Emerson Model 678 "Auto-Dynamic" 5 Tube Superheterodyne
Radio Service Data Sheet
April 1934 Radio-Craft

April 1934 Radio-Craft

April 1934 Radio-Craft Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

Emerson Model 678 (Pinterest image) - RF CafeI have been scanning and posting Radio Service Data Sheets like this one featuring the Emerson Model 678 "Auto-Dynamic" 5-tube superheterodyne tabletop radio receiver for many years now. There are still many people who restore and service these vintage radios, and often it can be difficult or impossible to find schematics and/or tuning information.

Emerson Model 678 "Auto-Dynamic" 5 Tube Superheterodyne

Use a high-resistance voltmeter. The figures given are average values taken with a fully-charged storage battery and with no signal being received, The field coil has a resistance of 6 ohms; the potential across the coil is 6 volts.

Emerson Model 678 "Auto-Dynamic" 5 Tube Superheterodyne, April 1934 Radio-Craft - RF Cafe

If the positive terminal of the storage battery is grounded no changes are neces-sary in the receiver when making the in-itial installation. If the negative terminal of the battery is grounded a slight change in the receiver connections is necessary. Re-move the top screw and loosen the bottom screw holding the serial number plate to the right side of the receiver cabinet. Tip the plate down and reverse the red-and-black-marked spade lugs so that the black-marked lug will be on the top, and the red-marked lug will become the lower one. Test for battery polarity by using a low-reading D.C. voltmeter. When connecting the twin-conductor, shielded cable to the battery the black wire always connects to the grounded terminal of the battery, and the yellow wire to the "hot" terminal, regardless of battery



Radio Service Data Sheets

These schematics, tuning instructions, and other data are reproduced from my collection of vintage radio and electronics magazines. As back in the era, similar schematic and service info was available for purchase from sources such as SAMS Photofacts, but these printings were a no-cost bonus for readers. There are 227 Radio Service Data Sheets as of December 28, 2020.