Restoring a Classic 1937 Hallicrafters SX-16 Shortwave Receiver – A Start
It’s been nearly two years since a pair of classic old shortwave receivers followed me home from California, and they have been staring at me each time I enter the shop ever since. Neither are functional, and both are daunting restoration projects. I wanted to revive some of my old vacuum tube chops and collect some vintage test equipment before diving into these beauties. That, coupled with the process of removing 20+ years of clutter, wasp nests and rodent droppings from the shop have slowed me a bit. In the meanwhile, I’ve added to the receiver collection at flea markets and hamfests, so the pressure to make some progress has been building. Time to get started!
The Hallicrafters ‘Super Skyrider” (SX-16, SX-17) was introduced in 1937 and continued until 1938. They are nearly nearly identical with an added RF stage and noise limiter on the SX-17, reportedly the result of a special order for the FCC (Federal Communications Commission). By all accounts, it is a good performer and well worth a restoration. The radio sitting on my bench has obvious water damage besides being over 80 years old. There are numerous waxed-paper/foil and electrolytic caps that will have to be replaced as well as needing extensive cosmetic work. The black wrinkle-finished cabinet is chipped and rusted, the front panel appears to have lime deposits, chipped paint and damaged or incorrect knobs.
The “German Silver” dial is corroded and coated in some sort of sticky finish. The dial legends are nearly obscured by rust and the meter face is cracked. Inside the radio, the chassis is rusted and very dirty. On the plus side, all the tubes are present and test mostly good. The under-chassis is pretty clean, although it is clear that the radio has been repaired/modified in the past. The dial mechanisms still work, and the bandspread dial still freewheels nicely. I’ll have my work cut out for me.
Quick fixes won’t be possible here. I’ve decided on a complete tear-down of the cabinet and front panel to refinish the exterior surfaces. Nearly all the caps will have to be replaced, and we’ll see how the resistors test out. At this point, I don’t have any idea of the power and audio transformers’ condition — but we’ll hope for the best. Removal from the cabinet isn’t hard (other than the weight of the receiver — which is considerable), and removal of the front panel took about an hour.
The silver dial is tricky, requiring a ninja move of removing the loosened panel and dial at the same time. A soak in rust remover for both the front panel and bottom plate helped with rust, but the steel chassis appears to be coated in cadmium (common for this era of receiver). Scotch-brite and fine steel wool helped with the more stubborn corrosion. To my surprise, the dial legends are raised on the front panel, and the removal of rust made them stand out once again. The paint, which appears stippled, is actually smooth on an stipple-embossed steel panel. Masking the legends and applying a thin layer of black paint followed by a clear coat will bring the panel back to near-new appearance.
All but one of the tubes test good, and a replacement was easily found on eBay for $8. The power supply electrolytic capacitors are not stock and were apparently replaced in the early 60’s with a socketed, plug-in can-style capacitor. They test fair, with equivalent series resistance (ESR) of between 4 and 6 ohms, but should probably be replaced. The plug-in style cap is no longer made, but available online, probably used pulls or new-old-stock (NOS). Still, with date codes in the early 60’s, even the NOS caps may be only slightly better than what I have now. I may see if the Hayseed Hamfest can re-stuff the old plug-ins cans.
Looking carefully under chassis, I see several repairs and mods. The “RF Gain” and “Selectivity” controls have both been replaced, and not too carefully. Numerous cold solder joints and messy solder lugs betray other repairs. It looks like other caps were replaced at some point and some connections come apart with just a slight tug.
I have started replacing the old wax caps with new polystyrene ones and it’s not too hard. I’ll have to go slowly though, as some of the connections disappear under the band switch assembly — and it is not easily removed. One other point: I am making sure to get the outside foil on the poly caps oriented towards ground just like the old caps I’m removing. It’s a start. I expect the whole project will take 20-30 hours of work — we’ll see.
