Hallicrafters Model S-40B Communications Receiver (1950)

     

This classic shortwave receiver was one of the first "boatanchors" I acquired. I bought it from the son of the original owner, who listened to it until about 1969, then packed it away, where it remained until I bought it in the fall of 1996.

How do I know that it was packed up that long? Take a look at the box it was in when I received it. Despite some chewing around the corners, the box protected the radio all those years. When I gently opened it up, I found newspapers used as padding—pages of the August 12, 1969, Evening Journal from Wilmington, Delaware.

(In case you're wondering, this is not the only box it was shipped in. The seller enclosed this box in a second box, with extra padding, at my request, for its journey across the US.)

This set shows virtually no wear. All of the lettering is in beautiful condition, and there are no chips or scratches.

Description

The S-40 Hallicrafters line began in 1946 and lasted until 1954. With eight tubes, Model S-40 was the mid-level Hallicrafters receiver of the late 1940s and early 1950s. The S-40B was made from 1950-1954 and sold for $129.95.

Below is a magazine ad for the S-40, dating from 1946.

The entry-level receiver during those years was the six-tube S-38, one of the best-selling shortwave sets of all time, retailing for about $40 to $50. If you wanted a top-of-the line Hallicrafters in 1946, you went for the fifteen-tube SX-42, which retailed for $275, roughly double the price of an S-40 and almost six times the price of the original S-38.

The tubes are: 5Y3GT (rectifier), 6SQ7 (RF amplifier), 6SA7 (osc. mixer), 6SK7 (1st IF amplifier), 6SK7 (2nd IF amplifier), 6H6 (detector/automatic noise limiter), 6SG7 (BFO/1st audio amplifier), and 6K6GT (audio power amplifier).

Here's a view of the front of the radio.

The large left dial is the main tuner and the small center dial is the bandspread, which allows very fine tuning. The light green dials are very pretty, in my opinion, and reminiscent of the SX-42. This radio was also available with tan colored dials. To the right of the dials is the rectangular integrated grill for the internal speaker.

The controls in the bottom row are:

  • Sensitivity, adjusts the radio's sensitivity.
  • Band selector, to switch among the four bands.
  • Volume, adjusts audio gain.
  • AVC/OFF, switches automatic volume control, which automatically regulates the audio level for radio signals of different strengths.
  • CW/AM, switches to CW for code listening, AM for broadcast and shortwave.
  • Noise limiter, switches the automatic noise limiter circuit, which reduces noise from electrical interference.
  • AC OFF/Tone, turns on the power and chooses one of three tone settings (high, medium, low).
  • Pitch control, adjusts the pitch for CW signals for code listening.
  • STANDBY/RECEIVE, switches between receive mode and standby mode, for use with a ham transmitter. In standby mode, the DC voltage is turned off, but the tube heaters remain at operating temperature, so you can instantly resume listening.

The top lid of this radio is connected with a long piano hinge at the rear, so to replace tubes, etc., you simply lift the lid and swing it back.

Here is a rear view, with the cabinet removed.

On the back of the radio are terminals for the antenna/ground and optional external speaker, plus a jack for a remote standby switch.

The previous photo was taken right after I bought the radio, before I had cleaned the dust off the chassis.

Restoration

This set received well on all bands during my brief initial test, but like all radios of this vintage, its old paper-and-wax capacitors needed replacement. After sitting unused for almost two years, I finally found time to restore its electronics during the summer of 1998.

The job looked pretty simple. As you can see from the under-chassis view, the electronic layout is uncrowded. (This photo was taken before restoration.)

However, I also noticed a loud buzz from its power transformer. Oh, no! I thought. Power transformers are not easy items to replace. Exact replacements are hard to find unless you have a second, junked receiver handy. And it can cost upward of $100 to have a specialist take an old transformer apart and rebuild it.

I posted a message to the rec.antiques.radio+phono newsgroup asking for advice, and was not disappointed. Almost immediately, newsgroup members answered my question, indicating the cause of the buzz and a variety of suggested cures. The following message thread tells the whole story.

----------------------------------------------------------------------
buzzing power xfmr in Hallicrafters S-40B ?
Author: Phil Nelson
Date: 1998/08/25			
Forums: rec.antiques.radio+phono, rec.radio.amateur.boatanchors 			

The other day I fired up my Hallicrafters S-40B for the first
time since I bought it a couple of years ago.

The radio works wonderfully, but I hear a distinct buzzing
from the power transformer. This is not the usual tube radio
hum. It's not terribly loud, but you can notice it if sitting
close to the radio and playing it at lower volume.

I tested the voltages at the rectifier tube pins, and all are
within 5% of the values given in the schematic. None of
the transformer mounting screws is loose.

Does this just mean that something dried out inside and
has begun to vibrate a little? Since the radio seems stable
and reliable, I'm inclined to live with it unless someone tells
me the buzz is a sign of imminent meltdown. I will recap
the set during the next week or so.

