[Hallicrafters] Voltage question re SX-71

[Lee Bahr]

It's hard for me to believe the B+ is right on yet the other voltages are
off if considering the following.  When the transformers were wound, line
voltage was 110 volts.  Not today.  So, unless some method is used to lower
present day line voltages, how can 122 or 123 volts being pumped into a 110
volt transformer give ideal B+ voltage?  It won't do this.  Did you ever
consider checking the accuracy of your meter?  (One scale could be reading
low and one scale reading high.  What is your line voltage going into the
radio)?

I don't believe any of the voltages measured should be as the manual
specifies if 123 volts is being pumped into a 110 volt transformer.
Therefore I am skeptical of the validity of the data provided.
Lee, w0vt
----- 

> Yes, the B+ voltages are right on spec, so i think it is somewhere in the
> cathode bias/AGC circuitry, but am running out of things to replace :)
>
> The SX-71 has a fairly messy AGC/MGC/grid bias system, no two tubes using
> quite the same setup (unlike the NC183D in which all the RF and IF amps
use
> the same circuit) - a minor problem in grid bias voltages can affect the
> whole amplifier chain.
>
> Bob
>