1750M Hammond PP Übertrager Fender 125A13A 022871

Hammond 1750M – 60 W output transformer with 2, 4 and 8 Ω taps

The Hammond 1750M is a push-pull output transformer providing 4.2 kΩ plate-to-plate and secondary taps for 2, 4 and 8 Ω. Hammond documents it for several Hot Rod DeVille, Concert II and Super Concert versions.

Its flexible secondary supports several loudspeaker configurations without changing the nominal primary load. The amplifier version, reference and mechanical layout still require complete verification before replacement.

Suitable applications

• Fender Hot Rod DeVille amplifiers with a matching transformer reference
• Concert II and Super Concert 93 amplifiers with a corresponding chassis version
• Replacement applications involving 125A13A, 022871 or 041754
• Push-pull stages using two 6L6, 5881 or compatible power valves
• Loudspeaker configurations totalling 2, 4 or 8 Ω
• New amplifiers requiring approximately 4.2 kΩ in the 60 W transformer class

Technical data

Product type

Push-pull guitar-amplifier output transformer

Model

Hammond 1750M

Documented amplifier families

Hot Rod DeVille, Concert II and Super Concert 93

Documented or assigned references

125A13A, 022871 and 041754 or 41754

Primary impedance

4.2 kΩ plate-to-plate with centre tap

Secondary impedances

2, 4 and 8 Ω

Transformer power rating

60 W on the current product page and series list; the component drawing carries a 50/60 W marking

Amplifier topology

Push pull

Typical output-valve complement

Two 6L6, 6L6GC or 5881 valves in total at a suitable operating point

Winding type

The current product and application pages state paper winding, while the general Hammond series list states bobbin

Primary inductance

Approx. 5.60 H at 1 kHz, 1 V and open secondary

Secondary inductance at the 2 Ω tap

Approx. 8.53 mH

Secondary inductance at the 4 Ω tap

Approx. 17.08 mH

Secondary inductance at the 8 Ω tap

Approx. 32.63 mH

Primary DC resistance

Approx. 68.0 Ω between brown and blue

Secondary DC resistance at the 2 Ω tap

Approx. 0.235 Ω

Secondary DC resistance at the 4 Ω tap

Approx. 0.302 Ω

Secondary DC resistance at the 8 Ω tap

Approx. 0.355 Ω

Primary leakage inductance

Approx. 8.03 mH at 1 kHz, 1 V and short-circuited secondary

Frequency response

70 Hz to 15 kHz, 0/-1 dB referenced to 1 kHz

Distortion

Less than 1% at 70 Hz under the documented test conditions

Dielectric test

2,000 V RMS

Temperature range

-40 to +105 °C

Lead length

At least approximately 229 mm or 9 inches

Dimensions

Approx. 102.9 × 81.8 × 88.9 mm

Mounting dimensions

Approx. 88.9 × 50.8 mm

Mounting slots

Approx. 4.75 × 7.62 mm

Hammond shipping weight

Approx. 1.81 kg

Lead connections

Brown

First primary connection to one output-valve plate

Red

Primary centre tap to B+

Blue

Second primary connection to the opposite output-valve plate

Black

Secondary common or loudspeaker ground

White

2 Ω loudspeaker tap

Green/yellow

4 Ω loudspeaker tap

Green

8 Ω loudspeaker tap

Selecting the secondary tap

Use only the tap corresponding to the complete impedance of all connected loudspeakers. Calculate the final load where multiple speakers use series, parallel or series-parallel wiring.

Insulate every unused secondary lead separately. The taps are not three independently loadable loudspeaker outputs for simultaneous use.

Comparison with the Hammond 1750L

The Hammond 1750L has a fixed 4 Ω output and an unambiguous paper-winding specification. The Hammond 1750M adds 2 and 8 Ω taps but currently has conflicting official winding-type information.

An original-style repair must therefore check not only the 4.2 kΩ and 60 W ratings but also mounting, lead routing, secondary taps and the actual delivered construction.

Safety notes

Lethal plate voltage is present on the primary. Install the transformer with complete touch protection and fully discharge the amplifier before service work.

Questions about selection and use

Which output transformer suits a Hot Rod DeVille or Super Concert requiring 4.2 kΩ and 2, 4 or 8 Ω?

Hammond 1750M is intended for documented Hot Rod DeVille and Super Concert applications and provides 4.2 kΩ plate-to-plate, 2/4/8 Ω taps and a 60 W rating.

Which Hammond output transformer covers references 125A13A, 022871 and 041754?

Hammond 1750M is assigned to these reference families on current Hammond application and selection lists; the chassis version, mounting and secondary wiring must correspond before installation.

Can the Hammond 1750M be configured for 2, 4 or 8 Ω?

Yes, the Hammond 1750M has separate secondary taps for 2, 4 and 8 Ω. Use the tap matching the actual total loudspeaker impedance.

Is the Hammond 1750L a suitable alternative for a fixed 4 Ω load?

Yes, the Hammond 1750L can be a technically suitable alternative in a documented 4 Ω application when the reference, mechanics, 4.2 kΩ primary load and feedback phase correspond to the amplifier.