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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 27th Aug 2020, 4:41 am   #161
mrrstrat
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Default Re: Another Hallicrafters Sky Champion S20.

Ok things are happening now with the set: localizing the issue I found that the way it was wired when I got it - and I assumed it to be original - was not capable of working. It did not match the Hallicrafters schematic nor looked like a normal variation of the circuit (typical variation of handmade sets). I removed the extra caps and replaced the IF can with a NOS one I have. I have seen this over use of caps not on a schematic before: I have a set from the estate of a radio guy who fixed and repaired radios and he used 0.01uf caps everywhere like how a chef uses salt and pepper. I guess he just dropped them everywhere until things got quiet (and affected the functioning of the set in the process).

After doing that and correcting the way it was wired (and a few other deviations) the set came alive! It was incredibly loud. And better yet the injection of a modulated signal at the 6L7 resulted in a nice rich tone to use to get the IFs all set up. The set took a nice alignment and works on all bands.

The only gripe I have is that the medium wave seems to not have the selectivity it should (some additional stations seem to be combined together making an occasional cacophony station on places on the dial. The other bands do not bleed together.
What might cause this on medium wave band?

The only other gripe is that the BFO is not as strong as I would like and I did not see a procedure to align the BFO transformer can. It seemed to work great through the signal tracer but not so much though the set is very loud and rich in sound and dials stations in everywhere.

Maybe I am not done yet..
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Old 27th Aug 2020, 11:17 am   #162
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Default Re: Another Hallicrafters Sky Champion S20.

Good to know it's working at last.

Sounds like you're picking up image signals on MW. Full realignment should cure this.

BFO injection level can be adjusted by adding more twists to the "gimmick" capacitor C31.

Procedure for "aligning the BFO is to set the pitch control C33 at half mesh at which position any dot or mark on the knob should line up with the mark on the case. Then adjust the trimmer across L1 for zero beat with a received AM signal. You should then hear the beat note rise in frequency as you move the knob either side of the zero beat position.
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Old 27th Aug 2020, 1:07 pm   #163
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Default Re: Another Hallicrafters Sky Champion S20.

Another (silly perhaps) question: Is it OK to move the wires in an IF to be closer to where they need to go in the set even if it means crossing them?

When I popped in my new IF I moved two of the wires along the same side of the can to be closer to where they needed to go. I did not think anything of it until my medium wave (local AM stations) appear to wanna bleed together. I did not think this was an issue as when I took of the IF it replaced the wires internally were crossed. I am sure I am the only one who ever took it off this set as the screws were factory red paint dot set and had the "never been off before in 50 or more years" look.

I did "OK" with my alignment on this set. I spent 4 hours on my SX-43 tweaking and tuning it. This one was only the third set I ever aligned and I thought it sounded like the stations were too close together (as if the band padder needed an adjustment to 'stretch' the working range out). But the RF gain is pretty sensitive and I am getting to know this set still. It may be I am overloading the signal and the alignment is sub-par.

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Originally Posted by Station X View Post
Good to know it's working at last.

Sounds like you're picking up image signals on MW. Full realignment should cure this.

BFO injection level can be adjusted by adding more twists to the "gimmick" capacitor C31.

Procedure for "aligning the BFO is to set the pitch control C33 at half mesh at which position any dot or mark on the knob should line up with the mark on the case. Then adjust the trimmer across L1 for zero beat with a received AM signal. You should then hear the beat note rise in frequency as you move the knob either side of the zero beat position.
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Old 27th Aug 2020, 1:12 pm   #164
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Default Re: Another Hallicrafters Sky Champion S20.

Come to think of it before my last set of changes I was able to pickup some stations twice within a short dial twist of the dial. I knew them to be image signals and when I corrected the ground of the second IF to exactly match the schematic the entire set opened up and became a radio again.

Quote:
Originally Posted by Station X View Post
Good to know it's working at last.

Sounds like you're picking up image signals on MW. Full realignment should cure this.

BFO injection level can be adjusted by adding more twists to the "gimmick" capacitor C31.

Procedure for "aligning the BFO is to set the pitch control C33 at half mesh at which position any dot or mark on the knob should line up with the mark on the case. Then adjust the trimmer across L1 for zero beat with a received AM signal. You should then hear the beat note rise in frequency as you move the knob either side of the zero beat position.
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Old 27th Aug 2020, 1:15 pm   #165
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Default Re: Another Hallicrafters Sky Champion S20.

Big thanks for the help on this from you and the forum members!

This set would not have been able to be fixed without the help of the people who jumped in on this thread (and of course your continued help). I hope this who thread helps someone down the road in getting their set going

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Good to know it's working at last.
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Old 27th Aug 2020, 9:13 pm   #166
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Default Re: Another Hallicrafters Sky Champion S20.

The set now:

- Checked all tubes, picked the best of the best with a TV-7 and made sure they worked w/o noise
- Tested and checked all lead dress inside - checked wire proximities and crosstalk potential (all clear)
- Has a good alignment (was able to execute the entire process to the documentation)
- BFO works (and on the correct tube - I used my S20R as an example of what the BFO gimmic twist should look like)
- PT made a humming noise earlier today - I have encountered this before and just torqued the bolts on it to tighten the PT element laminations (now its quiet as it should be)
- Now giving it the 'three hours on' test and tonight will be the SW reception test

And now for the first time in months I can entertain putting the cover back on and putting on the shelf next to the others!
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