Reduction & Fine tunning of Test Level voltages Huntron 1005b-S1, below turn On

[cog7997]

hi,

re: Huntron Tracker 1005b-S1
  S/N: 214o3150

How to modify a Huntron 1005b for lower Low-Range Test-Voltage Levels ?

I need lower Test Signal Voltage levels than the Original 10V { 7Vrms } Huntron 1005 Low Range:
to view other passive components in-circuit and to examine Semiconductor Turn On effects from the lower limits, upwards. Also to examine different Semiconductors that have lower Turn On voltages:

The experimental interests are  6V, 5V, 3V and 1.5, 1.3V, 0.6V 0.3V & 0.2V

For in-circuit PCB testing of older 1950's to 1960's transistors where I do not want to damage the transistors in Reverse Bias testing (B-E, etc.) and want to avoid modifying the  hfe of  these older fragile Fabrication process Si & Ge by using a 10V { 7Vrms  is too much ! } voltage level during testing and repairs.
A great number of these old transistors have no modern equivalents for their circuits, one needs to be extremely careful.

For other semiconductor devices, having Turn-On voltages of less than 3V, having multiple materials, Schottky diodes, etc.

-- How to modify the 1005b-S1 ?
How low can the 10k Pot, R11 go,
Or, in different schematics perhaps R6,R7, R8  ?

  so that I can obtain lower Signal Output Voltage Levels,
    than the "Low" range provides.

i.e. Use some switches that will provide several Lower Ranges ( when in the Low Range ) with fixed resistors and pots switching the Normal R11 out of the circuit ?

In one Maintenance manual Section 4.3 & 4.4 ,  R11 is used to adjust the Signal Level.
... what the limits are for R11 ?

Or use a Transformer on the O/P leads of the Huntron
 ( see below YouTube video from India, done on a Huntron 2000 ) ?


https://www.huntron.com/privatesales/technical/1000-21a-maint-info.pdf
  { not sure if this Manual applies directly to my 1005b- S1 Serial Number. }

&

Huntron 2000 to 2800 
Test O/P  Voltage Level signal reduction modification, via transformer:
https://www.youtube.com/watch?v=WFDsjMJu6cU

Damage to Transistors by Voltage Levels higher than 6V ( B-E reverse bias issues damaging hfe, etc. )

https://audiokarma.org/forums/index.php?threads/huntron-tracker-1000-and-transistor-damage.1032911/

https://huntron.com/sales-support/pdf/independent-study.pdf

thank you
**