[Hallicrafters] SX-16 RF gain circuit question

[rrkrr]

Mike,
Are you sure that's the wiper?  Many old radios had an extra fixed tap 
on the volume control pot at about 1/2 way around with a series RC was 
connected from it to ground.  The time constant on the RC was such that 
high and mid frequency ranges were attenuated for volume settings near 
and below the tap, so that the bass was emphasized.  This was for a 
"bass boost" at low volume
to compensate for the rolloff in human ear sensitivity to bass tones at 
low volume.

Bob K4ERR

Mike Everette wrote:

> My SX-16 seems to have a number of differences from the published schematics I've found.  One is in the RF gain control circuit.  Can someone take a look at their receiver and advise whether this is correct?
>
> My receiver has a 100 ohm resistor from the RF gain control wiper, to ground.  The resistor looks original; but the diagram shows the wiper going straight to ground.  There's an 0.002 uf cap caross this resistor.  This cap is a modern, recent replacement.  The schematic doesn't indicate such a cap.
>
> I acquired this receiver "recapped" but several capacitor values were found not to be correct (not to mention a few wiring errors).  If the RF gain control does have a resistor and cap to ground, is 0.002 uf correct?  Is this cap grounded by soldering the cold end to the chassis?  Whoever recapped it grounded the cap to a lug that grounds to the busing on the RF gain control; I doubt this makes much difference -- or is there an obscure reason why it might?
>
> Also, capacitor C-46 in the audio section -- if I remember right without the schematic in front of me, this is the decoupling cap for the B plus side of the AF driver transformer primary -- is this a 1 uf electrolytic, as shown in the parts list, or is it actually 10 uf?  This cap mounts in a clip under the chassis, at the rear near the AF output tubes.  I rather suspect it's a 10 uf, judging by the photo of the pictorial parts layout, because the cap is physically huge; but can someone confirm this?
>
> Thanks and 73
>
> Mike
> WA4DLF
>
>
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