Hallicrafters S-40 General Coverage Receiver Restoration

Not only have I digressed from my usual focus of European transistorized radios and restored another American set, I’ve restored one with tubes this time. Stop the madness!!

The Hallicrafters S-40 Restored

All self-loathing aside, this was another radio with a $10 price tag in a sorry-looking state that I just had to rescue. Picking it up, I realized this was a true boat anchor, and could probably keep the QE II moored in a hurricane. The fact that it might turn out to be a minor money and time pit totally eluded me at the time.

In my previous restoration of the Heathkit Mohican, I attacked the cosmetic aspects of the radio before making sure I could even get it to function. As this is a potentially dangerous approach, I made sure the S-40 (which did function from the get-go) was going to work before giving it a lick of paint.

Of course, the first task was swapping out the old wax/paper caps for brand new ones. The main tuning capacitor was also gunked up, so a lot of Deoxit was dispensed. On the underside of the chassis, there was a lot of fluff, and probably spider web, woven around the parts. It had probably been collecting since 1946, and gave it that old radio smell. After cleaning that up, I gave the chassis a rub-down with a fine steel wool.

Although the radio was generally functional, I did notice the BFO was not. Looks like a previous owner may have fiddled with it, so I restored the missing ‘gimmick’ that couples the oscillator to the detector stage. Interestingly, I learned that the front panel Pitch control actually turns a coil slug, and alignment consists of taking off the knob and turning the slug until it’s within range of 455 kHz. Then, once the knob is re-attached, a tab on the front panel only allows you to rotate the knob less than 360 degrees to prevent you from going out of range. Unfortunately, this is the most unstable BFO arrangement I have ever come across, so using the Bandspread dial to tune in SSB/CW is recommended.

Speaking of that, I found it counter-intuitive that the higher numbers on the Bandspread dial actually represented a lower frequency. So, I reversed it by flipping over the pulley that was mounted on the Bandspread dial shaft so that the dial string came off the bottom rather than the top. So now, 100 represented the highest rather than the lowest frequency.

After attempting a rough alignment, it was deemed to be functional enough to proceed with the cosmetics. I took the front panel right down to the bare metal, primed it and applied three coats of the finish paint. The main dial window was badly warped and yellowed, so I ordered a new one, along with a decal kit, from Radio Daze. The decals are very delicate, so it was a good thing they gave you two of each. The instructions say that you may want to use clear coat on decals that are next to controls. But let’s be forthright on this; all decals should be clear-coated since they don’t stick to new paint that well. Seven coats seemed to do the job.

The main cabinet didn’t get quite as much love as the front panel, but I did get the worst rust spots out with a light sand blaster. More primer and as much finish coat as need to properly cover it were applied.

The manual recommends doing the final alignment through the holes in the bottom of the cabinet, so once the radio was back together, I started tweaking. The first attempt was puzzling because I could align at one end of each band, but the other was way out. There are also three mysterious trimmer caps for Bands 1-3 accessible through the bottom of the front panel. None of the info I found online acknowledged their existence or purpose, so I gleaned somehow that these were intended to help with ‘tracking’ from one end of the dial to the other. Alas, despite tweaking them and spending a number of hours, I still couldn’t get joy with the alignment.

After some frustration and blue language I calmed down and had an epiphany. I had left the Bandspread dial at the zero position, which, with the aforementioned modifications, meant that the Bandspread plates were fully meshed. Once I opened them completely to the ‘100’ position, the alignment fell mostly into place. Bands 1 and 4 track very well, but 2 & 3 could be better. For those, you just have to choose a range of frequencies that are most important and align to those. As long as I leave the bandspread dial at 100, tuning should be more or less accurate. In hindsight, I may have euchred myself, since the marking on the Bandspread dial says to set it to zero for normal tuning. Oh well.

At the end of this long journey, the S-40 almost looked like a brand new radio. I have to question whether or not it was worth the effort, though. Apart from the satisfaction that comes with properly restoring a radio, I have to say this is a bit of a mediocre performer. A nice-looking, but nonetheless mediocre performer.

