Just got a Hallicrafters SX-62A in need of restoration

[AB3FL]

I finally got the SX-62A yesterday.  To my amazement, Most of the tubes are original as they are labeled Hallicrafters and they test good 60 years later.  The top two bands (FM) does work and when I put the selector on AM, it will detect the slope which is good.  Even the electrolytics are good.  The lower four bands including broadcast are dead, which I assume means there is a problem with the 455KHz IF as the 10.7MHz IF is working or I wouldn't pick up local FM.  Any suggestions or caveats would be greatly appreciated.  Here is a pic of it

Thanks All

Tom - AB3FL
 

[KM1H]

The same caveats as the SX-42 apply. TURN IT OFF before you fry something and dont assume the electrolytics are good if original or over 20 years old. Stay far away from no name garbage Chinese electrolytics which are what all the hamfest, small garage and basement vendors sell. Stick to known names such as Nichicon, Panasonic at Mouser, Digi-Key, etc.

Its very easy to fry the bandswitch, power and audio transformers with leaky filter and paper caps, they all HAVE TO be replaced, no half a** repairs in these sets. A lot of resistors will be well out of tolerance also. Replacing a bandswitch wafer is a royal PITA.

I suggest disc ceramic caps as they offer better RF bypassing as well as easier to use and result in a much less crowded chassis. The yellow axial lead film caps are fine for high values as they are often cheaper and in non critical circuits.

Dont shotgun everything at once. Replace the electrolytics and all paper caps associated with the audio including Tone control plus resistors connected to them if needed. Also the ones in the bandswitch sections. Then turn on and be sure an error didnt make things worse. After that I like to do 3-4 caps and associated resistors at a time and continue testing for errors.

Carl

[AB3FL]

I plan on doing all that.  I do have a Sprague TO-6 Tel-Ohmike which can put up to 600V on the caps.  I think that I at lest of the caps to replace the can in my junque box.  Usually I get the parts I need from Antique Electronic Supple as their parts are high quality and reasonably priced.


Tom - AB3FL

[WQ9E]

Follow Carl's advice!  It is a nice receiver and it deserves a little maintenance in its senior years.

A few additional considerations: 

1. Some of the Hallicrafters production has the line bypass caps installed under a cover on the underside of the power transformer.  Even if they have been previously replaced near where the cord enters the chassis check the transformer.  I restored one Halli that had new caps installed near the line cord entry but the original ones were left in place and one burned the insulating paper on the transformer.  The transformer still tested OK but I replaced it with a good parts unit since the receiver was going to an older friend and I didn't trust the transformer after that experience.  Also make sure there is a fuse and it is of the proper rating.

2.  I have yet to restore a SX-42 or 62 that didn't have problems with the mica caps in the FM discriminator.  Maybe I am just really unlucky but I don't think so.  Even a little bit of leakage here greatly impacts FM detector performance.

3.  During alignment you may find one or more of the IF transformers shows a very broad and shallow peak (compared to the others).  This is a good indication that it may also have a bad mica cap inside.  Fortunately modern mica caps are very small and you can take care of both issue #2 and #3 easily without removing the entire IF transformer from the receiver, just remove the can and don't stress the wires to the rest of the circuit.  If you remove an IF can be aware that the thin little piece of insulating paper between the can and the circuit is probably lost most of its original strength so consider replacing it (or a single wrap of quality electrical tape around where the exposed connections are on the base area will suffice).

4..  By now it will be amazing if someone hasn't soaked the switches and controls with some version of cleaner/lubricant.  Hopefully the switches survived this, they generally do.  But the crystal for the filter is likely to need cleaning because any contaminant will create problems.  The older National HRO manuals have good instructions for this procedure.  Basically you disassemble the holder, clean everything with high percentage alcohol, dry with clean paper towel, don't touch crystal element or contacts with you fingers after cleaning, and reassemble.   If you have a signal generator and scope you can test it outside the receiver, tie scope probe ground to signal generator output lead ground, signal generator "hot" on one terminal and scope probe on the other.  You should see a clean and distinct response as you tune the generator through the crystal frequency.  Some of these filters use a ceramic "gasket" between the two halves that is prone to cracking.  Just tighten the screws enough to hold it all together, I saw one that looked like the owner thought he was torquing head bolts on a diesel engine.

