Recently purchased an SX-122 in great condition.? ?Less cosmetic wear than you'd expect from an early '60s radio.? No mods or changes underneath and very clean there as well.? A few tubes had been changed but several still had the Hallicrafters markings.? Five of the tubes tested below acceptable level on my calibrated Hickok 539, so replaced them with NOS tubes that tested to spec.? The set performed well on my very short length wire that starts on the workbench in the basement and makes it's way up to the roof on the deck.
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With that done, I replaced the two discrete electrolytics, which showed increases in both capacitance and leakage. and ordered a replacement can cap.? Although the set is playing without any power supply hum, I change all 50+ year old electrolytics on general principles.? I located the five paper caps and found them to be high quality, not waxies, and looking as if they just came out of the box.? All five tested on my LCR meter to their nominal capacitance and the leakage was very small and virtually the same as the ones I would have replaced them with.? So, left them in.
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While waiting for the can cap, I decided to give it a preliminary alignment to see how far out it might be.? Tuning up the 50Khz made a big difference.? Had an issue getting an output on the 1,650Hhz IF.? Triple checked my setup, non-inductive 4 ohm dummy load on the audio output with the VTVM measuring across that, and still not seeing what I expected on the VTVM.? Even weirder with the speaker connected.? But, as I said, the set is working the second IF must be too.? Put that on the back burner waiting on some expert guidance and went ahead to the RF alignment.
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Starting with 30 & 14Mhz.? Pretty straightforward and was doing fine.? Got significant improvements at 30Mhz and was feeling good until I got to 14Mhz.? L12, L8, and L4.? Well L12 was no problem as it's threaded section comes an inch or two out of the top of the coil and uses a straight blade screwdriver adjustment (I use on ceramic screwdrivers wherever possible).? Man, that thing twitchy but finally conquered it and got significant improvement.? However things ground to a screeching halt with I hit L8, and L4.? The slugs are recessed and the opening on top has a lot of wax on it.? Doesn't block the hole, but it's darn hard to see down in there and figure out what shape tool is required.? I'm being very cautious about not damaging a slug.? One that I can see reasonably well apprears to have a wide, shallow, common screwdriver slot.? Wasn't able to get anything in that felt like it seated and no changes in output.
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So, to wrap up, I'd appreciate any thoughts on the 1,650 Khz alignment.? And also some guidance on what's needed to turn the slugs on all the recessed slugs.
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Thanks,
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John - K8NN?
