4000 to 500/2000 Ohm Driver Transformer, PCB Mount

The 148K is an open-frame audio driver transformer for printed circuit boards with a 4000 ohm primary and a dual 500/2000 ohm secondary. It is part of the 148 Series of audio open-frame transformers and is aimed at designers and OEM builders who need a board-mounted driver transformer in a small signal-level audio circuit.

Its part drawing adds production test data: excitation current of 1.2 mA maximum at 13V, 400 Hz on pins 1-4; secondary no-load voltage of 4.600V +/-2% on both pins 5-6 and pins 7-8; D.C. resistance at 20 degrees C of 495.5 ohms (pins 1-4) and 101.6 ohms on each of pins 5-6 and 7-8, +/-15%; and a primary-to-secondary hipot of 250V, 60 Hz for 1 second.

The transformer uses economical, open-type horizontal bracket construction with pin terminals 0.25 in long and 0.025 in square for P.C. board mounting. Windings are bifilar wound for balanced capacitive and resistance characteristics, on pin bobbins for standard 0.2 in grid pin spacing. Pins are not labeled; a dot marks pin 1, and the remaining pins follow from the schematic. Net weight is 0.6 oz for the 148 Series.

Frequency response is 200 Hz to 15 kHz (+/- 1 dB, referenced at 1 kHz), insertion loss is less than 1/2 dB and the insulation test is 250V rms. Total distortion is approximately 2% for drivers at 200 Hz, decreasing at higher frequencies. The 148K is RoHS and REACH compliant. For rugged epoxy cast units the manufacturer refers to its 102, 104, 106 or 107, 108 and 109 series.