[Hallicrafters] SX-100

[Kevin J Ward]

Wasn't the SX-100 one of those receivers with a "backward" meter
movement?  I seem to recall the needle on my friend's SX-100 going to
full scale when he turned the receiver off.  If so, the meter movement is
not necessarily bad.  This type of S-meter is basically a milliammeter in
the plate/cathode circuit of one of the IF stages.  A strong signal
generates AVC voltage, bias which reduces the plate current through the
IF stage, and the meter needle falls toward its resting place; in this
case, full scale.  

Substitute another tube in the stage which drives the S-meter and see if
needle action improves.  After that, check all the resistors and
capacitors in the meter circuit.  You can also check the meter with an
old style VOM.  Just make sure to set it to its highest range, and
briefly touch the meter terminals.  If you see a slight movement of the
S-meter you can switch the VOM to the next lower range and repeat.  This
should probably give you a one-third scale deflection.  If so, stop. 
Your S-meter is OK.  Look elsewhere for the fault.  

Good luck.

Kevin  N2IE

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