5.  Don't forget the little side access panel, removal makes work in the crowded front end much easier.

6.  Careful with the dial scale, the paint is prone to cracking and flaking.  Len Brock made grade reproductions but he stopped several years ago and I don't know if anyone makes them anymore.  There are some differences between the SX-62 generations.

 

[KM1H]

Leave the TO-6 under the bench until after the radio is finished, the only thing it might be useful for is evaluating some mica caps.

I have a TO-6A and military ZM-11 along with some older ones and rarely use them except to check oil and bathtub caps. The Sprague Model 16 goes to 1000V.

The generic electrolytics from AES are the Chinese crap Ive been warning about. Stick to a reputable company, they cater to mostly audiophools these days.

Enjoy.

Carl

[Todd, KA1KAQ]

6.  Careful with the dial scale, the paint is prone to cracking and flaking.  Len Brock made grade reproductions but he stopped several years ago and I don't know if anyone makes them anymore.  There are some differences between the SX-62 generations.

Heed this advice, as even a window that looks fine can have issues. I saw one where a guy gently wiped the back with a damp cloth and took a lot of the white translucent paint off. I've been tempted to shoot mine with clear coat but always stopped short for fear of the drying clear coat peeling and otherwise wrinkling the original dial paint off.

Early models had green and red sections as I recall. Maybe they were colored bulbs for a specific band. Can't recall.

Carl, have you ever come across one of these with a shrunken dial cord as in 'too tight, snaps back after tuning'? Mine seems to exhibit this symptom and could likely benefit from a re-stringing.

[KM1H]

I sort of touched on that in the SX-42 vs 43 thread Todd and didnt define "set up well"

The 62 tuning is OK for most of the time but the pointer backlash and wobble can be a distraction unless its path is cleaned and set up well. Ive not tried a digital readout.

Its not anything I actually resolved since its a PITA and unless the cord was broken I got it as free running as possible and shipped. Customers were happy anyway and would have likely been pissed if I charged more to do a full restring

[AB3FL]

I have replaced all of the paper and electrolytic.  I am trying to align band 6 and think I have an imaging problem.  WPST 94.5 is 50kw about a mile away.  It comes in at 94.5 and about 21mhz below that.  Is there any way to fix that or is it just overloading.  Now the chassis is on the bench with the shed on the bottom removed.  I figure this is also due to single conversion.

Tom - AB3FL

[WQ9E]

Tom,

That image response sounds pretty normal.  The SX-62 is quite sensitive on the VHF range and a 50KW station one mile away is going to have very high signal strength at your location.  Although the SX-62 doesn't have an S meter I would guess if it did your local station would be 50 db over S9 so even with 60 db of image rejection the image would still be close to S-9.

The image should be at 21.4 Mhz. below the correct tuning point.

[Jeff W9GY]

I saw one of these on President Truman's aircraft, a Lockheed Constellation.  Mounted in a passenger bulkhead toward the rear of the aircraft.  Wonder if "give 'em hell Harry: used this himself.

[AB3FL]

How critical are the values of plate and Screen Grid caps?  The radio has many that are 0.022uf, of which I have few.  Can I replace these with a 0.01uf or two 0.01uf in parallel?  Most of them are in the IF circuit.


thanks

Tom - AB3FL

[WQ9E]

Two .01 in parallel will be fine.  Ceramic disc preferable because they are very low inductance.

[AB3FL]

thank you much.  I have a ton of 0.01/500V disc ceramic


Tom - AB3FL