[Hallicrafters] Hallic. SX-24

[Roy Morgan]

At 01:43 PM 8/7/02 -0700, k7mks wrote:
>Am restoring a SX-24 and find that Vg to the 2 IF tubes (6sk7s) run -9
>to -20VDC instead of the usual slightly negative.  Vp & Vsg are OK.
>Removing the 6H6 DET/AVC has no effect on this high negative voltage which
>also appears on the RF amp. grid.  All caps have been changed. Tuning
>through an AM station it sounds like the BFO is ON  when it is not.


BINGO!!

Your IF is oscillating.

Check bypass caps, all ground points and especially whether the radio has a 
glass tube installed where a metal one with pin one grounded should be.

You have a feedback path you must find and cure.

   The
>source of the high negative voltage on AVC line has me puzzled.


Negative grid bias caused by an oscillation.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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