Hallicrafters S-41G "Skyrider Jr." receiver
The three-band Hallicrafters S-41G "Skyrider Jr." features full coverage from 550 KHz to 30 MHz. The receiver uses six-tubes and is AC-DC. It is very similar in design to the early six-tube S-38 which replaced it. Tube line-up and function are identical with the use of two 12SQ7's (one for bfo/ noise limiter and one for detector/ AVC/ audio amplifier). Other tubes used for both the S-41G and the S-38 are 35Z5 as rectifier, 35L6 as audio output, 12SA7 as mixer and 12SK7 as I.F. amplifier. The schematic for the S-41G is shown in Rider's Volume 15 and is dated December 1945. The Sams Photofact is in volume (46)10-19. The radio was introduced in 1946.
At the same time, Hallicrafters' Echophone division produced the Echophone EC-1B which is electrically and mechanically identical to the S-41G. Both are updated versions of the Echophone EC-1 .
The Hallicrafters S-41W (white) is also electrically identical to the S-41G (gray) with the main differences being color and knob style.
Safety note: The S-41 and the others mentioned have one side of the power line connected to the chassis by way of the power switch. There are grommets separating and insulating the metal cabinet from the chassis. That insulation must remain intact. For safety, it is strongly recommended that the S-41G (and other AC-DC style radios) be operated from an isolation transformer.
If you must plug it in directly, at the very least plug it into a GFCI (ground-fault circuit interrupter) outlet. See below for a modification for safety with a permanent ALCI (Appliance Leakage Circuit Interrupter) plug and cord and power switch re-wiring.
As purchased, the S-41G was in generally good cosmetic condition but missing the bottom plate. The set was working. The electrolytic had been replaced with four individual caps. No other caps had been replaced.
I replaced all caps that see high voltage including the critical audio coupling cap and the power line cap. Surprisingly, the caps that were replaced showed very little leakage when tested despite the fact that they were early wax paper types. A bottom plate was made for the set.
I replaced the electrolytics once again, bundling the individual caps together while eliminating the in-the-air splices from the prior repair. This was followed up with an alignment.
Safety Modification for the "hot-chassis"
The original design of the set switches one side the power line directly to the chassis. Depending on the plug orientation, that means that the chassis is either live with line voltage when switched on or when switched off (by way of the cold tube filaments.) I decide to replace the power cord with a two-button ALCI plug and cord harvested from a hair appliance. The ALCI plug is polarized. I wired the wide neutral blade directly to the chassis and rewired the the power switch so that the line side is switched to the 35Z5 rectifier rather than to the chassis.
I tested the modification by connecting a ground wire to the ground terminal screw (located next to the antenna terminals). That did not trip the ALCI because the radio's ground terminal has a capacitor between it and the chassis. Moving the ground wire directly to the chassis had the expected result of tripping the ALCI. The ALCI is designed to trip if it detects a ground fault of 4 milliamps.
The S-41G and its Echophone brothers are entry-level minimalist low-cost receivers. Keeping that in mind, the performance of a properly aligned and working set can be surprising. It is a neat shortwave and broadcast-band cruiser. The BFO works well for CW. Tuning SSB can be done but is a challenge since the BFO injection relative to volume cannot be controlled as in a set with a separate RF gain control. The ferrite link bandspread works well for separating short wave stations but only changes the local oscillator a bit and is not as linear as an actual separate tuning cap. Despite its limitations, the set is fun to use.
A manual and schematic for the S-41G can be found on BAMA. The manual for the electrically identical EC-1B is also useful. See the homepage for a link to BAMA.
The "Cosmic Blue" National NC-270 receiver was the previous item on the bench.