[Hallicrafters] SX-42 Phone Jack

[Roy Morgan]

At 06:42 PM 9/12/2007, HallicrafterSX28 at aol.com wrote:
>Hi
>If you look at the schematic ,the headphones are driven by the   voltage
>amplifier 6SL7 tube ,not by the final power stage.

The SX-88 works the same way. The headphone jack disconnects the the input 
to the 6V6 audio output stage and grounds it as it connects the audio 
driver to the phones.  This is a very handy way to hook up an external 
amplifier, though it's not needed in these radios since the radio itself 
has a very fine P-P 6V6 amp in it.

Check the operation of the contacts in the phone jack. Clean with stiff 
paper or business card with a drop of De-Oxit on it.  It looks to me  from 
the Sams page I have here that the jack is one of those right-angle jobs 
and is quite accessible from the bottom of the radio.

While you are at it, if the coupling caps in the audio stage are original, 
change them now - (C106 0.01 and C109 and C112 both 0.02).

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-975-6097
roy.morgan at nist.gov --