[Hallicrafters] SX28 2nd AVC.

[Brian Goldsmith]

Greetings to all.
The SX28 has two AVC systems,I have some problems with the second which is
centred around V5,6SL7 and V7,6B8.According to all of the various schematic
diagrams I have,grid(s) 1 of V5 and V7 are fed with an AVC voltage derived
from V7s detector diode(s).A glance at the schematic will show there should
be 100k of resistance between the top cap connectors of V5 and V7.In my set
there is an open circuit.I carefully sketched out all the existing
connections around the first IF transformer T1 and removed it from the
set.When I opened the transformer I was surprised to find a different setup
to that shown in all the schematics I have.When traced out,grid 1 of the
V7,6B8 has been removed from the 2nd AVC line and connected to the 6SA7
anode via a 270pF capacitor with a 500k resistor to ground from the grid.The
remainder of the transformer connections are as the schematics.The
transformer and associated wiring etc. appear to be completely original.The
mil manual calls up a type 50B082B 1st IF transformer,the transformer in my
set is marked 50 082B.Serial number of the set is H159134.
Can anyone shed any light on this difference and why it should be so?

Brian G.