Hammond 142B 10K:2K Center-Tapped Open Frame PCB Audio Transformer

The 142B is an open frame, P.C. board mount audio transformer in the 142 Series that steps a 10K ohm center-tapped primary down to a 2K ohm center-tapped secondary, with a 1:0.447 turns ratio. Hammond lists the series for driver, input, interstage and isolation applications, and the part drawing also cites matching and pulse applications.

Power level is 100 mW from 200 Hz to 15 kHz, and frequency response stays within +/- 1 dB (ref. 1 kHz) at both +10 dBm and +20 dBm. Maximum unbalanced primary D.C. current is 4 mA. Total distortion is less than 0.5% for outputs at 200 Hz, decreasing at higher frequencies, and insertion loss is below 1/2 dB. The drawing notes that the secondary may be used as primary and the primary as secondary, so the 142B can also step 2K ohms up to 10K ohms.

Total winding D.C. resistance is 720 ohms on the primary and 210 ohms on the secondary. Typical inductance at 1.0 kHz, 1.0 V is 14.0 H on the primary (pins 1-3) and 3.0 H on the secondary (pins 4-6), with impedances of 68 kΩ and 15 kΩ and a leakage inductance of 1.50 H.

Construction is economical and open type, with pin terminals (0.0375" x .02") on pin bobbins set to a standard 0.187" grid pin spacing for P.C. board mounting. The windings are bifilar wound for balanced capacitive and resistance characteristics, and the insulation test is 1500 V rms. Net weight is 0.5 oz. Dielectric strength is 1500 Vrms; operating temperature is -40 to 85 °C and storage -40 to 105 °C. RoHS and REACH compliant.