[Milsurplus] Fixing up an I-177B tube tester

[Ian Wilson]

I would have thought this was easy enough that I could figure it out; but I
could
use some help here.

Problem #1: can't adjust line to correct meter position
  It reads low. If I crank it up to max the meter reads in the white zone
just below
  the correct line position. However, this gives excessive filament
voltages. I have
  measured all the resistors I can get to easily (especially the meter shunt
and
  series resistors when in LINE mode), and have checked both rectifier
  tubes. Unless the meter sensitivity has changed over time, I'm stumped.

Problem #2: no reading on AMPL
  Nothing happening with a working tube. I can see the filaments are heating
OK.
  Removing the tube and looking at the voltages between plate and cathode
(pins
  5 and 8 for my test tube, a 12SK7) shows nothing (AC or DC) with or
without
  AMPL pressed.

The rectifiers are both lit. I measure 127V to ground on the 83 filament and
130V
to ground from the 5Y3GT filament.

Suggestions welcomed.

74, ian K3IMW