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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 24th Jul 2020, 1:06 am   #1
falcon123
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Default Hallicrafters SX-42 IF alignment.

I'm stymied. I've rebuilt this set replacing most of the resistors and all the paper caps. I got lucky and I don't have any switch issues. I recapped the discriminator can. I've got sharp peaks in all the IF cans. the set plays very well on all bands after a preliminary RF alignment of the chassis out of the cabinet. The next thing to do was to adjust the crystal frequency IF. i'm using a Kenwood SG-5115 and a Fluke 79III. I've got Hallicrafters service data and Sams, and I'm getting nowhere fast. i do not understand the directions as to "rocking" the generator and adjusting S10,the bottom slug in the first IF. I assume rocking is varying the generator output a bit (How much?) and then returning to the set point of 455kHz while simultaneously adjusting S10 (how much which way?) and then looking for a decrease and an increase in output. As either adjustment seems to DROP output this all seems counter productive. It's impossible for me to understand WHAT I'm trying to change the setting of S10, the generator frequency, or both. I removed the crystal and it resonates at 451.6 kHz I was going to clean it but disassembly proved too risky as it appears to be welded together with varnish and solvents were impractical due to contamination. So back in it went as found. I even searched YouTube in hope someone would demonstrate this setting, but that came up nil, as well. I'd appreciate any constructive advice. I'm an not radio expert by any means.
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Old 24th Jul 2020, 9:10 am   #2
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Default Re: Hallicrafters SX-42 IF alignment.

Hello and welcome to the forums.

I recollect reading somewhere that the IF stages of an RCA AR88 should be aligned to the crystal frequency rather than the stated IF. The same may apply to your Halli. The difference between 451.6 kHz and 455 kHz does seem rather a lot though.
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Old 24th Jul 2020, 11:24 am   #3
falcon123
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Default Re: Hallicrafters SX-42 IF alignment.

thats an interesting observation since the sx-43 's alignment procedure calls for just that, in fact the sx 42 alignment says "with the signal gen.set at APPROX.455 adjust align slugs s-1,3,5....etc. and never goes back to those adjustments! i guess a 1947 signal generator would be an approximation at 455kc any way! the procedures for the two sets start off about the same but differs from then on. i can arrive at crystal peak by backing down the set on the generator where at 451.6 it resonates. (IVE no clue what s10 does in this scenario) i just dont understand how to adjust TWO settings at one time arrives at the intended result.and it gets worse as i go along
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