Hallicrafters SX-110: worth the trouble to restore?

[WB3JOK]

I went to the very small hamfest at Hermon (Bangor area), Maine today and a "restorable" Hallicrafters SX-110 receiver followed me home 

It was only $5. A couple of moderate rust patches on the top of the chassis. Cabinet needs a repaint. Original Black Beauties still in place  and there are no tubes.

After a bit of online searching I discovered that 6SC7's are coveted by guitar tube amp enthusiasts. Between Fair Radio and Antique Elect. Supply a tube set would run me about $40 of which $11 is the 6SC7

So - any thoughts as to whether this rx is "worth the trouble" (and expense) to get working again? Is it a drifty POS that will just annoy me after I put $50 and lots of elbow grease into it?

-Charles

ps It's been quite a while since I modified tube circuits like this... is there any reason I can't use two 1N34-type diodes instead of the 6H6 detector/noise limiter?

[N8LGU]

    Charles, the Hallicrafters SX-110 circuit had a long evolution starting as the S-40. It was a relatively inexpensive medium grade receiver consisting of 1RF and 2IF stages with separate local osc and mixer. IF freq was 455kc. It had a S-meter and crystal filter which the S-108 (it's little sister) didn't have. Performance was pretty good-quite a bit of bang for the buck which explains the long runtime Hallicrafters got out of the circuit. No, it's not particularly drifty, certainly not as drifty as, say, the HQ-170. However, the chassis is built light and it doesn't have the authoratative push-pull audio. It didn't have a product detector but SSB could be copied if you kept the RF gain rolled back. (We don't need to listen to SSB, anyway. Do we?)
    All in all, I think it would make a fine AM'er receiver. It's not in the same league as the big guns (75A4, HRO-50, HQ-129X, NC-183D, et al.) But it is certainly worth the effort to fix it up. I think it was one of the best looking Halli receivers.
    Nice find!

[WB3JOK]

I finally got around to working on the swapmeet SX-110 (low 20's and freezing rain/sleet, so no "outdoor" projects). 

That rx has waaay too many "black beauty" caps... replacing them was not difficult, just tedious. Also a mouse had snacked on many of the cloth-braided-covered wires, which I replaced. Thanks to some members here and on Boatanchors, I was able to obtain a complete set of tubes.

I reformed the electrolytic multisection cap (which appears to have been already replaced sometime back in the 70's or 80's) without difficulty. Plugged in the 5Y3, pilot lamps on, checked B+ voltages, so far so good. Installed tubes, powered up, no sound from speaker.  Discovered the output transformer had been replaced by Hammy Hambone with a non-original one (and miswired too). Fixed that. Still no sound. Touched 6K6 grid with a screwdriver - hum in the speaker...

turns out the Sensitivity (rf gain) pot is bad. I could see arcing within it when turning it. Jumpering the pot to ground for max gain, at least I can hear foreign broadcasters on 40m and a couple of 5-land SSBers.  The other bands are still dead but I'll eventually get to that.

The maximum current through the pot (e.g. shunted by an ammeter) is about 30 ma. Does this sound right for the total cathode current of one RF and two IF stages?

Now it's sort of alive. But the round main tuning dial is badly warped and its dial cord is long gone. I need to get it out of there to try and heat/flatten it, but it doesn't look like it'll come out without pulling the front panel... anyone taken one of these beasties apart before?

thanks
Charles

[K4TLJ]

I restored a 110 several years ago and my memory is not that good but maybe I can advise a little. The front panel, as I recall, is removed by taking the retaining nuts off the controls. Then it is easy to restring the dial cord and access the dial. Replace any rubber damper mounts as in all likelihood they are hardened and microphonics will abound. Replacing the 6SA7 with a 6SB7Y will do wonders for 20 meters and up.

[WB3JOK]

OK. In order to get the front panel off I had to destroy two of the three small knurled knobs (45 years of dissimilar-metal corrosion made the setscrews impossible to turn). 

Anyway, the round plastic tuning dial is a real mess. It is severely warped and "burned" (probably from a too-bright pilot lamp) and although I can probably flatten it out with careful heating in the oven, the lower 1/3 of the dial is basically unreadable.

So - can anyone recommend a source for a tuning dial (and a couple of the small aluminum knobs)?

thanks
Charles

[K4TLJ]

Radio Daze http://www.radiodaze.com/reproglassdials.htm lists one but 'out of stock' . Nice folks to deal with. They also have generic knobs.

[oldchief]

Hello, Charles-
   I think you'll like the -110 when you get it back into working condition. its a nice looking set and within its limitations a pretty good performer.
   I have a main tuning dial from a set that passed into the junk box some time ago. Its in excellent condition except its somewhat warped. You can have it if it would help. My email is  jdouglasrichardson@yahoo.com
  73
KB1MCV aka oldchief aka Jim

[WB3JOK]

Thanks for the dial!

