[Heathkit] Question on 12AU7

[Yong Surk Lee/HL1FB]

It is not a good idea to replace the 12AU7 in Heathkit SB-100
with a 5814. In the SB100 circuit, the 12AU7 filament is paralleled to make it
a 6.3V 0.3A filament. And it is series connected with another 6.3V 0.3A tube and 
12.6V is appled from HP23.
So the 12AU7  filament will see 6.3V applied to its paralleled filament, however,
if 5814 is used instead of 12AU7, the 5814 will see only 5V at its filament when 12.6V
is applied from the HP23 power supply. This can cause poor performance of the radio.
So do not replace 12AU7 with 5814 in Heathkit SB-10* series.
 
--- Original Message ---
From    : "Dan Pividal"<dpividal at tampabay.rr.com>
To      : "heathkit at mailman.qth.nt"<heathkit at mailman.qth.net>
Date    : 2008/02/02 토요일 오전 1:50:31
Subject : [Heathkit] Question on 12AU7

Is the 5814A a direct substitute for a 12AU7A?
I show it is when I go to some tube sub charts.
I have a bunch of 5814A and would like to know.
Dan/N4VET