I've spent quite a bit of time trying to get the 5.7 - 10 MHz band to
come back to life on my Hammarlund HQ-129-X. I've got the user manual
which includes a schematic. When I got the receiver several months ago
I needed to "wiggle" the bandswitch knob to get this band to work. The
band then worked fine, especially my frequency of interest around 7.040
for cw. All the other bands worked without any "wiggling" of the
bandswitch knob.

Now after not being used for about 60 days no amount of "wiggling" will
get the 5.7 - 10 MHz band to come alive. It is as if the antenna is
disconnected. All the other bands work fine.

I've been taking a close look at S2 which is connected to the
bandswitch knob. S2 actually has six rotary switches, each with front
and rear contacts. I thought some spraying with contact cleaner, or
light swabbing with contact cleaner with q-tips would bring the band
back. I have had no success. All the other bands still work fine, but
not the 5.7 - 10 MHz band which is the one I want to use.

Any thoughts on what steps I could take next.

Thanks,

Bill Bird
Chesterfield, MO
www.billbird.com
kg0yj at arrl dot net

wrote in message
oups.com...
I've spent quite a bit of time trying to get the 5.7 - 10 MHz band to
come back to life on my Hammarlund HQ-129-X. I've got the user manual
which includes a schematic. When I got the receiver several months ago
I needed to "wiggle" the bandswitch knob to get this band to work. The
band then worked fine, especially my frequency of interest around 7.040
for cw. All the other bands worked without any "wiggling" of the
bandswitch knob.

Now after not being used for about 60 days no amount of "wiggling" will
get the 5.7 - 10 MHz band to come alive. It is as if the antenna is
disconnected. All the other bands work fine.

I've been taking a close look at S2 which is connected to the
bandswitch knob. S2 actually has six rotary switches, each with front
and rear contacts. I thought some spraying with contact cleaner, or
light swabbing with contact cleaner with q-tips would bring the band
back. I have had no success. All the other bands still work fine, but
not the 5.7 - 10 MHz band which is the one I want to use.

Any thoughts on what steps I could take next.

Thanks,

Bill Bird
Chesterfield, MO
www.billbird.com
kg0yj at arrl dot net


Try a good cleaner like Caig Pro gold or DeOxit. It may be a bad solder
joint too. Try touching up those connections with your soldering iron. I
some times use a nonconductive stick to lightly move the wafers and look for
intermittents, but don't damage the contacts, just lightly touch each one so
it contacts the moving conductor. Good luck


--
73 and good DXing.
Brian
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A lot of radios and 100' of rusty wire!
Zumbrota, Southern MN
Brian's Radio Universe
http://webpages.charter.net/brianhill/

EMAIL-
(Hide the $100 to reply!)

It is helpful to determine which stage is causing the problem. It will be
either the mixer, the oscillator or the rf amplifier. Some stages use 2
decks. See if you can hear the oscillator in another receiver. It is 455
kHz away from the tuned frequency, and you can hear it on a nearby receiver.

It could be a component so do not tear apart the bandswitch without
confirming that is really the problem. More than once I have spent time
servicing the wrong problem because I did not do a good job of diagnosis.

Fortunately, the penalty occasional incompetence is less than if the surgeon
removes the wrong part.

A signal generator can be used, too. Inject a signal (through a cap) into
the mixer, to replace a missing oscillator signal (remember 455 kHz away).
If no improvement, try injecting a signal into the mixer at the grid.

A little square wave oscillator with harmonics all over the place can give
you a quick diagnosis by putting it on the various grids of the mixer.

After enough projects like this, you will be answering questions, too.

Colin K7FM


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Thanks for the suggestions. I've definitely discovered something. The
5.7 - 10MHz band on the rcvr is pretty much fine from 7.35 to 10.0MHz.
I've been using my Heathkit SG-8 Signal Generator. Signal strength is
strong and calibration is good at 7.35MHz (bandspread set to high end,
#200 per manual). At the main tuning setting of 10.0MHz the frequency
is actually 9.940 (bandspread still at #200 per manual) and signal
strength is still strong. Both a modulated AM tone and the CW work
fine from 7.35 to 10MHz.

I purchased and used some DeoxIT but restrained myself from
disassembling the S2 switch assembly.

What I've discovered is that below 7.35MHz the signal strength drops
off DRAMATICALLY - so much so I had missed the signal from my generator
all together until I really listened. At 7.35MHz all is fine but by
the time I tune down to 7.30MHz reception has dropped WAY off. It
stays that way to the bottom of the 5.7 to 10MHz band.

Since the 40m ham band is in the area where my HQ-129-X is way down in
reception it is not usuable. I do believe that several months ago I
was able to receive well on the 40m band after "wiggling" the
bandswitch knob. That is a note I had written to myself for operating
hints. "Wiggling " doesn't do anything now.

Any additional ideas are welcome. I have not done all the tests
suggested but maybe this new information can help zero in on the
problem. I am going to be reading about the "realignment procedure" in
the manual for now.

Note: I am using my R1000 rcvr to determine what frequency my generator
is producing!

Thanks for any additional ideas and 73.

Bill Bird
Chesterfield, MO
KG0YJ
kg0yj at arrl dot net

I do believe that several months ago I
was able to receive well on the 40m band after "wiggling" the
bandswitch knob

For this I would use Brian's idea of the "magic stick"

I some times use a nonconductive stick to lightly move the wafers
and look for
intermittents

It has worked wonders locating intermittent problems on many of my
receivers.

Good luck,

Gil

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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"COLIN LAMB" wrote in message

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


LOL! I agree with everything you said Colin but this last part is the key.
You made my day. Thanks

B.H.