[Hallicrafters] SX101A Problem

[Mark Shaum]

Unfortunately, it does sound like your problem is internal to T5.  I'd
bet one of its leads to the top coils has broken off.  The work-around
is to stay in LSB and use the BFO as needed for reception until you have
time to remove it.  I've had more luck than expected repairing the
insides of RF and IF coils, leads usually break at the terminals on the
bottom or right at the coil winding, where there is usually a tiny stub
of wire left that can be scraped with a razor blade and tack-soldered
to.  Broken slugs can be epoxied back together as well.

Replacing the black beauties is strongly recommended either way.

Good luck!  The 101A is a fine old receiver.  I have a 101A and an older
101 mk 2 that I use for weekend 160 meter AM nets.

Mark K9TR

----- Original Message -----
From: "Franklin Baker" <franklinbaker at mchsi.com>
> Mark:
> I will check P2 of V5 and see what I get.
> Below is more info on what I have done:
> I used a freg. Counter to set the Signal Generator.
> I have the receiver in receive mode. I made sure the TX/RX issue was
not in
> play here.
> I'm getting no readings on my VTVM while connected to the speaker
terminals
> 1 volt scale. While the Signal generator is connected to Pin 7 of V2
> I'm getting .35 VDC on test point B detector voltage. No changes when
I
> change Sig. Generator's freg. or adjust T5 top slug.
> I pulled the unit out of the case  because I was getting AC feedback
into
> the receiver. I was intending to swap out the black beauties in this
old
> girl.
> I hope I don't have to replace T5 it looks like a hard job.
>
> ----- Original Message -----
> From: "Mark Shaum" <k9tr at dtnspeed.net>
> > T5 contains the plate tuned circuits for both of the sections of
V12.
> > Either the top or bottom tuned circuit is in use depending on which
> > sideband is selected.
> >
> > I'd guess a connection within T5 has broken internally, or perhaps
one
> > slug is fractured.  You can try adjusting the slugs per manual to
see if
> > you can regain oscillation.  If this doesn't work, it will likely be
> > necessary to remove T5, disassemble it and fix whatever needs fixing
> > inside.
> >
> > Check with a scope or RF voltmeter at pin 2 of T5, there should be
> > roughly equal output level as you change the mode switch from USB to
> > LSB, but of course the frequency will shift between 1600 and 1700
khz.
> > A convenient spot to check this level would be pin 2 of V5 as the
> > undersides of the little subchassis are not reachable easily without
> > removal.
> >
> > Mark