Hammond 1750Q 50W JTM 45 Output Transformer, 4/8/16 Ohm

The 1750Q is a 50 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 JTM 45 (P-TM450). Model names are listed by the manufacturer for reference only, and it states it is not affiliated with the amplifier companies. It suits technicians restoring or servicing JTM 45-style circuits.

It has a 7,371 ohm centre-tapped primary, with white and red outer leads and a black centre tap, and secondary taps of 4 ohm (yellow), 8 ohm (green) and 16 ohm (grey) referenced to an orange common. Typical DC resistance is 41.74 ohms white-black and 43.14 ohms black-red on the primary, and 0.580 ohm orange-grey on the secondary.

At 1.0 kHz, 1.0 V open circuit, the white-red primary measures 38.0 H (250K ohm), with 19.87 mH primary leakage inductance. Frequency response is 70 Hz to 15 kHz (0/-1 dB reference @ 1 kHz) and distortion is under 1% at 70 Hz. The bobbin-wound unit was built with materials and design specifications kept as close as possible to the original to preserve the stock tone.

Open-style construction provides long 15 in minimum leads. Drawing dimensions are A 3.125 in, B 3.280 in, C 3.750 in, D 2.500 in and E 2.438 in, with G 0.188 x 0.406 in. Ratings are 2500 VRMS dielectric strength and -40 to 105 degC. The 1750Q is RoHS and REACH compliant and ships at 4 lbs (1.81 kg).