I finally got around to working on an HQ-160 I picked up a few years ago. It
works well, except the CW/SSB is very weak, and the slot (notch) filter doesn't
work at all.

I expect to check voltages around the 6U8 "linear detector" which I assume is a
product detector, though how it works is a mystery to me, being just a pentode
used as a triode. I know the BFO half of the tube is working, since I can hear
it change pitch with the pitch control on an AM signal.

The slot filter is strictly passive components. I've already played with the
slug in its coil, and the notch depth control. I just finished working with my
HQ-180, so I know how effective this slot filter circuit can be -- and my 160
just has nothing. I hope it isn't an open coil.

TIA for any suggestions -- Mike K. AA1UK

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In article ,
r (Mike Knudsen) writes:

I finally got around to working on an HQ-160 I picked up a few years ago. It
works well, except the CW/SSB is very weak, and the slot (notch) filter
doesn't work at all.

I expect to check voltages around the 6U8 "linear detector" which I assume is
a
product detector, though how it works is a mystery to me, being just a
pentode
used as a triode. I know the BFO half of the tube is working, since I can
hear
it change pitch with the pitch control on an AM signal.

I've worked on the PD circuit this AM, and it appears the primary of T8 (an IF
transofrmer used only to feed the PD) has a non-tunable primary. Since it
isn't open, I assume the internal shunt cap is shot.

For now I will just bypass the primary and feed the coupling cap (5 pF) from T7
to the secondary. That produces a CW/SSB audio level comparable to the AM
detector's. There will be nothing out the IF Output jack on the rear apron,
but I could move its pickoff to the secondary also.

What a shame the AVC doesn't work on SSB/CW. The circuitry is all there to
keep it on, but this being a transition-era rx, Hammarlund figured users would
want it off. The 170 and 180 got it right!

Haven't got to the slot filter yet. Dreading an open coil (like what else
could be wrong?) I've shot the Slot Depth pot full of DeOX-It, no help.

Again, thanks for any suggestions. 73, Mike K AA1UK


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Yet another question (sorry), about the HQ-160's slot filter circuit.
Given the schematic, should there be B+ up on the slot filter assembly on the
front panel, on the cable's center conductor? I have plenty of it there.

The schematic, no matter how cross-eyed I look at it, shows that every path B+
could take to the slot assembly is blocked by a cap. But I measure nearly 200V
on the cetner-tapped inductor under the chassis, the slot depth pot, and the
cable feed to the assembly.

I wonder if I have a shorted cap inside T3. However, both top and bottom slugs
of T3 are tunable. Maybe one of the .01 disk caps under the chassis is
shorted?

FWIW, the two caps on the assembly are keeping the B+ off the coil itself.
Also, shorting out the cable to ground thru a separate cap does not affect
anything.

Tnx, Mike K. AA1UK


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Make sure you have the IF's aligned per the manual as the selectivity,
sensitivity, and the slot depend on this. This is the same as with the
HQ170, 145, and 180 that use all or part of the HC-10 circuits.
Dave K4JRB

Mike Knudsen wrote in message
...
I finally got around to working on an HQ-160 I picked up a few years ago.
It
works well, except the CW/SSB is very weak, and the slot (notch) filter
doesn't
work at all.

I expect to check voltages around the 6U8 "linear detector" which I assume
is a
product detector, though how it works is a mystery to me, being just a
pentode
used as a triode. I know the BFO half of the tube is working, since I can
hear
it change pitch with the pitch control on an AM signal.

The slot filter is strictly passive components. I've already played with
the
slug in its coil, and the notch depth control. I just finished working
with my
HQ-180, so I know how effective this slot filter circuit can be -- and my
160
just has nothing. I hope it isn't an open coil.

TIA for any suggestions -- Mike K. AA1UK

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article k.net, "David L
Thompson" writes:

Make sure you have the IF's aligned per the manual as the selectivity,
sensitivity, and the slot depend on this. This is the same as with the
HQ170, 145, and 180 that use all or part of the HC-10 circuits.

OK, thanks. The IFs seemed to be well aligned, so I didn't check their freq
against a generator. The slot filter works on the 455 KC IF (the 160 doesn't
have the 3rd, loew 60 KC IF that the 170 and 180 do).

In fact, my 180's slot filter operates at 455 KC, not 60, which seems odd but
it works great.

Anyway, it's conceivable that my 160's IF is off, but it would have to be 10KC
or more off to be unreachable with the slot filter adjustment. But, next time
I have that radio off the shelf, I'll check the IF center freq. FWIW, the dial
calibrations line up *very* well -- I did touch up the front end alignment, and
the dial accuracies are worthy of a Hammarlund. Tnx es 73, Mike K.

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