[R-390] 3tf7 replacement proceedure

[Dan Merz]

Norm,   Hi,  if I recall correctly,  I just put jumpers between these pins
(2 to 4 and 5 to 7) rather than moving the wires.  That way,  the 3tf7 could
still be plugged in without changes if you, or a later person,  wants to put
the 3tf7 in for some reason, or doesn't know you made the mod.  This puts ac
heater voltage on the two grids of the 12bh7 but that affects nothing since
you're just using the tube filament to drop the voltage  I have the socket
in my 390 hooked this way.  Now I'll have to check my notes to confirm that
I did this. ( added note: I just checked my set and that's the way I did it
- works ok for about 6 months so far)  Dan. 

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Norman J McSweyn
Sent: Monday, October 10, 2005 9:35 PM
To: r-390 at mailman.qth.net
Subject: [R-390] 3tf7 replacement proceedure

Hi all.
I've been doing some reading on the 3tf7 replacment schemes. For the time
being I think I'll use a 12bh7 in place of the 3tf7.
All I have to do is move the wire on pin two to pin four and the wire on pin
seven to pin five, right?
de n3ykf 


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