[Hallicrafters] HT37 plate voltage

[Glen Zook]

Most of the older rigs run about 800 volts, or so,
with a pair of 6146 tubes under load.  You can use
either the 6146 or 6146A without any problems.  The
6146B is actually a different tube and may cause
problems if you substitute it for the original 6146. 
The only difference between the 6146 and the 6146A is
the make up of the heater ("filament").  The 6146B has
different interelectrode capacitances, etc.  You can
"mix" a 6146 with a 6146A, but NEVER mix a 6146B with
either a 6146 or 6146A.

If you try the 6146B tubes, make sure and neutralize
the final.  If the final will not neutralize, then
don't use the 6146B tubes.  If it does neutralize,
then check it for several days.  If the neutralization
"drifts", then go back to the 6146 / 6146A tubes.  If
the final does neutralize and holds the
neutralization, then the 6146B tubes will work fine in
that particular transmitter (individual transmitter,
the next one of the same model may not be able to use
the 6146B).

The problem with the 6146B is that they are very
"prone" to "taking off" (spurious emissions,
especially in the VHF range) when used in circuits
that were not designed originally for them.

You should be taking the voltage reading when in the
CW "key down" position so that the final amplifier
tubes are drawing the most current.  I think that 6K
ohm will be way too much.  You should have around 750
to 800 volts under load (144 watts input on CW if I
remember my HT-37 specifications).

Glen, K9STH


--- Randy & Jazz <ve7hrg at uniserve.com> wrote:

I had 850vdc on the plate choke in mox mode. A 6K 5
watt res. brought the voltage down to 750vdc(in the
mox mode). Is this the mode I should be taking the
voltage readings in?

Second Question;With all that voltage available ,
could 6146As be used?


__________________________________________________
Do You Yahoo!?
Yahoo! Sports - Coverage of the 2002 Olympic Games
http://sports.yahoo.com