Hallicrafters SX-110

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Re: Hallicrafters SX-110

Post: # 11985Post TC Chris »

So that crystal is a switchable filter after the converter. Sharp, narrow, crystal, normal. Figure out exactly which frequency the crystal peaks at, and use that to align the IF, and then do everything else as usual.

My best guess.

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Re: Hallicrafters SX-110

Post: # 12003Post electra225 »

Thank you, Doc, for the link. I watch that guy's videos on flat panel TV repair. I didn't know he worked on tube stuff. I watched part of the video you linked on my lunch break on my phone. I'll watch the rest the 32" monitor on my desktop. ;) ;) :D

I think I understand about how to establish the crystal frequency. I don't know WHY, though. Then, what frequency do you use to do the osc and mixer alignments? I hope the video fills that part in. Thank you both for your input. :D
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Re: Hallicrafters SX-110

Post: # 17465Post electra225 »

Has any of you heard of Hallicrafters radios with silver mica migration in the IF transformers?
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Re: Hallicrafters SX-110

Post: # 17475Post Dr. Radio »

electra225 wrote: Thu Oct 05, 2023 3:21 pm Has any of you heard of Hallicrafters radios with silver mica migration in the IF transformers?
Any radio that has the smaller footprint IF cans that use "slugs" to adjust have the embedded silver mica caps.

Any IF transformer of that construction...well...as I say, it is not a matter of "IF", it's a matter of "WHEN".

What's going on Greg?

Constant lightning storm noise? What have you checked so far?
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Re: Hallicrafters SX-110

Post: # 17477Post electra225 »

No crashes, no noise. Just REALLY weak reception. I don't own an AA5 that won't outperform this boatanchor, that should have a fantastic front end. I can run an antenna to the next county and it doesn't seem to make any difference. This radio is my bench set and it always performed well in Missouri, where I lived in an area that had poor radio reception. I had a 100' longwire antenna and it performed well. Out here, where there is a station on almost every position on the dial, many of which I get good reception, this set is disappointing. I did a "tune up" alignment on it like I do on other radios to advantage, with really no change in reception. Below about 800 khz, it is especially weak. Seems some better at the higher end of the broadcast band. Forget about shortwave. All that is would be noise. It has been recapped. The tubes are all Hallicrafter branded RCA sourced and all test good. I have subbed the front end tubes with no change. There was a topic on ARF that mentioned that SMD might cause weak reception even if it doesn't make the normal crashing noises. I don't know how to manage this. I'm either doing something wrong or am overlooking something. Next step is probably to dig the chassis out of the cabinet and check some voltages.
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Re: Hallicrafters SX-110

Post: # 17478Post Dr. Radio »

electra225 wrote: Fri Oct 06, 2023 2:39 am No crashes, no noise. Just REALLY weak reception. I don't own an AA5 that won't outperform this boatanchor, that should have a fantastic front end. I can run an antenna to the next county and it doesn't seem to make any difference. This radio is my bench set and it always performed well in Missouri, where I lived in an area that had poor radio reception. I had a 100' longwire antenna and it performed well. Out here, where there is a station on almost every position on the dial, many of which I get good reception, this set is disappointing. I did a "tune up" alignment on it like I do on other radios to advantage, with really no change in reception. Below about 800 khz, it is especially weak. Seems some better at the higher end of the broadcast band. Forget about shortwave. All that is would be noise. It has been recapped. The tubes are all Hallicrafter branded RCA sourced and all test good. I have subbed the front end tubes with no change. There was a topic on ARF that mentioned that SMD might cause weak reception even if it doesn't make the normal crashing noises. I don't know how to manage this. I'm either doing something wrong or am overlooking something. Next step is probably to dig the chassis out of the cabinet and check some voltages.
Yes, there is another form of silver mica disease. I have personally experienced and it drove me nuts before I figured it out.

What happens is the "tabs" that press on the silver substrate loose connection over time. This may be due to mechanical issues, this may be due to oxidation, this may be due to tarnish creeping under the tab growing on the silver mica.

So, instead of a LC circuit, you have added resistance between the coils and the capacitors. You end up with a squirrely LRC circuit.

When this happens, the receiver becomes "deaf". Suddenly strong stations magically move 1000's of miles away....or so it appears.

Here's something to try.

Get something non-conductive, like a chopstick. Pull the chassis out so you have access to the to the lugs under the IF cans. Let the radio run awhile and tune to so-so station. What I mean is, not a flamethrower 50,000 Watt station in your back yard, and not a 1000 watt station 1 state away.

Take the chopstick and start pushing on the solder lugs of the IF cans. Put enough mechanical stress on them it would cause the internal tabs "kissing" the silver on the mica to move.

If the reception "strength" comes and goes, you may have your culprit.

