Hammond 1750PA 18W Marshall Combo Output Transformer, 4/8/16 Ohm

The 1750PA is an 18 watt push-pull output transformer for tube guitar amplifiers, designed as a drop-in replacement for original units such as the one in the Marshall 18-Watt Combo. Model names are listed by the manufacturer for reference only, and it states that it is not affiliated with the amplifier companies.

It provides an 8,400 ohm centre-tapped primary (blue-red-brown) and three secondary taps from a black common: yellow 4 ohm, green 8 ohm and orange 16 ohm. Typical DC resistance is 298.94 ohms brown-red and 335.45 ohms red-blue on the primary and 1.40 ohm black-orange on the secondary. At 1.0 kHz, 1.0 V open circuit, the primary measures 70.30 H (430K ohm); primary leakage inductance is 66.18 mH.

The drawing lists a frequency response of 70 Hz to 15 kHz (0/-2 dB reference @ 1 kHz) and distortion under 1% at 70 Hz. The paper-wound unit was built with materials and design specifications kept as close as possible to the original part to preserve the stock tone, and constructed to look similar to the factory original where possible.

Open-style construction gives 7 in minimum leads. The drawing shows dimensions of 4.0003 in, 3.5615 in, 2.6255 in and 2.0411 in, with a 0.1870 in diameter hole, and the unit label is marked Made in Canada. Ratings are 1500 VRMS and -40 to 105 degC. The 1750PA is RoHS and REACH compliant and ships at 4 lbs (1.81 kg).