How did the project turn out? I have an SX-16 I got out of an estate. Someone changed out the capacitors and it looks like they added a transformer for an 8 ohm speaker. What I don’t like is they removed the two chassis mounted metal capacitors and just left open holes. I found a couple of capacitors in the flea market the same size. I will put those in to fill the holes. They won’t be connected just there to make it look more original. One problem is the top of the cabinet. It is heavily rusted. Fortunate, the front panel is is good shape. I am going to have to physically remove that rust and repaint the cabinet.
I am a little further than the article shows. The recap is about finished, with a few remaining under the RF deck that are hard to get at. The front panel has been repainted and looks pretty good with the legends showing clearly. I have the materials to repair the meter. The hold up has been what to do about the chassis top. It’s pretty rusted, and I got some navel jelly to work on it but am a little nervous to get that on other components. With warmer weather, I can apply the jelly, let it work for a little while and then wash everything off with water, and then let it dry in the sun. Still haven’t decided if I want to remove the tuning capacitor to clean it up — could be difficult to get remounted and operating properly. So, quite a bit of work yet to do . . .
The toxicity of cadmium is evidently extremely bad.
I’m not an expert, but…
I now understand that kidney damage, all sorts of cancers and other serious health impacts are directly linked to cadmium exposure.
Unfortunately, old electronics and many tools and machines were plated with the stuff for decades. It’s become a toxic waste issue.
My understanding is that one definitely one wouldn’t want to be ingesting or breathing even minute amounts of cadmium.
I’ve done a total rethink of my desire to further handle and/or restore old radios and other electronics because of this. Unfortunately, I’ve probably already been exposed to unsafe levels of cadmium via working with vintage electronics.
Extreme care not to release any cadmium in the form of dust etc seems very wise.
Be careful friend.
Thomas
KK7JD
Great project, Jim. have you made any more progress? I also have an SX16 which I’m hoping to get working again. I’ve got a set of caps from Hayseed, Tom, there, even made replica stud-mounting electrolytics for the power supply smoothing. I have all the valves as NOS, but will have to search around for ift cans and a mains transformer. Perhaps a new Hammond mains transformer will be needed. This will take quite a long time but it will be great to hear the set working once again.
Your comment is timely, Peter. I have too many interests and got sidetracked. I’ll get back to it soon though. Yes, the timeframe is a little daunting, but keep up the good work. Good luck! -Jim
Hope to see an update soon! These are great, classic radios.
Hi, Just about to start working on one of these for a disabled friend. Its the S-16 version. Not sure i know the difference. Not looking forward to all those caps.Would like to see how yours turns out.
Thanks for the nudge, Stan. I need to get back to this project. Too many radios, too little time. I can’t promise much activity in the next few months, but hope to get back to it this fall/winter. I do appreciate the interest though! Good luck with your project —- Jim
I just purchased an ebay S-17? ( no Crystal in/out switch) that’s seemingly complete except for missing the bottom panel with holes for alignment access and has different knobs than the “steering wheel” type originals, but the price was reasonable and I am hoping it arrives intact shipping from the west coast to Chicago. When I was about 7 or 8 years old, our father got one for me and my older brothers to play with, and although it was loaned to us for a short time, I was totally fascinated by it, down to the tuning band/log wheel with it’s extending pointer. I decided to take on the challenge of trying to get one working again, it won’t be a 100% correct restoration, as parts are very scarce, but I will try my best to get it back and operating. I would love to see more info on the rest of your work when you get the time to do it and post.
Sounds like a fun project. I’ve been busy with other projects in the last few months, and haven’t gotten back to the S-16, but maybe this winter. Good luck with your project, and let me know how it turns out. — Jim
Ok Jim, I’ve started work on my SX-16. Someone has done a few mods. Mods like, adding caps, and deleteing the doublet wire completely by soldering in a jumper. (I have yet to figure out where the doublet wire originally went) So I am being very careful to verify parts and placement. Lots of caps, and lots of hidden resistors.
Stan
Good luck with your restoration, Stan. Let us know how it goes!
Well Jim, I have it playing but,.. There seems to be a crackling static with the volume down. A good station will drown it out, but it’s always there. All caps (except the micas) and most all resistors have been replaced. Odd thing, the tracking on the broadcast band is way off. An alignment has not been attempted.