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From: rdm1@midway.uchicago.edu (Mast  C.D.M.)
Subject: Dyna ST-70 Triode Mod.
Date: Tue, 8 Jun 1993 19:46:46 GMT

I've gotten numerous requests for instructions to convert EL-34's from pentode
to triode operation.  I think there should be a group dedicated to Dynaco, but
for now the high-enders can put up with us.  (I'll leave the debate of whether
this is high end or not to others.)

Disconnect the wire that goes from the transformer to the screen tap (pin 4).
Insulate the wire and forget about it.  Short pins 3 and 4 together.  (Pin 3
is the 'plate' if I recall correctly.)

That's all.  Amazingly simple.  I noticed a fantastic improvement in sound,
without a noticable power loss.  

Try it.  It's easy enough to undo if you don't like it.  But you will.

-Russell
MASTRD@ctrvax.Vanderbilt.edu

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From: rons@tv.tv.tek.com (Ron Selberg)
Subject: Re: Dyna ST-70 Triode Mod.
Date: Wed, 9 Jun 1993 15:49:58 GMT

When converting from pentode to triode mode it is best to connect the
screen to the plate through a 100ohm non-inductive resistor. In other words
not a wirewound one. 1 watt resistor BTW.
Ron
 

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Subject: Re: Dyna ST-70 Triode Mod.
Date: Wed, 9 Jun 1993 17:33:51 GMT
From: !balon@cup.hp.com

In article <1v4lqnINNsln@uwm.edu> rdm1@midway.uchicago.edu (Mast  C.D.M.) writes:
>Disconnect the wire that goes from the transformer to the screen tap (pin 4).
>Insulate the wire and forget about it.  Short pins 3 and 4 together.  (Pin 3
>is the 'plate' if I recall correctly.)
>

	I've seen a similar write up in Glass Audio. However, instead of
	just connecting pins 3 and 4 ( plate and screen ) directly, they
	suggest inserting a 100 ohm resistor between the pins. The reason
	given was that since the screen grid (g2) has a maximum dissipation 
	of around 8 watts, the insertion of the 100 ohm resistor makes 
	the plate take the majority of the current flow. (the plate is rated
	for around 25 watts) 

	Regards,
	Tom