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 Post subject: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Mon 13, 2017 4:01 am 
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Location: Costa Mesa, California
I wanted to get one of these for a while. They are usually out of my price range and look to be in terrible shape. The front panel trim piece around the dial face is fairly light gauge and dents easily. This one I was able to get at a good price and pick-up from the seller--saving shipping and potential damage. It does not have the correct knobs at two of the locations--however, I am fine with the spinner. The dial pointer adjust can be swapped out for something a little closer to the original. This radio is really dusty, but otherwise in nice condition. It has a few add-ons but no holes were drilled and all the other parts appear to be there. Right now I am cleaning it up.

If you look under the radio, there is a shield soldered on over the IF section. Is this original? It would make adjusting some of the trimmers and transformers difficult and obviously would need to be removed to change out the caps. Upon replacement, I would hopefully just screw it in place.

The SX 62 looks just like my SX 42 in many, many ways--except it doesn't have a bandspread capacitor and no shield plate over the main tuning and RF section. It has a crystal calibrator--that is nice. The crystal says 500 on top, so I assume it is a 500 KC calibrator. The big question I have is whether an external bandspread is a possibility? The added capacitance of the wire exiting the radio may make it not practical--but I wanted to ask if such a thing was ever tried either for this radio or another radio. It would tie in where the small tubular ceramics are now above the chassis attached to the main tuning cap. If a person were to add a bandspread--would they necessarily need to do it for all sections of the main tuning or just the oscillator and maybe the mixer.

Norm


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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Mon 13, 2017 4:34 am 
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You're right, Norm. It looks like Hallicrafters just left the bandspread cap and circuitry off an SX-42 chassis and shipped it out the door - with a new front panel and tuning gear of course.

Thanks for the inside pix, as I'd not seen that view before.

I'll be following your adventures, as usual, as I continue my SX-42 project, er..., career.

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Mon 13, 2017 1:37 pm 
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Norm,

My first week as a novice I used a SX-62 as my station receiver. Using the crystal filter on the novice band involved leaving the front cover up and using hand capacitance near the front section of the tuning capacitor for fine tuning. It seemed reasonable to a 14 year old at the time :) Upgrading from that to a SX-101 definitely changed my novice operating activities.

I have never seen that shield on any SX-42 or SX-62 that crossed the bench so probably an owner addition. IF stability has never been an issue in the SX-42/62 series so I have no idea why the owner felt the need but keep an eye out because you might find other modifications (i..e. changed components to increase IF gain).

The SX-42 and SX-62 are nearly identical, the mix of octal to loctal tubes changed a bit depending upon the version of the SX-62 but the receiver design is nearly identical. Obviously the band spread makes the biggest difference in the SX-42's ability to function as a ham receiver and the front panel BFO and phasing adjustments along with S meter also contribute to its utility. The only circuit advantage the SX-62 has is a built in calibrator. Cosmetically they are both attractive receivers with nice audio sections.

One of my ARRL handbooks has the multi-page ad from when the SX-42 was being closed out and it was only $5 more than the SX-62, quite a relative bargain. But visitors to your radio room will be instantly drawn to that big slide rule dial of the SX-62. If I had been the original cosmetic stylist it would have had a magic eye tube where the Hallicrafters h logo sits.

Have fun but I don't suggest it as your station CW receiver above 80 meters :) Maybe the perfect co-receiver for a SX-101A to provide BCB and general coverage shortwave along with coverage of 160 meters.

Rodger WQ9E


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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Mon 13, 2017 2:09 pm 
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Location: Wood River, Ill.
I picked up a SX-62 15 or 20 years ago. It was in so so condition, needing the usual recap and routine go thru. As I recall, the dial cord needed to be restrung. Having gone thru all of the above, I had it out of the case and in playing condition, when I came back to the shop one evening and it would not tune. The dial string was broken again! A mouse got into the chassis and chewed thru the new dial string. Changing bands revealed that the mouse had also gotten under the chassis and started feeding in some of the coils. Apparently they really like the wax used to seal the coils. :cry:
The radio was stored away, waiting on finding some replacement coils, some traps were strategically placed, and the hunt was on for a parts rig. I did find a parts doner a few years ago, but the SX-62 has not made it back to the bench yet. As I recall it was a nice sounding rig, until it was “mouse modified”. Good luck in your restoration. I will be following along. Maybe it will motivate me to place mine back on the bench. :D

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Tue 14, 2017 5:42 am 
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Location: Simonton, Texas
I did one of these a few years ago and mine had the soldered on shield over the coils. It also had a bad cap

in one of the FM transformers. It also had a lot of Red Chief (I think) caps. I may have a few spare knobs

I could donate as I have a parts unit that got dunked when my house flooded but the knobs should be ok.

P.M. me should you need any the knobs or any other parts.

