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Pentode/Triode switch


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4/22/2002 4:53 PM
Steve Jones
 Pentode/Triode switch
Has anyone added a pentode/triode switch to their 5E3 and what were the results?  
 
In adding the switch, the stock 5E3 circuit does not have screen grid resistors. All the pentode/triode switch circuits I've seen have a 1K5 screen grid resistor. Is that resistor necessary, or can I leave it off?  
 
Thanks,  
 
Steve Jones
  
4/23/2002 12:25 PM
ChrisW
It's good/safe to use a 470 - 1500 ohms R between g2 and the plate in the triode-mode .  
 
You can connect the Rs to the plates and switch the screengrids between those , added Rs and the 5k R .  
 
Have fun !  
 
Chris
  
5/10/2002 9:05 PM
Steve Jones
Hi Chris,  
 
Thanks for the reply. Sorry not to reply back but for some reason did not get the email saying you had replied to mine. Maybe I didn't check the little box...  
 
Are you saying just to use the screen grid resistor when in Triode mode? Does it hurt to use in both?  
 
Thanks,  
 
Steve
  
4/27/2002 5:23 PM
frankenstein
Steve: Can you refer me to a drawing for this mod. I can't really follow what Chris replied.  
/ frankenstein
  
4/29/2002 9:06 PM
risW
Hi Frankenstein !  
 
I truly wish my english was a bit better . I'll try to make a drawing for you and I'll look for some regular penthode/triode-switching-diagrams for you .  
 
:)  
 
Chris
  
5/2/2002 11:20 PM
frankenstein
EXCELLENT ! Post it here as I bet a lot of the guys would like to see what it's about and try it.  
/ frankenstein
  
5/10/2002 9:01 PM
Steve Jones
Sorry about not replying. I never got the email saying that someone had replied to my post so didn't know you had posted the question and it's been awhile since I've visited (I thought no one had answered my question).  
 
For a schematic of this there are a couple sources. Lord Valve has a schematic that is on Steve Ahola's site.  
 
Also, on the AX84 site, if you go to projects and select AX84 P1 there's a theory document (.PDF file) that towards the end shows how to do it.  
 
If you need URLs for those sites let me know.  
 
Steve
  

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