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Hallicrafters Items

 

Production Year 1947 - 1953 at $49.50 

This Hallicrafters S-38B is the third version of the S-38 family that was originally released in 1946. The Hallicrafters S-38 line included the models S-38, S-38A, S-38B, S-38C, S-38D, S-38E, S38EB and S-38EM. There are two versions of the S-38 without a letter suffix that is known to exist. The original S-38 had 6 tubes, a metal bottom cover and a smooth black finish on the cabinet. The second version of the S-38 which started production just prior to the model S-38A, had only five tubes, a cardboard bottom cover and a black wrinkle finish on the cabinet. All of the later models were essentially the same as the S-38A with the difference being the color and finish on the case and dials, some back panel changes and the way the power cord was attached. Although the C model used a 12SG7 tube rather then a 12SK7 tube as the IF amplifier. The A model had a smooth black finish, the B model had a black wrinkle finish, the C model had a Hammartone gray finish, the D model had a smooth gray finish, the E model was a smooth gray, the EB model had a beige finish while the EM model was a mahogany color. Beginning with the S-38D Hallicrafters radically changed the look of the receiver. It no longer had the half moon shaped dials, but rather a large rectangle frequency display very much like the Hallicrafters 5R10A. Starting with the E models, Hallicrafters added a BFO injection control on the rear apron of the chassis and changed the tube line up a bit. The Hallicrafters S-38 series of receivers remained in production from 1946 until 1961, an unheard of time span by the standards of today.

The Hallicrafters S-38B is a Superheterodyne, general coverage receiver that is used for the reception of AM and CW signals. The S-38B receiver incorporates 5 tubes in its circuit and has 4 bands with continuous coverage from 550 KHz to 31 MHz. The first band covers 550 KC to 1650 KC, the second band covers from 1.7 MHz to 5.1 MHz, the third band covers from 5 MHz to 14.5 MHz, and the fourth band covers from 13 MHz all the way up to 31 MHz. The Intermediate Frequency(IF) of this receiver is the standard 455 KHz. The internal roof mounted speaker is of the permanent magnet moving coil design that measures five inches across and has a voice coil impedance of 3.2 ohms. Received signals exit through a perforated section on the top of the unit. If headphones are to be used, the receiver requires a set with 500 to 2000 ohm impedance. This radio uses the standard #47 bulb for the dial lamp.

The Hallicrafters S-38B also features band spread tuning. The band spread dial is located to the right of the larger main tuning dial and is calibrated from 0 to 100. To operate the band spread dial, set the main tuning dial to the high frequency limit of the range of frequencies to be covered and then tune stations in with the band spread control. For example: say that the 40 meter amateur band is to be covered. Set the main tuning dial pointer to 7.3 MHz and tune in the stations with the band spread control. The band spread control allows for fine tuning of stations and forces the operator to move across the frequency spectrum at a much slower pace, thus helping to insure that weak stations are not missed. Tuning the bandspread control from 0 to 100 tunes the receiver progressively lower in frequency. One thing to keep in mind is that the calibration of the main tuning dial will only be correct when the band spread dial is set to zero.

The photograph above on the left is of the front of the radio. Scanning across the front panel from left to right, the operator controls and their functions are as follows: at the top left is the Main Tuning knob, at the bottom left we run into the first of three front panel switches. This first switch is used to select the desired receiving mode and is labeled A.M. on the top and C.W. on the bottom. The next switch that we come to allows the operator to select between the internal Speaker or the use of Headphones. In the center of the receiver is the four position Band Selector knob that is used to select one of the four bands for reception. Next we run into the On/Off and Volume control knob. From here we move upwards and find the Bandspread knob. At the bottom right hand corner we have the last of the three switches which is labeled Receive on the top and Send on the bottom. The Send/Receive switch removes the plate voltage from the tubes of the S-38B which makes the receiver inoperative during times of transmission. This switch can also be used to conserve power during a stand-by period when it would be important to have the radio spring to life with just a flick of a switch instead of having to wait for the tubes to warm up.

The 5 tubes that are used in this receiver along with their functions are as follows: 12SA7 = Converter, 12SK7 = IF Amplifier & BFO, 12SQ7 = Detector and Audio Amplifier, 50L6GT = Audio Output, and a 35Z5 employed as a Rectifier. The power source requirements are 105 to 125 volts DC or between the same voltage range but with 60 cycles AC. The normal power consumption of the receiver is 30 watts. It is also possible to operate the receiver from a 210 to 250 volt AC or DC power source by using a special line cord adapter with the Hallicrafters accessory part number of 87D1566.

The photograph above on the right is of the back of the radio. The connections and such found here are as follows, from left to right, 3 terminal antenna connections, serial number, headphone connectors, and at the right is the power cord. The text that is printed on the right side edge of the back panel directly above the power cord reads as follows, "CAUTION This interlock plug is provided as protection against dangerous electrical shock. Do not tamper with the interlock or attempt to operate receiver with the back off. The chassis of this appliance is connected to one side of the line.". In short, with the back panel removed it also removed the danger from electrical shock due to the power cord being disconnected. The model S38A does not appear to have this safety design. According to the 1953 book "Television and Radio repairing" by John Markus servicemen would use what is called a "cheater cord" to operate the set when such a safety device was built into its design. This cheater cord allowed the serviceman to operate the set with the back cover removed.

