In article ,
r (Mike Knudsen) writes:

Everything seems to work, except no modulation on SSB or AM -- that is, no
increase in RF out or DC in when I zap the mic center pin with a screwdriver,
with the AF gain turned full up

I got the audio and modulation working, and verified the rig works on SSB and
AM. The problem was a forehead-slapper: when I wnet to feed an audio
generator into the mic lead, I found a dead short to ground. Thinking the
shielded cable from the Amphenol connector to the audio tube had shorted out
(often happens when soldering melts the inner insulation), I lifted the cable's
ground at the tube end. Still shorted.

Then I got suspcious and checked out the mic connector more closely. Turns out
some genius at Amphenol had designed it so that when no mic is screwed onto it,
it shorts to ground! The center contact is on a metal plate that actually
moves in bit to flift the ground when you screw onthe mic cable.

So now I know I have a working HX-50. I'm tepmpted to (temporarily) rewire a
standard 3-terminal phone jack back there, to use my D-104 mic with PTT, and
wire the PTT screw terminal over to the jack. Then I could test the rig on the
air, maybe with the HQ-160 (don't want to risk the HQ-180 on the antenna relay
built into the HX-50 just yet).

Of course before selling the rig I'd put the Amphenol jack back in, right? Or
include it in the package and let the buyer decide?
73, Mike K. AA1UK

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In article ,
r (Mike Knudsen) writes:

Everything seems to work, except no modulation on SSB or AM -- that is, no
increase in RF out or DC in when I zap the mic center pin with a screwdriver,
with the AF gain turned full up

I got the audio and modulation working, and verified the rig works on SSB and
AM. The problem was a forehead-slapper: when I wnet to feed an audio
generator into the mic lead, I found a dead short to ground. Thinking the
shielded cable from the Amphenol connector to the audio tube had shorted out
(often happens when soldering melts the inner insulation), I lifted the cable's
ground at the tube end. Still shorted.

Then I got suspcious and checked out the mic connector more closely. Turns out
some genius at Amphenol had designed it so that when no mic is screwed onto it,
it shorts to ground! The center contact is on a metal plate that actually
moves in bit to flift the ground when you screw onthe mic cable.

So now I know I have a working HX-50. I'm tepmpted to (temporarily) rewire a
standard 3-terminal phone jack back there, to use my D-104 mic with PTT, and
wire the PTT screw terminal over to the jack. Then I could test the rig on the
air, maybe with the HQ-160 (don't want to risk the HQ-180 on the antenna relay
built into the HX-50 just yet).

Of course before selling the rig I'd put the Amphenol jack back in, right? Or
include it in the package and let the buyer decide?
73, Mike K. AA1UK

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

In article ,
r (Mike Knudsen) writes:

Everything seems to work, except no modulation on SSB or AM -- that is, no
increase in RF out or DC in when I zap the mic center pin with a screwdriver,
with the AF gain turned full up

I got the audio and modulation working, and verified the rig works on SSB and
AM. The problem was a forehead-slapper: when I wnet to feed an audio
generator into the mic lead, I found a dead short to ground. Thinking the
shielded cable from the Amphenol connector to the audio tube had shorted out
(often happens when soldering melts the inner insulation), I lifted the cable's
ground at the tube end. Still shorted.

Then I got suspcious and checked out the mic connector more closely. Turns out
some genius at Amphenol had designed it so that when no mic is screwed onto it,
it shorts to ground! The center contact is on a metal plate that actually
moves in bit to flift the ground when you screw onthe mic cable.

So now I know I have a working HX-50. I'm tepmpted to (temporarily) rewire a
standard 3-terminal phone jack back there, to use my D-104 mic with PTT, and
wire the PTT screw terminal over to the jack. Then I could test the rig on the
air, maybe with the HQ-160 (don't want to risk the HQ-180 on the antenna relay
built into the HX-50 just yet).

Of course before selling the rig I'd put the Amphenol jack back in, right? Or
include it in the package and let the buyer decide?
73, Mike K. AA1UK

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

Well, I found a nice mil/industrial 5R4WGB tube (with special plastic base that
covers up part of the tube), and also DLed the HX-50 manual from BAMA.

Very helpful to know the bias setting (50-60 mA) and how much cathode current
you dare load up (wow, 180 mA, that's a lot, given that a 6146 tops out at 150
-- however, the plate voltage allegedly drops to 600V).

Also that the little knob under hte PA on the relay compartment really is the
neutralizing cap. Beats reaching between the "hot" finals with a screwdriver,
like in those high-priced Iowa rigs.

Everything seems to work, except no modulation on SSB or AM -- that is, no
increase in RF out or DC in when I zap the mic center pin with a screwdriver,
with the AF gain turned full up. Hope that compactron isn't dead in one
section. Audio circuit should be easy to troubleshoot, especially since that
portion of the BAMA schematic is actually readable (there is a section with the
ghost of a tube just floating in space, with traces of wires and components
around it). If I need a better schematic copy, I'll ask.

Tnx for the discussion so far -- Mike K. AA1UK

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In article , - - Bill - -
writes:

had one many, many years ago and it was a good rig. I seemed to have
a persistent problem with popping diodes in the bias supply but that may
have been 'my' problem.

I think mine has the original bias supply diode. I measured the bias voltage
and it adjusts over a wide range.

I *did* find out that the other diodes in there were just replacements for the
low-voltage B+ supply, 375V or so. Four diodes in series-parallel. No idea
what the original was, other than Moore's book entry.

Will have to go up in my attic and break into the Rectifiers box to hunt up a
5R4. No wonder the wiring was intact around the socket. I guess the cathode
current I was reading was just screen current plus grid drive.

Mine had a regular Amphenol mic connector - dunno if that was original
but I didn't need PTT anyway :-)

Mine is what you'd probably call a single-pin Amphenol -- a big screw ring with
a hot contact in the center. I have some signal generator probes like that.
(The real problem is with my Ranger, whose Amphenol has two hot pins inside the
screw circule, one for PTT as you said).

With all the adjustments provided, the VOX inthe HX-50 should work well. It's
nice that it has a built-in antenna relay -- would be a nice match with my
HQ-160 or 180 (though I'd rather use the 180 for AM).

BTW, who designed that function switch -- you have to go thru the MOX (on)
postion to get from STDY to TUNE (CAL). Not the first nor last poorly laid out
rotary switch, but darn, this is a Hammarlund...

I wound up changing to 6146 just for the heck of it...no real difference.
It tunes up easy...assuming its neutralized just tune for max output.

Glad to hear that a 6146 drops in. I was thinking the 6DQ6 in there was a
seep tube, but the power trans' AC is over 800V and sweep tubes are usually
lower, IIRC.

But the 6146 pinouts and heater voltage will match OK?

I haven't cracked the PA cage yet (did Hammarlund own their own screw factory?)
but I trust there's a neatralizing cap in there.

What's the purpose of the nice air trimmer cap in the relay compartment below
the PA?

You really can't tune it up wrong. I recall it being persnikety about
the 6AW8 and 12BY7 (I think they were) having the tube shields firmly in
place - not unexpected.

Well I know I'm getting drive thru those -- turning up the Drive draws more
(screen) current in the PA. The shields are pretty rusty, but I have some
spares handy. Drive tuning is broadband per band, so assuming the coil slugs
are set right for each band, you are right, the tune-up should be easy.

Some rigs (like Viking II or KWM-2) are really paranoid about drawing too much
grid current, especially when tuning up without PA B+ applied. The HX-50
doesn't even have a grid current mode on the meter, so maybe this is less of a
concern?

Tnx and will keep you informed -- Mike K. AA1UK

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