UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Closed Thread
 
Thread Tools
Old 5th Dec 2013, 11:48 am   #1
shiny phil
Retired Dormant Member
 
Join Date: Dec 2012
Location: Alicante, Spain.
Posts: 17
Question Mullard EF86 valve data sheet

I have been playing around with load lines, g1 bias points, effect of g2. Done some other reading re the g2 bypass cap and got very confused. The earthy end of the g2 cap can be connected to cathode or 0V. Gain reduction if not bypassed. Some where ultra linear was mentioned.
shiny phil is offline  
Old 5th Dec 2013, 11:55 am   #2
RF Burn
Hexode
 
RF Burn's Avatar
 
Join Date: Apr 2008
Location: Ramsgate, Kent, UK.
Posts: 252
Default Re: ef86 mullard valve data sheet

Not quite sure what you are asking but if you are looking for a data sheet on the EF86 that contains characteristic curves then one can be found here:

http://frank.pocnet.net/sheets/030/e/EF86.pdf

Adrian.
RF Burn is offline  
Old 5th Dec 2013, 12:00 pm   #3
G8HQP Dave
Rest in Peace
 
Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
Default Re: ef86 mullard valve data sheet

Some circuits using the EF86 (e.g. Mullard 5-10,5-20) inject negative feedback at the cathode. This means that the cathode is not grounded. It creates a choice about where g2 should be decoupled to: cathode or ground. For full pentode operation it should be cathode.
G8HQP Dave is offline  
Old 8th Dec 2013, 12:38 pm   #4
shiny phil
Retired Dormant Member
 
Join Date: Dec 2012
Location: Alicante, Spain.
Posts: 17
Default Re: ef86 mullard valve data sheet

I've seen a circuit can't remember where g2 bypass C was connected to cathode RC. Wondered why? The AC signal at g2 would flow through g2 C and cathode bypass C's. A easy place to connect earthy end of g2 bypass C.
shiny phil is offline  
Old 8th Dec 2013, 3:13 pm   #5
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: Mullard EF86 valve data sheet

I do not think you are correct. The valve varies its current which is taken from the cathode so the best place to bypass g2 is staight back to the cathode, making the loop as small as possible. There is then no part of the g2 current going through the cathode bypass capacitor or the chassis.
TrevorG3VLF is offline  
Old 8th Dec 2013, 3:44 pm   #6
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,798
Default Re: Mullard EF86 valve data sheet

The purpose of g2 is as a screen to spoil the Miller capacitance feedback path from anode to grid, allowing greater stage gain. In a pentode, this screening effect is shared by g2 and g3.

So we can expect the g2/g3 decoupling point to have to carry some current, which came capacitively from the anode.

This is easy if the valve is being used as a simple amplifier. The issue gets more interesting if the cathode is not completely decoupled, and more interesting still if the cathode is a point where a negative feedback signal is applied. We then need to start viewing the valve stage as having a differential input and a differential output. They won't be balanced, of course.

There isn't a single right answer to this issue. The decoupler should 'ground' to wherever the designer accounted for in his calculations.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now  
Old 21st Dec 2013, 2:53 pm   #7
shiny phil
Retired Dormant Member
 
Join Date: Dec 2012
Location: Alicante, Spain.
Posts: 17
Default Re: Mullard EF86 valve data sheet

Many thanks to all. Should have replied with thanks a wile ago. Life has been a bit difficult recently. I am grieving for the passing of a love one .

Next move do some reading. To get some sort of idea. Looked at 5-10 input stage as suggested. g2c to cathode, cathode R fully bypassed & NFB. know wonder I was confused thanks all
shiny phil is offline  
Old 22nd Dec 2013, 3:18 pm   #8
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,549
Default Re: Mullard EF86 valve data sheet

There is also a good data sheet here.

http://www.r-type.org/exhib/aai0113.htm
Refugee is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:33 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.