Hammond 1750M 60W Hot Rod Deville Output Transformer, 2/4/8 Ohm

The 1750M is a push-pull output transformer for tube guitar amplifiers, rated 60 W on the part page (the drawing marks it 50/60 W). It is designed as a drop-in replacement for the original unit in the Fender Super Concert 93 and Hot Rod Deville, and is listed as similar to Fender part number 41754.

A 4,200 ohm centre-tapped primary feeds three secondary taps: 2 ohm (white), 4 ohm (green/yellow) and 8 ohm (green), all referenced to a black common. Typical DC resistance is 68.0 ohms brown-blue on the primary, and 0.235, 0.302 and 0.355 ohm on the black-white, black-green/yellow and black-green secondaries. At 1.0 kHz, 1.0 V open circuit, the primary measures 5.60 H (35.6 KOhm), with secondary inductances of 8.53 mH (88.34 ohm), 17.08 mH (154.20 ohm) and 32.63 mH (275.10 ohm). Primary leakage inductance is 8.03 mH.

The drawing gives a frequency response of 70 Hz to 15 kHz (0/-1 dB reference @ 1 kHz) and distortion under 1% at 70 Hz. Materials and design specifications were kept as close as possible to the original part to preserve the stock tone. Note that the part page lists a paper winding while the series ordering table lists bobbin.

The open-style unit has 9.0 in minimum leads, with blue and brown primary leads and a red centre tap. Drawing dimensions are A 4.050 in, B 3.220 in, C 3.500 in, D 3.500 in, E 2.000 in and F 2.510 in, with G 0.187 x 0.300 in. Ratings are 2000 VRMS and -40 to 105 degC. The 1750M is RoHS and REACH compliant and ships at 4 lbs (1.81 kg).