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Wed 15, 2017 12:37 am 
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Koby, thanks for the offer. I may get back to you on the knob. When I google SX 62 images, I see there were different knob styles at different times for the various SX 62 types. The one knob I want is the dial pointer knob on the upper left. My radio has a knob that looks like it would be for the other SX 62 type. I did find a pretty good match on eBay and will wait until it comes in. The tuning knob is a spinner on my radio--which I have no problem with. Although not original it was a common practice to use those knobs back when the radio was recently purchased--and so, I find it of historical interest. If modifications were made to radios fifty years ago, and the modifications were reasonable, I don't feel the need to restore the radio to factory conditions. I actually find the modifications valuable--both for historical reasons and for practical reasons.

Norm

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Wed 15, 2017 1:57 pm 
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Norm...I picked up one of these several years ago, when I first saw it at a hamfest, I could only describe it as Doctor Frankenstein's personal SX-62. It was heavily modified, holes everywhere, with a number of 1/2" diameter yellow multi-conductor cables wrapped around it. The bezel and slide rule dial were hand-marked up in dozens of places, as if the original dial was not 'busy' enough.

The owner did install a large bandspread tuning cap in that big open area of the chassis, not externally. If I recall correctly, he used the dial pointer reset panel hole to feed out the bandspread tuning mechanism shaft and he put a large knob on the end of it. Who knows, the cap may have been from an SX-42. It was the same relative size as the main tuning cap and except for his mechanical tuning mod, it looked like it was an SX-42 factory capacitor.

I would imagine that that this could be done externally, however, shielding, cabling and drift may be of concern when the BFO is on.

I also have a mint SX-62. My only gripe would be (probably already mentioned) the touchy main tuning performance, especially with the BFO on, obviously. I wondered at the time when buying the modified SX-62, why someone would hack up a receiver like he did. Of course, I had to have the SX-62 and I hand carried the unit across the fairgrounds, 270 yards to my car.

With the bandspread added, the Frankenstein receiver performed well while tuning and of course the audio sounded excellent in the AM and FM modes....just too damn ugly to put on display...

Todd
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Last edited by KA8GEF on Nov Wed 15, 2017 2:51 pm, edited 1 time in total.

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Wed 15, 2017 2:44 pm 
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A fairly easy and reversible modification for the SX-62 would be to place a small variable cap (in parallel with the oscillator section of the tuning capacitor) in place of the current pointer reset mechanism and this would allow easy fine tuning coupled with the ability to correct calibration. The National HRO-50 and 60 utilize this approach for calibrating the slide rule dial but users quickly discover it is also very handy as a fine tuning control on the higher bands.

If you add tis variable cap limit the size to a few pf because you don't want to move the oscillator far from the other sections because sensitivity will drop; this is the same problem some low cost receivers run into because instead of using a full band spread capacitor only a single oscillator section is used and the front end circuits don't track with the band spread. However a small added variable cap would make this receiver somewhat more usable for ham radio use on CW while using the crystal filter. You will also find that just using the pointer reset mechanism as installed will cause a noticeable frequency shift when the BFO is on.

And please use good practices if installing this mod. Don't add new holes and store any removed parts with the receiver so that you or the next owner can make it fully stock again.

Finally for those who want to use a classic receiver like this in conjunction with a transmitter for a vintage setup adding an external converter for the ham bands will allow excellent modification-free enjoyment. Mobile converters from the 50s era are readily available and cheap so keep an eye out for one of the classic Gonset, Morrow, etc. units at your next hamfest. My favorites is the Morrow 5BR shown in the upper left of the photo sitting next to the Morrow FTR (fixed tune receiver) which could be combined with the converter to provide a nice portable/mobile station receiver when you didn't want to tap into the car's broadcast set. I think of my Morrow Falcon as the compact mobile ham counterpart to the SX-62, beautiful styling with a nice sliderule dial in a mobile/small form factor.

Rodger WQ9E


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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Wed 15, 2017 3:02 pm 
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Rodger, great looking Morrow collection! I hope to pick up the receiver one day. I have the Elmac PMR-8 and Pierson KE-93 mobile receivers. I recall someone having and comparing the Gonset, Morrow MB-6, Elmac PMR-8 and Pierson mobile receivers and in his opinion, the Morrow was the best overall performer....great find!

Todd
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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 6:37 am 
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One thing, I find odd is that there is no pitch control for the BFO. Does this mean the radio can not work for SSB? Another odd thing is the crystal filter has a null capacitor--C57, but it is not brought forward so that it can be used and is set once for several KHz off the center frequency and then never moved after that. Why have it there at all? In fact, looking at my under-the-chassis picture again, I don't see that there is a C57 as shown in the schematic and referenced in the manual. Until I get back to the radio on the bench, I am starting to pile up mysteries that will need to be solved.

