AMRAD Model 81 ("Bel Canto" Series) Receiver
Radio Service Data Sheet
June 1930 Radio-Craft

June 1930 Radio-Craft [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.

The Model 81 chassis is fused at three amperes. The "antenna compensating control" is the 10-plate variable condenser marked CIA; while while the remaining trimming condensers are adjustable, through the shield can, with a screwdriver. Binding posts at the rear of the chassis permit selection of the correct tap on the antenna input inductance L1 , for the required degree of selectivity and sensitivity. When the tube is renewed at V4, it will probably be necessary to readjust the setting of R8. If circuit oscillation should appear in the receiver, it may usually be traced to a defective '24 tube, which should be replaced. The cord which operates the tuning dial is kept in tension by an adjustment which compensates for stretching; this is regulated by putting a screwdriver through a hole cut in the edge of the dial drum. Each of the R. F. transformer primaries (Ll1, as well as P in L2, L3 and L4) consists of a winding of about 200 turns on a bobbin at the grid end of the secondary; it has a direct-current resistance of about 80 ohms.

AMRAD Model 81 ("Bel Canto" Series) Receiver

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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.

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