I hope that made sense. I battled this on a 1960 Philco clock radio in which I was absolutely sure I had a bad solder joint on the junky printed circuit board. I kept rocking things on the board and the radio would go deaf, then work properly. I finally touched up every solder joint, and no change. I got really ********* off and finally started grabbing each IF can on the circuit board and rocking them almost to the point I could of cracked the board (hey, I was mad and had enough of this foolishness). Then the a-ha moment. Playing with the transformers housings, caused the reception to magically get worse and then fix itself.
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Re: Hallicrafters SX-110

Post: # 18237Post electra225 »

I tried Doc's suggestion on this radio this afternoon. Nothing really conclusive. I tinkered with alignment and got it pretty good from 700 khz on up, but it is dead as a two-dollar mule from there down. It acts like either the tuner is shorting out, or the oscillator quits running. It is totally dead on the lower end, not even any hash, total silence. I checked the tuning cap for shorts, none found. I measured the oscillator voltage, looking for negative voltage on the grid of the oscillator in the 6SA7 pentagrid converter. I have negative voltage when it is on the low end of the dial, but only two or three volts negative. At the upper end of the dial, I have almost 15 volts negative on the grid of the oscillator. I have subbed all the tubes in the front end, 6SA7, 6SG7 X 2, and a 6SK7 several times with tested good NOS tubes with no improvement. I borrowed tubes from my old SC 1121 and tried them in the Halli with no change. It acts to me like oscillator trouble, but I haven't really found anything that would prove it. I think the oscillator grid voltage is too low on the lower end of the dial, but I haven't found a reason yet. Suggestions? ;)
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Re: Hallicrafters SX-110

Post: # 18264Post electra225 »

I've been reading the service data on this chassis and have come to the conclusion that a good alignment on the oscillator is necessary. I'm a bit confused reading their instructions. "Crystal frequency". What is the crystal frequency? There is an instruction that you do something to something to get the crystal frequency. I'm not clear on what they want. And I'm not clear on whether I have to make that dummy antenna, Figure 9, on the service data.
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Re: Hallicrafters SX-110

Post: # 18274Post TC Chris »

Do they mean a crystal-controlled oscillator for alignment? Or a crystal filter for input to the scope?

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Re: Hallicrafters SX-110

Post: # 18297Post electra225 »

I don't feel so stupid. I get ignored when I post on ARF and this situation is no different. One guy replied but was little help.

I made progress, but I'm not ready to claim victory. It is better. I don't really know what I did to make it better.

Twiddling. I think I fixed it with twiddling. ;) ;)

I try to be a good soldier, get out my schematic, get out the test equipment, warm it up, follow directed testing, follow the diagram.....None of that worked. None of my directed tests showed me anything. The shortwave bands were not dead on the lower end of the dial, they just didn't do much anywhere. I tested and subbed the tubes in the front end, in fact, several times. I took the tubes out of the old SC 1121, swapped them all around. That didn't prove anything. I checked the tuning cap for shorts, none found. I did an IF alignment, just by ear. Not only did that not help, I couldn't make it worse. Then an "Ah-ha!".....

I found one time when I was working with the shortwave bands and turned the function switch to broadcast band. I heard 620, one of our local strong stations. How could the function switch kill the lower end of the dial and not the upper end? I still can't answer that one. I cleaned the function switch really well, then the selectivity switch, then the AVC switch, then all the switches and controls. I can get 620 fairly well, 550 is still really weak, but it is there, also a strong local station. Above about 600 khz, this thing rocks. I can get all kinds of stuff on shortwave, too. I got a station out of Egypt.

I'm not done. I need to figure out why 550 and to a degree 620 are so weak. I had to do everything wrong to get this far. I have no idea what the next step should be.... :oops: :roll:

Another thing I found that I thought was strange. I was running the old Temple TRF set in the shop while I was working on the Halli. I could hear the oscillator of the Halli in the Temple radio. How did I get the oscillator squeal in a radio without a local oscillator? I understood it that you only get that squeal when the oscillator in both radios when you pass the IF frequency. A TRF radio does not have an IF frequency...... :roll:
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Re: Hallicrafters SX-110

Post: # 18299Post Dr. Radio »

Oh boy, Greg.

More random thoughts...I think you may be on the right track on CLEANING everything. Tiny signal voltages don't fair too well when having to cross dirty contacts in band switches, stator connections on tuning capacitors, standby switches, etc.

Clean, clean and "work" the switches and controls. Just don't go nuts with cleaners on phenolic bandswitches. This is always a common warning at ARF about certain chemicals that actually leach into the phenolic parts of the switches and never really evaporate and leave a conductive patch between contact terminals.

I would really give a good Sherlock Holmes look at the tuning capacitor. Perhaps the dial string is putting extra torsional pull on the capacitor at the low end of the band and causing excessive resistance due to some oxidation at the rotor contacts exacerbated by the mechanical stress.

Man that was a random thought!

