Hi Bill:

This is where radio diagnosis becomes as good as an old Sherlock Holmes
mystery - even better because only you will write the conclusion.

Using logic (sometimes the weak link of radio repair), it is not likely (but
possible) that that the bandswitch works at the high end and fails at the
low end.

However, I must say that many of the broken receivers that end up on my desk
have been realigned to the point that that has become their problem.
Realignment of something like the HQ-129X is pretty basic and easy to do
with a calibrated signal generator, but sometimes that may not be the
problem.

Aging is not likely to change realignment substantially, rather it is
incremental. So, the cause is likely to be something else.

The oscillator stage is working and injecting a signal into the mixer - but
the level could be decreasing as you get lower in frequency. Use your R1000
as a signal level measurement system and determine whether the signal leve
at the mixer grid is less at the low end than the high end. Likewise, use a
probe (small wire loop at end of small coax cable near the point to be
tested) on your R1000 to determine whether the signal level through the
front end and mixer input tuning changes with frequency (using SG-8). If
so, then try rf stage alone.

An ineffective bypass cap on the downhill side of the tuned circuit or one
on the input downhill side can cause the coil to be ineffective - more at
the lower frequency end, so look there. Maybe there is something switched
in on that circuit only.

You can also check each tuned circuit before aligning by clipping on a 10 pf
or so cap to the open connection on the top of the variable to ground. If
the signal decreases, increased capacitance or inductance at the frequency
will not help. Likewise, you can use a brass slug attached to a wand and
insert into appropriate coil to see if less inductance or capacitance will
help at that frequency. If both decrease signals, then realignment is not
needed.

Finally, if nothing works, go out and have a cheap beer wait until tomorrow.
After enough of this, you will wake up in the middle of the night and know
what the answer is.

After years of doing this (and being successful), you can write adetective
book on radio mystery solutions and sell both copies on eBay for $15.

73, Colin K7FM


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