Although it's now working, re-capped, and aligned, the SX-110 seems rather deaf on Band 1, and won't receive at all on Band 2. Starting from the antenna terminal, the problem was easy to find since on those bands signal was not getting to the grid of the 1st RF amp.

It seems as though those !@#$% mice did more damage than I thought. 

They snacked on the wires coming off two of the pie-wound coils that comprise the first tuned circuits (on the 1st RF stage grid) for bands 1 and 2. It's not just broken, a short length is completely missing! Naturally the missing end on at least one is at the bottom of the pie, where I can't get to it to reconnect. Looks very difficult to reproduce a pie winding even if I had the Litz wire.

Anyone got a junker that has L2 and L3 (the coils closest to the rear corner of the chassis)? They have "051-201937" and "051-201938" printed on them. Or a source for them?

re-engineering would be a last resort...

thanks
Charles

[WU2D]

6SC7's are around at hamfests for a couple of bucks and even new for 10 bucks. I would not call them rare. Of course on audiophool sites you may find "rare" expensive specimens! Metal tubes are generally not desirable by audio guys. They used the thing for a phase splitter in guitar amps etc... It is essentially an octal 6J6 (common cathode) but without the ultra high frequency or low noise characteristics.

I used one for a Pullen mixer in my SuperPro SX400.

WU2D Mike

[KM1H]

Since that radio traces its lineage back to the S-19/S-20 and thru the S-40, S-85 and SX-99 Id think there are plenty of junker candidates to choose from. There are even some later models that follow the tradition.

For some reason the SX-110 brings suprising prices on Ebay. I picked up a really clean one with matching speaker for $20 a few years ago off Craigs list when I was selling something and the conversation led to it.

Stability is its biggest issue and changing out a few oscillator trimmers with sub mini air variables (I do that to many overhauls) were a big improvement. It currently is my attic daily driver to listen to when Im working up there.

Carl
KM1H

[WB3JOK]

Thanks for the tip. I agree that some air trimmers would be a worthwhile improvement. First I'm going to get it working to stock specs though 

The pie-wound coil is going to be very tricky, although I have managed to locate the very end of the busted-off wire (at the bottom of the pie, naturally). I have to dig up my subminiature 6 watt Oryx pencil iron for that... assuming my hand is steady enough!

The other "dead" coil turned out to be a single Litz secondary of about 10 turns with not one but both ends of the winding broken. That one I was able to fix with a magnifying glass and my fine-tip Weller iron.  So I was feeling pleased with the progress, and decided to look further into the dead band-2 issue. I'd always noticed a lack of background noise and as I suspected, the LO wasn't running on that band... sure enough, my little murine friends had been at that coil too!  I fixed that one as it was also a single-layer winding and the break was at one end.

Now I just have to repair the remaining coil. In the meantime, anyone know what color the cabinet is supposed to be (besides rust)? I'm going to beadblast and primer it, and would appreciate any tips for a "close-enough" off the shelf color.

-Charles

[K4TLJ]

I used  Rustoleum Hammertone gray and primed with Rustoleum auto primer. I also restored a SX-111 and used the same paint. http://home.comcast.net/~suptjud/hallicrafterssx111.htm Sorry all my photos of the 110 are on another PC (unavailable at the moment).

[WB3JOK]

I finally found some time to work on the SX-110 again (currently unemployed, long story) 

So there was just enough Litz wire sticking out of the broken coil (at the bottom of the pie, naturally) that I could gently scrape it clean and using a tiny 6-watt iron, soldered a single strand of 34 ga. wire to that end. Cemented it in place, and ran the strand to the original pin on the base of the form. Put it back in - eureka!

Now it works on all four bands after alignment! Not incredibly sharp, but reasonably sensitive. I immediately noticed that the RF gain has to be kept very low to avoid distortion of SSB signals. Must be the lack of a proper (i.e. product) detector.

Since I have to keep the RF gain down, and the AF gain is already wide-open, is there a tube that I can replace the audio stage (a 6K6) with to get more audio gain without changing anything else?

I also got the recommended Rustoleum paint. Thinking of getting a local body or machine shop to beadblast the case instead of doing it by hand though.

-Charles
ps yes, I know it's an old thread but it's my thread 

[WB3JOK]

The SX-110 is alive with plenty of audio output now... I had the wrong impedance speaker plugged into the jack 

anyone got a pair of the little knurled aluminum knobs (ant trim and stdby/rec)?

I had to destroy the old ones since the setscrews were seized to the shafts.
thanks
-Charles