Hammond 143R 25K to 600CT Ohm Chassis Mount Driver Audio Transformer

The 143R is a driver audio transformer in the 143-146 Series matching a 25000 ohm primary to a 600 ohm center-tapped secondary. It is listed for driver applications and, as the only part in this group with a detailed drawing, gives builders of chassis mounted audio equipment lead colors and test data for wiring and incoming inspection.

The 143R is rated for 30 mW with 1 mA of primary D.C. current, and D.C. resistance of 1890 ohms primary and 25 ohms secondary (+/- 15%) in the series table. The drawing's electrical data lists: primary on the RED and BLU leads and secondary on GRN, BLK (center tap) and YEL; excitation current 1 mA max at 28V, 150 Hz; secondary no-load voltage at 28V, 1 kHz of 4.353V ±2% GRN-YEL and 2.176V ±2% from each end to BLK; DCR at 20 °C of 1.84k ±15% RED-BLU and 21.03 ±15% BLK-GRN; and a 250V, 60 Hz, 1 second primary-to-secondary hipot. Drawing dimensions are A 1.266" ±0.031, B 0.690" ±0.125, C 0.690" ±0.031 and D 1.063" ±0.031.

Mechanically, the 143R is a small, economical open type transformer with a two hole horizontal bracket for chassis mounting and series-table overall dimensions of A 1.26 in (32 mm), B 0.69 in (18 mm), C 0.69 in (18 mm) and D 1.06 in (27 mm). It uses insulated, color coded flexible leads at least 4" long, and net weight is 0.5 oz. Where a P.C. board mounted version of this style is needed, the manufacturer refers to the 148 and 149 series.

Frequency response is 150 Hz to 15 kHz within +/- 1 dB, referenced to 1000 Hz. The manufacturer notes that operating at impedances below nominal lowers power capability and frequency spectrum proportionately, while higher impedances raise them. It follows schematic 2 in the series table and is listed as RoHS and REACH compliant (UPC 623980191508).