has 6V filament).
Heaters are often biased positive with respect to the cathodes (of the input and phase splitter tubes) to reduce noise coupled from heater to cathode. Often it's done with a voltage divider from the B+, but the designer here saved a few parts by using the output tube cathode bias voltage, a clever idea.

Indirectly heated rectifiers usually have the cathode internally connected to the heater, so the heater is several hundred volts above ground- that's why it's run off a separate winding.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 13th January 2012, 08:48 PM   #4
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Valve, Sy, thanks you for your answers
what about the 10uH choke, I don't think I'll be using it, can I replace it with a 200ohm resistor? (perhaps using slightly bigger capacitors)
  Reply With Quote
Old 13th January 2012, 09:07 PM   #5
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
You mean 10H choke? Check the EZ40 data sheet before increasing C9.

EL41 has a reputation for overheating and becoming gassy, giving grid current and thermal runaway. However, if you have lots of them this will not be a problem.
  Reply With Quote
Old 13th January 2012, 09:29 PM   #6
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Quote:
Originally Posted by DF96 View Post
You mean 10H choke? Check the EZ40 data sheet before increasing C9.

EL41 has a reputation for overheating and becoming gassy, giving grid current and thermal runaway. However, if you have lots of them this will not be a problem.
I didn't know that, though I knew that the socket particularly had trouble with internal deposits eventually shorting the pins was replaced by the 9 pin socket.
bought these tubes for 50 cents

And yes you are right about C9, I'll make sure to stay below the maximum.

So what do you think all in all, can I go wrong with this for 10W ?
  Reply With Quote
Old 13th January 2012, 09:39 PM   #7
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
You might find that the input stage has too much gain and noise for modern sources. Try running in triode connection to reduce both.
  Reply With Quote
Old 13th January 2012, 09:56 PM   #8
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Quote:
Originally Posted by DF96 View Post
You might find that the input stage has too much gain and noise for modern sources. Try running in triode connection to reduce both.
Good idea, I will try that eventually.
One more thing , per your recommendation I checked the EZ40 sheet and found that it's rated at 350V each diode, and I have a 375 + 375 transformer, do you think it might hurt the tube ?
  Reply With Quote
Old 13th January 2012, 10:32 PM   #9
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
No, unless you stress it in other ways too. Rectifier limits tend to be a bit fuzzy, so you can break one to some extent provided you are nice to it in other ways. For example, a bit over voltage but less current or smaller caps than specified. Unless you really stress it, we are talking about lifetime not sudden failure.
  Reply With Quote
Old 13th January 2012, 10:37 PM   #10
VMUNIX is offline VMUNIX  Argentina
diyAudio Member
 
Join Date: Sep 2009
Quote:
Originally Posted by DF96 View Post
No, unless you stress it in other ways too. Rectifier limits tend to be a bit fuzzy, so you can break one to some extent provided you are nice to it in other ways. For example, a bit over voltage but less current or smaller caps than specified. Unless you really stress it, we are talking about lifetime not sudden failure.
Thanks you for your help, I appreciate it hopefully in my next thread I will post the project completed and my views about it, may help others who want to experiment with tubes other than the usual suspects.
  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 Supply Questions Uncle Paul Power Supplies 27 22nd May 2011 02:10 PM
PP power supply design questions Fat Daddy Tubes / Valves 31 27th December 2008 05:23 PM
questions about power supply for 6l6 pp dionisio Tubes / Valves 18 10th March 2005 02:14 PM
Question about PP EL34 power supply behaviour arnoldc Tubes / Valves 22 25th March 2004 04:39 PM
Power Supply Questions wrl Parts 7 29th December 2003 05:06 AM


New To Site? Need Help?

All times are GMT. The time now is 10:08 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