1750JA Hammond PP Übertrager Hot Rod Deluxe 050438 Fender

Hammond 1750JA – 40 W output transformer for Hot Rod and Blues Deluxe

The Hammond 1750JA is a paper-wound push-pull output transformer with a 4.25 kΩ plate-to-plate primary and 4 and 8 Ω secondary taps. Hammond documents it for the Hot Rod Deluxe and Blues Deluxe.

Hammond prints the references as 50438 and 47269. The BTB formats 050438 and 047269 add a leading zero and can also be used when identifying the service part.

Suitable applications

• Fender Hot Rod Deluxe using reference 050438 or 50438
• Fender Blues Deluxe using reference 047269 or 47269
• Push-pull stages using two 6L6 valves and approximately 4.25 kΩ
• Guitar amplifiers with a 4 Ω total loudspeaker load
• Guitar amplifiers with an 8 Ω total loudspeaker load
• New amplifiers in the 40 W transformer class with a suitable load line

Technical data

Product type

Push-pull guitar-amplifier output transformer

Model

Hammond 1750JA

Documented amplifier families

Hot Rod Deluxe and Blues Deluxe

Documented references

50438 and 47269; BTB formats 050438 and 047269

Primary impedance

4.25 kΩ plate-to-plate with centre tap

Secondary impedances

4 and 8 Ω

Transformer power rating

40 W

Amplifier topology

Push pull

Typical output-valve complement

Two 6L6 valves in total at a suitable operating point

Winding type

Paper winding

Primary inductance

Approx. 11.4 H at 1 kHz, 1 V and open secondary

Secondary inductance at the 4 Ω tap

Approx. 28.86 mH

Secondary inductance at the 8 Ω tap

Approx. 55.60 mH

Brown-to-red primary DC resistance

Approx. 82.0 Ω

Red-to-blue primary DC resistance

Approx. 108.3 Ω

Total primary DC resistance

Approximately 190.3 Ω

Secondary DC resistance at the 4 Ω tap

Approx. 0.253 Ω

Secondary DC resistance at the 8 Ω tap

Approx. 0.462 Ω

Primary leakage inductance

Approx. 31.39 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 279 mm or 11 inches

Dimensions

Approx. 63.5 × 80.0 × 82.7 mm

Mounting dimensions

Approx. 50.8, 54.6 and 67.3 mm according to the manufacturer drawing

Mounting slots

Approx. 4.8 × 9.5 mm

Hammond shipping weight

Approx. 1.36 kg

Manufacturing note

Made in Canada according to the current component drawing

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

Green/yellow

4 Ω loudspeaker tap

Green

8 Ω loudspeaker tap

Selecting the loudspeaker tap

The selected secondary tap must match the total impedance of all connected loudspeakers. Calculate the resulting impedance where speakers are connected in series, parallel or series-parallel.

Insulate the unused secondary lead. The 4 and 8 Ω taps are not intended to operate simultaneously as two independently loaded loudspeaker outputs.

Reference and amplifier version

The reference number provides a more reliable service identifier than the model name alone. Verify the PCB or chassis version, speaker load, mounting, lead colours and feedback phase before replacement.

Safety notes

Lethal voltage is present on the primary circuit. Install the open 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 Deluxe 050438 or Blues Deluxe 047269?

Hammond 1750JA is intended for these applications, documented as 50438 and 47269, and provides 4.25 kΩ plate-to-plate, 4/8 Ω taps, paper winding and a 40 W rating.

Which 40 W push-pull output transformer suits two 6L6 valves with a choice of 4 or 8 Ω?

Hammond 1750JA is a suitable starting point for a correctly designed two-6L6 stage requiring approximately 4.25 kΩ plate-to-plate and a total loudspeaker load of 4 or 8 Ω.

Can the Hammond 1750JA be configured for either 4 or 8 Ω?

Yes, the Hammond 1750JA has separate 4 and 8 Ω secondary taps. Use only the tap that corresponds to the actual total loudspeaker impedance.

Can the Hammond 1750JA be used in a newly designed 6L6 push-pull amplifier?

Yes, the Hammond 1750JA can be used in a new amplifier when the 4.25 kΩ load, 40 W rating, speaker impedance, valve count, plate and screen voltage and quiescent currents correspond to the circuit.