As far as it being an electronic issue, here is a something to maybe spark some ideas.

https://youtu.be/jQd2LfTOa4k?si=YTFMeYq48ZQZdaw1
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Re: Hallicrafters SX-110

Post: # 18300Post Dr. Radio »

electra225 wrote: Fri Nov 24, 2023 11:39 pm

Another thing I found that I thought was strange. I was running the old Temple TRF set in the shop while I was working on the Halli. I could hear the oscillator of the Halli in the Temple radio. How did I get the oscillator squeal in a radio without a local oscillator? I understood it that you only get that squeal when the oscillator in both radios when you pass the IF frequency. A TRF radio does not have an IF frequency...... :roll:
The Temple was receiving the signal or the harmonic of the Halli.

The Temple is a radio and will pick up a radio station.....the oscillator circuit in the Hallicrafters is a radio station.
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Re: Hallicrafters SX-110

Post: # 18301Post electra225 »

Doc, you may have hit on something. At the lower end of the dial, the knob turns harder, like something is binding. I never really gave that much thought. I was going to give whatever rotating parts in the dial drive I could see a good squirt of PB Blaster. I may do that, then check to see if it made any difference in performance at the low end of the dial. I'll check the link you posted and see if that turns on the light..... ;) :oops: :roll:

Thanks, Doc.... :D
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Re: Hallicrafters SX-110

Post: # 18316Post electra225 »

Good news and bad news. The good news is that I was basically on the right track as to what ailed it. The bad news is that I had to chase my tail to prove that.

The alignment instructions are nonsense. They use terminology that sounds complicated, but is really nothing outside of what you would experience with an AA5. They use a padder for each end of the dial. Both ends were off, but the lower end particularly. The reason I had no reception on 620 or 550, the two strongest stations locally, was that they were tuning together. If you listened real closely, you could hear both stations at the same time. 550 started at about 600 khz and went down to lower than the tuner would go, say, 500khz. 620 started at about 650 and tuned down to about 540 or so. And my conclusion that the oscillator was not running at the low end of the dial was partially true. After I got the oscillator padders set right, the negative voltage on the oscillator grid at the lower end of the dial went from two or three volts negative to just under 12 volts negative. Why did this occur suddenly?

The only thing I can figure is that in Missouri the lowest frequency I listened to was 750. I never really got lower on the dial than that. There was a sports station at 610, but I never listened to it. This condition may have been going on for some time, I just noticed it when I got the radio out here and tried listening to 550, finding that it was "gone".

The radio tunes very sharply now. I found my antenna was broken, so I had to overhaul it. I need to get more serious about having a better antenna. I have to be careful what I put outside, lest the HOA snitches see it. I believe something either in the upstairs or under the soffetts should work. 550 is noisy in the shop on almost every radio I have. I don't listen to that station all that much, but I do on occasion. 830 "The Drive" KDRI, in Tucson is now a local station with the Halli. It comes in better than some of the local stations. I found some ham operators on shortwave this afternoon. They must be running amps of some kind. One guy was in Alabama.
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Re: Hallicrafters SX-110

Post: # 18321Post William »

Congrats, Greg. Now that you have mastered yours, I'll ship you out mine to work on. :roll: :lol:

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Re: Hallicrafters SX-110

Post: # 18323Post TC Chris »

electra225 wrote: Sun Nov 26, 2023 1:35 am I found my antenna was broken, so I had to overhaul it. I need to get more serious about having a better antenna. I have to be careful what I put outside, lest the HOA snitches see it. I believe something either in the upstairs or under the soffetts should work.
The great thing about wire antennas is that they are easy to hide and hard to see.

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Re: Hallicrafters SX-110

Post: # 18324Post maxidyne »

Bill, I did a lot of pure guessing on this radio. Nothing I did in the way of directed testing proved anything. I had to think out of the box. One caveat...the guys on the big forum said my using PB Blaster on function switches was not good..... ;)
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Re: Hallicrafters SX-110

Post: # 18326Post Conelrad »

The crystal freq is not for the local oscillator, rather one in the IF chain to provide a very narrow passband for copying CW.

You have to set the IF transformers to whatever it is as it ages, or gets dirty. It doesn't oscillate, it is just a resonator.

Usually labled as a "Crystal filter" or "Wide-Narrow".

D
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Re: Hallicrafters SX-110

Post: # 18327Post electra225 »

What is "CW" other than a sub-channel to Channel 45 that shows old TV shows. What does CW refer to in a boatanchor? Pardon my ignorance, but boatanchors were my stepdad's gig. To me it's just an unnecessarily complicated old radio... ;)
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Re: Hallicrafters SX-110

Post: # 18329Post Conelrad »

Continuous Wave. The proper name for operating Morse code via radio.

Under crowded band conditions, popular when your receiver was made, the crystal filter could chop the bandwidth down to 300 Hz or so, to eliminate adjacent stations' interference. All you were receiving was pure carrier, interrupted to form the characters.

You have a BFO in that set, a Beat Frequency Oscillator. When properly adjusted, it restores the tones so you could hear it easily.

Those vintage sets were complicated, but those were features, needed by hams and commercial operators.

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