Another in the S-38 Series from 1957-1961 era
I purchased the old radio for $30 from Jim Heye (K5WLQ). I never plugged it in, respecting the fragility of possible old paper and electrolytic capacitors, but the first thing I noticed was that the main tuning dial was strung backwards! The cabinet was nice, with a few nicks and scratches from a normal life — not as nice as I would have liked, but cleanable. The S-38E is the grey hammertone finish; it was also available in S-38EB (beige) and S-38EM (mahogany). It’s a swell example of the era, with the short (pre-1970’s) AM dial and the CD — Civil Defense — marks at 640 khz and 1240 khz.
The S-38 Series was introduced in 1946 (S-38) and were produced through 1961 (S-38E). The S-38E
was produced from 1957 to 1961, making it the end of the line, priced at about $50. Internally,
the radio is a classic “All-American 5”, which makes it very easy to work on. The original S-38 has 6 tubes, but subsequent models have 5.
Tube Lineup for the S-38E, all 9-pin ‘miniature’ tubes — a departure from the older octals:
- V1 – 12BE6 Mixer / Oscillator
- V2 – 12BA6 IF / CW BFO
- V3 – 12AV6 Detector / Audio Amp
- V4 – 50C5 Audio Output
- V5 – 35W4 Rectifier
Left to right: Antenna lugs A1, A2, Ground lug (soldered directly to the chassis!), cw adjustment (Mark II model only), phone output.
Note the use of miniature tubes. Serial number looks to be: 252816, with an over stamped Q42301. Not shown, to the right, the power cord is permanently attached.
The S-38E is a transformer-less radio, and like the S-38B, presents quite dangerous shock hazards.
At some point, however, an attempt was made to isolate B- from the chassis a bit, and to provide for some safety by bridging the B- (ground) and the metal chassis with a 470k ohm resistor in parallel with a 0.06 micro-farad capacitor. However this doesn’t completely remove 120VAC from the chassis or the antenna ground-lug, which is soldered directly to the chassis.
For safety, the switch, which is designed to connect one wire of incoming power directly to the B-, is moved to the other leg, and the newly polarized plug’s ‘neutral’ is placed at the point where the last filament is joined to B-. This assures that (provided the electrical socket is wired properly) the chassis, antenna ground-lug and B- are close to ground.
The power cord is attached to the radio. After a safety rewire, polarizing the cord assures
that the hot leg always is sent to the switch and the chassis-ground is tied to neutral.
This little radio is now receiving on all bands. I’ve received 40m CW and
11m CB. AM Broadcast is strong and clear.
- Radio is tuneable from 540KHz to 32MHz across 4 switched bands:
- Band 1 (AM Broadcast) 0.540 – 1.65MHz
- Band 2 1.65 – 5.1 MHz
- Band 3 5.0 – 14.5 MHz
- Band 4 13 – 31.0 MHz
Completed Appearance Improvements
- Cleaned the cabinet, dials, and knobs.
- Replaced some missing cabinet (back and bottom) screws.
- Finally bought some Bristol Keys to properly remove the knobs.
Always use Bristol Keys (McMaster-Carr #7048A55) to take the knobs off. Hex keys will occasionally ‘work’ to get the knobs off, but they will always destroy the little slug that holds the knob.
Completed Repair Items
- Cleaned the Band Switch, the front-panel switches and Volume Control with De-oxit
- Replaced the multi-stage Electrolytic with a terminal strip and 4 separate electrolytics
- Replaced all the tubular capacitors.
- Rewired the power connection and polarized the power plug for Safety.
Clean scans of schematics are not available via internet, as far as I can find. The usual sources list the user and service manuals, but in some cases only for the ‘non-Mark II’ version. The available Mark II version schematic is a poor scan, in some places illegible. I replaced a tiny mica cap, C16 and if it had been missing or in bad shape, I’d not been able to read its value: 82pf. I plan to take a trip to the Dallas Library Sams Photofacts section for this and a few other scans.
- S-38E Mk II Schematic
- Service and Owners Manual
- A must buy for this and other S-38 series radios is a 10-piece Bristol L-Key Set (McMaster-Carr #7048A55).
These can be found on eBay for around $21 (plus shipping), but McMaster-Carr has the same set for $15.50 (as of Jan 2009)
The S-38E was given to a local gentleman who had contacted the W5FC Club and wanted to try some Shortwave Listening (SWL). I donated the S-38E to the cause, although antenna issues in his location limits his reception. http://www.websdr.org/ fixed that and he is now happliy listening in on CW QSOs all over.
Fortunately an identical S-38E recently replaced it, an almost pristine MKII model, which only required fresh electrolytics and power cord rewiring.