The 3 terminal antenna strip on the back panel is marked "A1", "A2" and "G" and known as Antenna 1, Antenna 2 and Ground. A jumper bar consisting of a strand of wire is normally connected between terminals "A2" and "G" for single wire antenna systems as well as unbalanced antenna transmissions lines. For a doublet antenna system with a balanced transmission line, the jumper between "A2" and "G" would be disconnected and the transmission line from the antenna would be connected to terminals A1 and A2. If a concentric transmission line(coaxial cable) with a grounded outer conductor is used, connect the inner conductor to terminal "A1" and the outer conductor to "A2" followed by a jumper wire between terminals "A2" and "G". The station ground connection is to be connected to the "G" terminal.  

The photograph on the left is of the rear of the receiver with the back panel removed. This picture displays the tube compliment and some of the other major components that are found on the top of the chassis.

The photograph on the right is of the bottom of the S-38B with the bottom cover removed. In this picture we can see the entire "add the solder by the inch" circuitry. This radio design is just a slight step up on the evolutionary scale from the all American five receivers. In other words, they are not that complicated and there is a lot of room to move around. The little orange things are capacitors and are commonly referred to as "orange drop capacitors". It is often recommended to replace all of the molded paper and waxed paper capacitors in these older receivers which has been done for this restoration. The reason being is that over time the old capacitors may start to dry out and become open, shorted or leak which can hurt the performance of the receiver and possibly cause serious damage to some of the components.

Also notice on the left hand side that new electrolytic capacitors(3 blue things) have been installed as well. Some times when I do these restorations I will drill out the gunk from inside the old original capacitor and stuff the new replacements inside. I normally do this so that the radio would keep its original appearance. Capacitors that are made today are not only sturdier and more precise, but are also much smaller. A capacitor from yesteryear that was the size of a roll of quarters is now the size of a pencil eraser today. In most cases, the new replacement capacitors will easily fit inside the body of the old capacitor. Some folks have been known to take this a step further and go so far as as to even stuff both the waxed paper and molded paper capacitors to give the set a museum quality restoration. As an added touch I have installed heat shrink tubing over all of the bare wire on the positive side of the electrolytic capacitors. The heat shrink tubing can be thought of as carpenters caulk, it gives the work a nice and neat appearance. Did you notice that all of the electrolytic capacitors have the same ground connection? Before I solder any wires or leads to the chassis or to the tube pins, I clean the oxidation and other gunk from the connection point with a Dremel tool using a wire brush attachment to clean the connection point.

For a much better restoration job I could have done a little re-wiring and installed a fuse between the AC power cord and the on/off switch. For a proper restoration one should install both an X and Y type capacitors across the power line(X type) and going to ground(Y type). Should one of these safety capacitors(X or Y) fail they are designed to open. Should an orange drop capacitor fail it could create a short circuit. The orange drop capacitor seen in the lower left hand corner should be replaced with a Y type capacitor.  

  

  

If the cabinet is ever removed from the chassis, the rubber grommets, fiber washers and nylon insulators should be inspected and replaced if they are damaged. It is very important that the cabinet be insulated from the chassis. WARNING!! It is very important that you do not rely on these insulators a half a century later. A lot could go wrong such as, are they still in good condition, did a previous owner reassemble the radio properly, and so on. With these AC/DC sets, depending on which way the power cord is plugged into the wall can put the entire receiver at 120 volts above ground. This means that if the operator has one body part resting on an earth ground and reaches over and touches an exposed part of the receiver, the operator can receive a potentially fatal shock.

The partial schematic above is for the Hallicrafters S-22R receiver. This schematic would feel right at home with many of the AC/DC receivers, or numerous other electronic items that are built this way. There is no power supply transformer in the circuit of these items which makes them dangerous if the operator becomes careless. Actually, the reason the set can run from a DC power source is because there is no transformer. Today, an item built this way and with a metal cabinet would never get past the Underwriters Laboratory(UL). In fact, if you were to take a survey of the electrical items in your house, what you will most likely find is that just about every appliance with a metal case has a three prong power cord attached to it. As seen in the schematic above, the item will work no matter which way it is plugged into the wall. One way allows the chassis to be connected to the hot wire in the home wiring, while flipping the plug the other way connects the chassis to the neutral side of the house wiring. Either way can be dangerous as both the hot and the neutral house wires in the U.S. carry current. Even though at the fuse panel both the neutral and ground wires go to the same place.

Picture this, the receiver cabinet is hot with 120 volts of AC. You have a hand resting on a desk lamp that uses an older non-polarized power cord or is grounded by a newer 3 prong plug, or your hand is resting on the station ground, or your feet are propped up on the heater, or a thousand other possible ways you could easily be at ground potential, now you reach for a switch on this radio and ZAP, the current runs through your body as it makes its way to ground and kills you. Now your wife becomes a widow and we see your stuff listed at auction under the title "From the estate of a SK". I realize that this sounds harsh, but in most cases there are no second chances. What's that I hear you say? You fully understand the dangers and will watch out for this? What about a family member when you are not home? Do they also understand the danger? Do not risk it. Explain the dangers to them and check the voltage on the chassis with your VOM with the on/off switch in both positions. An isolation transformer can also be used, or better yet, unplug the device when you are away.

  

  

Resources:

Radios by Hallicrafters with Price Guide by Chuck Dachis

Hallicrafters owners manual

Sam's photofacts by Howard W. Sams & Co., Inc.

Television and Radio repairing by John Markus     

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