[Hallicrafters] HT-37 Bias

[wb8jkr at juno.com]

 Finally got a chance to actually look at the schematic,
 Looks like the operating bias (xmit) is -49 volts or so,
and the cutoff bias is created by relay contacts J and K
opening during receive periods. I didn't sit down and
do the math, but my guess would be that the bias goes 
to around -70 or so when the operation switch is in
any position other than the "MOX" position. 
 
Mark  WB8JKR


> On Thu, 19 Aug 2004 14:16:44 -0400 k2wh at optonline.net writes:
> > I plan on checking the bias voltage at the test point AGAIN, but I 
> 
> > know it is -49vdc.  I have check this numerous times and it is 
> > always within a volt of -49vdc.  However, looking at the 37 
> > schematic, I noticed resistor R19, 1000 ohms in series with both 
> > grids.  It is possible this resistor is no longer 1K but has moved 
> 
> > higher thereby increasing voltage drop across it and forcing the 
> -49 
> > at the tube socket to some other low value.
> > 
> > Anyway, I plan on checking the bias voltage at the supply test 
> > point, check R19, check bias voltage at the tube socket and also 
> > lift the plate voltage lead and measure the idling current.  These 
> 
> > measurements should once and for all establish what is going on 
> here 
> > if anything.  My instincts lead me to R19 as either bad or changed 
> 
> > in value or, nothing is wrong at all and the rig is operating 
> > normally.
> > 
> > K2WH


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