Hammond 1750F 15W Blues Junior Output Transformer, 8 Ohm

The 1750F is a 15 watt push-pull output transformer for tube guitar amplifiers, designed as a drop-in replacement for the original unit in the Fender Blues Junior and Pro Junior. The series ordering table lists it as similar to Fender part number 49969, making it a practical choice for repair technicians servicing these amps.

It couples a 6,950 ohm centre-tapped primary to a single 8 ohm secondary. Typical DC resistance is 97.36 ohms on both the red-brown and red-blue primary halves and 0.409 ohm on the black-green secondary. At 1.0 kHz, 1.0 V open circuit, primary inductance is 3.99 H (24.8K ohm) and secondary inductance 8.71 mH (66.28 ohm), with 7.03 mH primary leakage inductance.

The drawing gives a frequency response of 70 Hz to 15 kHz (0/-1.5 dB reference @ 1 kHz) and distortion of less than 3% at 70 Hz. It is paper wound, and the materials and design specifications were kept as close as possible to the original part to preserve the stock tone.

Unlike most units in the 1750 series, the 1750F uses 7 in minimum leads. The primary leads are brown, red (centre tap) and blue; the secondary is green common and black 8 ohm. Drawing dimensions are A 3.250 in, B 1.687 in, C 1.995 in and D 2.813 in. It is rated 1500 VRMS and -40 to 105 degC, is RoHS and REACH compliant, and ships at 0.9 lbs (0.41 kg).