[Heathkit] Re: GB> Fixed: was: HW-16 audio troubles

[Tom NØJMY - AAR7FV]

Thanks, Bob and Larry.  Well, the roll-off starts to dip down into the 
area under about 1500 Hz. if I go bigger than .01 uf.  Being this is a 
CW only machine that isn't a problem.  In fact, that little 2-pole IF 
filter might have been advertised as 500 Hz. wide, but the shape factor 
makes the response curve look like a circus tent.  We should be so lucky 
as to have a little more roll-off, both high and low!  That's why I 
usually install a CWF-2 at the detector.

HOWEVER...I agree with Larry that this screen-grid bypass mod is 
probably just wiping out the effects of a problem further up stream, 
which is what I was meaning by a "brute strength" approach.  It bugs me 
a little and I'm kind of a glowbug puzzle fiend.  I enjoy searching for 
the answer.

Here is a nice legible schematic of that section of the rig if anyone 
cares to search along with me:

http://www.theponyengine.com/HW16aud.gif

So far it has eluded me.  The hum does not appear to be present at the 
grid of the st audio (the other half of the same 6HF8.  Perfunctorily 
bypassing the other terminals of the tube socket has had no effect. 
Voltages at that socket are in spec. except for the grid of the 1st amp 
(is -.42, should be -.8) and the B+ of the same half (is +67, should be 
+78).

Always appreciate a good HW-16 discussion,
Tom.... who was sired by H.W. Farland