Norm

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 1:20 pm 
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You will find that with the tuning backlash and the mechanical and electrical instability of the SX-62 series that they aren't well suited for SSB. The SX-42 is better in this regard but still not a great SSB radio.

With the SX-62 the IF bandpass is wide enough that you will be able to tune both USB and LSB with a fixed BFO setting but it will be suboptimal. My suggestion is set the BFO for optimal LSB reception in the medium xtal position because on 20 and up, where you will find USB, the tuning rate and lack of stability make it not worthwhile to try SSB. It will work pretty well for SSB/CW on 160 and 80 and depending upon your definition of reasonable it is possible on 40.

Or if you really want decent SSB on the SX-62 couple your highly stable signal generator into the antenna input so that the BFO function occurs at RF rather than IF. You do the fine tuning with your signal generator and as long as it and the transmitting station are stable the SX-62 can drift or jump quite a bit without you noticing it since the frequency relationship between the transmitting station and the "artificial replacement carrier" provided by your signal generator remains the same regardless of what the SX-62 HFO does.

Rodger WQ9E


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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 2:21 pm 
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Norm...the SX-62 series was certainly not designed for ham band use, in the manual you may find more info on tuning shortwave stations or inputting a phono, than copying CW or SSB. It was a receiver that one would put in his den and fill the room with several watts of MW, shortwave or FM audio. JFK had one in Air Force One for monitoring shortwave broadcasts and world opinion on the Bay of Pigs invasion, communist aggression etc.

There is a BFO oscillator. The later runs used a 6J5 as the BFO oscillator, if I recall correctly. There is probably one inductor in the 6J5 grid circuit that is variable (no variable cap brought to the front panel). When switched to 'code' mode, the BFO oscillator injects that fixed signal into the IF (peaked at zero beat) and the user tunes the main tuning (signal) to one side of zero beat, typically 650-800 hz for CW copy. The same theory holds for single sideband, of course.

That cap you are referring to (C57) may have been removed at one point in time during production runs (or by the owner) because it added too much capacitance to the phasing circuit or affected crystal frequency. That is of course a guess.

Rodger WQ9E is well versed in the SX-62 series receiver, feel free Rodger to correct me on any of the above....Norm, I have an SX-62 MK2A digitized manual copy (somewhere) that is much clearer than the 'fuzzy' manuals floating around, if you need one....

Todd
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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 2:46 pm 
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Todd,

I agree completely with what you said. The SX-62 is very good at its intended purpose which is a sophisticated receiver for listening to broadcast stations across the spectrum and not as part of a ham radio setup.

Rodger WQ9E


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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 5:11 pm 
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It looks like I was typing at about the same time Rodger was posting, sorry for some of the duplication of comments...lol

Todd
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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 5:54 pm 
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Thanks for the answers. I am not planning on using this for SSB reception, but was curious about how the radio functions--and I am quite interested in seeing what Hallicrafters did when they took the SX 42 and just changed a few things to make it a SWL receiver. The outer case came back from the powder coater yesterday so this weekend should see some progress toward a beautiful radio.

Norm

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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Thu 16, 2017 7:02 pm 
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Norm...hope to see that cabinet when it comes back from the powder coater. Also if you need a very clear copy of the MK2A manual......I found the file.

Todd
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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Sun 19, 2017 11:56 pm 
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The cabinet came back from the powder coater on Thursday so this weekend, I re-capped the radio, aligned it, added a three-wire cord, and fired it up. Wow, was the music sweet. My favorite classic music station sounds so good coming from this radio--much better than either of my SX 42's.

As for the filter, I spent a lot of time thinking about it the last few days, but when I went to employ all my new-found understanding--it did not go that well. I guess I am just as confused as before. There is a variable phase trimmer, but it is located under the chassis and can be adjusted by reaching down from the top with a screwdriver. Half the problem was getting the rotary switch for the filter positions to work well. It is hard to compare output levels when the switch contacts are intermittent and a lot of wiggling is involved. The way I understand the instruction is that a person is asked to first move the transformer secondary coil, S10, off the crystal frequency by about 1KHz, then set the null another 1 KHZ further off to get it out of the way, and then adjust the sharp trimmer to bring the resonance back on the crystal frequency, and then detune 2 db. The middle crystal position has a trimmer that finds a position half way between the weaker broad position and the stronger sharp position. I really need to look at the passband with a spectrum analyzer to know if what I think I did is really right.

Here are the pictures.

Norm


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 Post subject: Re: Hallicrafters SX 62 Mark 2A
PostPosted: Nov Mon 20, 2017 12:41 am 
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Wow, that cabinet looks great!

I'll be looking to see if you conquer to filter alignment. No luck here so far on the 42.

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