Thanks!

Phil Nelson

----------------------------------------------------------------------
		
Author: nesesu
Date: 1998/08/25

It's probably just a loose lamination vibrating. The varnish can become
brittle with time and heat, and the end lams can come loose. While you have
it out of the case recapping, use a wood wedge and press on the core stack
from the top, midway along each side, and then wedge up from the chassis
along the bottom edges. This should find where the loose one is. Inject some
adhesive such as epoxy into the gap to lock the lamination from vibrating.

Neil S.

----------------------------------------------------------------------

Author: Brokebob
Date: 1998/08/25

Try tightening the four corner bolts that hold the laminations and shield
together.  These are also the mounting bolts.  Have had cases where one or more
of the nuts had worked loose or a lock washer had relaxed a bit.

----------------------------------------------------------------------

Author: CASchwark
Date: 1998/08/25

Yes, there are laminations in the core that are slightly loose due to thermal
expansion/contraction and dried out sealing varnish in there.  Not a worry,
unless it continues to get louder.  Sometimes lightly tapping the exposed core
while running (BE VERY CAREFUL!!) may re-seat the loose ones to kill or
minimize the buzz.

----------------------------------------------------------------------

Author: mike.luther
Date: 1998/08/26

Best solution maybe the trick I always used ..  loosen the screws that
hold the core section together, then go tapping.  At the same time you
can then tighten the screws and check for the buzz.  You usually can get
a particular orientation of tapping and tightening that will cure the
buzz at least for a while or longer..

Mileage varies.. :)

----------------------------------------------------------------------

Author: Radio mf
Date: 1998/08/25

No meltdown, probably a mechanical vibration from dried up transformer. you can
try to open the covers and paint with a laquer or even wedge a small piece of
rubber or wood to quiet it.

----------------------------------------------------------------------

Author: Troglodite
Date: 1998/08/25

Sometimes, this is the result of a loose lamination or two. The common "cure"
was to give the transformer a light whack with a hammer on each of the top four
corners. One of 'em would usually quiet the buzz. If you were a serviceman, you
were cautioned not to let the customer see you do this, as it doesn't look very
professional - but it works about 90% of the time.

----------------------------------------------------------------------

Author: Bill Harris
Date: 1998/08/25			

If the transformer isn't getting hot then it is OK, probably just loose
laminations as suggested in another reply. 

----------------------------------------------------------------------

Author: ED KOWALSKI
Date: 1998/08/26			

....Yes, loose laminations. Fixed many a case like this with a good
swat on the side of the xfmr with a ball peen hammer.

----------------------------------------------------------------------

Author: Phil Nelson
Date: 1998/08/27			

The buzzing transformer has been fixed! Thanks to everyone for the advice.

I was too lazy to take the transformer out, so I decided against the
whack-with-hammer cure, although its simplicity is appealing.
Reminds me of the cure for starter problems (stuck solenoid?) in old
Volkswagen beetles, which is to crawl underneath and give the starter
a mighty whack.

I was able to fix the problem without pulling the transformer. I just
loosened the mounting bolts and worked with it loosely attached.
When all four corner bolts were removed, the looseness of many
laminations was apparent. I brushed varnish on all the lamination
edges, let it seep in for a minute, then brushed on some more.

I had also noticed two unused bolt channels on the long sides
of the transformer. I got two bolts of just the right size and installed
them with locking nuts to help clamp the plates from the middle of the
long sides. (The new bolts don't go through the chassis; they are
installed upside-down with the heads sitting between the chassis
and the bottom of the transformer.)

Then I tightened down all the bolts very hard. In a quick test, the
buzzing was gone! I let the transformer bake under a little lamp
overnight, to dry the varnish thoroughly.

I'm about halfway finished recapping the S-40B, which will be a lot
of fun to use. It's older and simpler than my other boatanchors
(which include an SX-122 and some big Hammarlunds), but
its performance stands up pretty well against them. The only
thing I really miss is a tuning meter. Maybe it's time to find
that old magazine article about connecting an outboard
magic tuning eye to old radios.

Cheers.

Phil

Speaking of meters, not long after finishing that restoration, I published a new article about adding an S-meter to a Hallicrafters S-38; the same principle can be used to add a meter to an S-40B. Another later article described how to add a magic tuning eye to a Hallicrafters S-20R; again, it would not be difficult to adapt that project to the S-40B. Of course, if you are really lucky, you may run across one of the original accessory meters sold by Hallicrafters back in the day; the model number for that meter is SM-40 and you can download its manual from BAMA.

Final Thoughts

If you're new to shortwave listening, an S-40 would make a great first set. There are still plenty in circulation, so you should be able to find a decent one at a reasonable price. And it is an easy radio to fix, as boatanchors go.

Several years after restoring this receiver, I sold it to a fellow who gave it to his elderly father, who had used one just like it many years before.

©1995-2014 Philip I. Nelson, all rights reserved