Because of its size and performance, this is not a radio I intend to keep. Current prices aren’t great, so no doubt if I were to sell it, I would barely get my material costs back and certainly would take a bath on labour. But then again, vintage radio restoration is about keeping oneself busy, learning about radio history and getting to try out the radios that you’ve known about but never had a chance to take for a spin.

(Almost) The Last of The Mohicans

While I now tend to favour European transistorized radios made in the 1960’s and 1970’s, I can remember as a kid lusting after shortwave receivers like the Heathkit Mohican. Alas, the price was too high for a teenager with an allowance and no job, so I had to settle for a Knight-Kit Star Roamer at the time.

My Restored Heathkit Mohican GC-1A

Fast forward to last fall, and there was a sad (correction…pathetic) looking wreck of a Mohican GC-1A at a local ham flea market, beckoning to me. For $10, I thought I would take a chance on it, even though the S-meter and antenna were missing and the case and chrome knobs were badly pitted. One promising thing was that the dual sliderule dials were clean and intact, and the tuning knobs and pointers seemed to work OK.

First IF Transformer now shielded
and covering the hole in the board

Opening it up, however, revealed more surprises. There was the first IF transformer, sans outer shield, suspended by a few wires above a gaping hole in the board. Did something explode in there, or did the builder get frustrated and punch a hole through it with a screwdriver? Looking further down the board, I couldn’t help but notice a couple of trimmer pots, also suspended by wires above the board. This was going to require a schematic to figure out what was going on, so I Googled the manual and downloaded it.

Series-resonant 455 kHz filters
(circled)

As I was to discover, someone in their lack of wisdom decided to replace two interstage ceramic IF filters with those trimmer pots (!). But it doesn’t stop there. The AVC switch and the dial lights were also miswired. It dawned on me that someone with just enough knowledge to be dangerous must have had a go at this radio as a second or third owner, because the construction was otherwise  good. Maybe when they discovered that pots don’t work well as bandpass filters, they decided to take revenge on the IF transformer? While I didn’t have any three-terminal ceramic filters on hand, I did have some series-resonant two-terminal types that I used as interstage couplers in those same locations. Result.

Battery Pack

So, after sanding down the steel case, priming it, and applying several coats of an automotive aerosol paint (guesswork involved on the original colour), it looks great. Surprisingly, the knobs cleaned right up with a damp cloth, and continue to shine like new. Of course, the battery pack was somewhat corroded, but now functions well. With 8 C cells loaded, I have to say this radio weighs enough to make a good negative-buoyancy marine stabilizer (boat anchor), thanks largely to the steel construction.

S-Meter & AVC Switch

Getting original components is near impossible, so I settled on a replacement telescoping antenna, and had to enlarge the S-meter opening slightly to accommodate one from a cannibalized CB set. To make the meter function logically and properly, I had to reverse the scale card inside the meter and pad it down with a shunt resistor.

Apart from re-capping, one of the last tasks was alignment. Heathkit includes an involved procedure in their manual, and it’s worth following. The only oddity is that the IF tuned fine at 435 kHz, but I couldn’t get it to go to 455 kHz. This caused a bit of head scratching when it came to identifying the image frequencies, but as long as the alignment is done with this knowledge, it’s not a problem.

After completing the alignment, it was time to hoist the antenna and play. Intially, I was disappointed with the gravelly quality of the audio, and SSB sounded somewhat unintelligible at times. My first thought was that the IF alignment was poor and/or the BFO needed tweaking. With no joy there, I looked at the Mohican’s demodulated audio from my RF generator on the ‘scope, and noticed crossover distortion at the speaker. By padding the bias resistors on the bases of the push-pull audio output transistors, the sound is now quite sweet on both AM and SSB. It took a lot of padding, though, so the old germanium transistors were probably getting a bit tired.

Alignment trimmer caps and coils for local oscillator, mixer and front end

Heathkit marketed this radio from the early 1960’s up until about 1968. While it’s not the hottest receiver by today’s standards, it is surpisingly sensitive and stable. That probably explains how this single model remained popular througout nearly a decade. And while I lived with its challenges for several months, now that it is fully functional, the nostalgic value is going to keep it in my collection for some time to come.