My perspective is somewhat odd ¨C every boat anchor I restore is a learning experience.? I tend to fuss around with things not because I¡¯m unsatisfied, but because I¡¯m curious. ? On the crystal ¨C after much more research, the crystal is loose in the chamber inside the holder because that¡¯s the way it was.? I also discovered that the IN-circuit resonant frequency is going to be somewhat different than the OUT-of-circuit resonance; therefore, there¡¯s no significant value in testing the crystal outside of the radio unless a bad crystal is suspected.? And, as you¡¯ve pointed out, the potential difference in resonant frequency from repositioning the radio is rather minimal.? I¡¯m still going to test with a replacement 455 KHz crystal anyway ¨C because, well, I¡¯m curious. ? Next I have a question about the IF alignment, but will post that under a different subject so this doesn¡¯t go on forever. ? 73 ¨C Steve, KW4H ? ? ??Is it just me (always a possibility!) or have we lost some perspective here? ? If you're getting +/- 50 hertz out of a 61 year old single crystal filter in a $160 radio made when Eisenhower might have been President, just align the radio at 453.750 and you'll be fine. Like you, I >am< a little circumspect about anything rattling around loose in the crystal case when shaking it. That's curious. I've removed, handled, and measured several crystal cases like yours from the single conversion HQ Hammarlunds and they don't rattle. What inside the case assembly makes you think the crystal was intended to be mounted loosely when you took it apart? Maybe it should be? I've never opened such a case. Could be, I guess. But a loose mounted crystal wafer rattling about and being OK isn't an intuitive conclusion. Like to learn more about that. Please continue posting since this is of interest to us. I'm especially curious how you intend to remount the new 455 crystal you have coming. Summarizing, I'm suspicious of the rattling sound you report when shaking your crystal case - seems a red flag to me - but +/- 50 hertz?? You'll never hear it or know it. Align it at 453.750 and go shortwave listening!
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On Nov 2, 2022, at 5:01 PM, KW4H via groups.io <reedsteve@...> wrote:
? The crystal from the SX-71 did the same thing in the test setup, with the signal generator and scope.? For now, I¡¯ve returned the original crystal to the SX-110 and am going through the IF alignment again, but this time with more knowledge about the resonant frequency.? Want to see where I land and more about the effects of repositioning the radio (on its side, right side up, etc).? The new(er) 455 KHz crystal will be here in a few days ¨C I¡¯ll swap it out then and we¡¯ll see what effect that has, following another alignment. ? 73 ¨C Steve, KW4H ? Steve ¡ doing the same thing in the test setup or in the receiver or both? I am a curious reader at this time Don VA3DRL ? ? Yeah, I ordered a couple of 455 KHz crystals today.? It would be good to have another on hand.? ? FYI, I stumble onto these things because I restore boat anchors (mostly receivers) for educational and historical purposes.? I also write articles for ER magazine, and the extra information is fun and interesting.? Anyway, I¡¯m more likely to remove a component and test it out of curiosity rather than questioning the design.? The unstable crystal caught me by surprise! ?And just for the heck of it, I pulled a similar crystal out of a SX-71 awaiting restoration and it¡¯s doing exactly the same thing.? Still mulling that over. ? 73 ¨C Steve, KW4H ? I've owned several SX-110's over the years, including the one I used as a Novice back in '67, that was like new I acquired from original owner. Never had any issues with xtal instability. They all were fairly stable after initial 10-15 min. warmup. Sounds like you need a new xtal.
In a message dated 11/2/2022 1:23:14 PM Eastern Standard Time, reedsteve@... writes:
Sent from Proton Mail for iOS On Wed, Nov 2, 2022 at 10:20 AM, Richard Knoppow <1oldlens1@...> wrote: I am not an expert but think this is not normal.? ?It looks like the crystal holder comes apart.? ?Perhaps cleaning crystal and electrodes will fix it. -------- Original message -------- From: "KW4H via groups.io" <reedsteve@...> Date: 11/2/22 9:28 AM (GMT-08:00) Subject: [HallicraftersRadios] SX-110 Crystal Instability Attached is a photo of the crystal in my SX-110.? I pulled the crystal to test its resonant frequency using a sig gen and scope, and the darn thing is so unstable it¡¯s driving me loopy.? The resonant frequency can vary (roughly) between 453.700 KHz and 453.800 KHz by simply moving it around, no matter how gently.? Pardon my ignorance, but is that normal for crystals of this vintage?? Is there a reason, operationally in the Hallicrafters, for a crystal to act like this?? Before I order a different (and more stable) crystal to solder into the circuit, thought I should ask. ? 73 ¨C Steve, KW4H ? ?
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