1750KA Hammond PP Übertrager Bassman 59 036485 Fender

Hammond 1750KA – 50 W output transformer for ’59 Bassman and Vibro-King

The Hammond 1750KA is a paper-wound push-pull output transformer with a 4.15 kΩ plate-to-plate primary and a fixed 2 Ω loudspeaker output. Hammond documents it for the Bassman 59 Reissue, Concert and Vibro-King.

Hammond prints the reference as 36485, while BTB uses the six-digit 036485 format. The current Hammond list also assigns references 125A9A and 022855 to additional applications.

Suitable applications

• Fender Bassman 59 Reissue using reference 036485 or 36485
• Documented Fender Vibro-King output stages
• Documented Concert, Brownface and Blackface applications
• Push-pull output stages requiring approximately 4.15 kΩ
• Correctly designed two-6L6 or 5881 output stages
• Multiple-speaker systems with a total impedance of 2 Ω

Technical data

Product type

Push-pull guitar-amplifier output transformer

Model

Hammond 1750KA

Documented amplifier families

Bassman 59 Reissue, Concert and Vibro-King

Documented references

36485, 125A9A and 022855; BTB format 036485

Documented chassis families

Including 6G12, 6G12A, AA763, Brownface and Blackface

Primary impedance

4.15 kΩ plate-to-plate with centre tap

Secondary impedance

2 Ω

Transformer power rating

50 W

Amplifier topology

Push pull

Typical output-valve complement

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

Winding type

Paper winding

Primary inductance

Approx. 11.3 H at 1 kHz, 1 V and open secondary

Secondary inductance

Approx. 4.20 mH at 1 kHz, 1 V and open primary

Brown-to-red primary DC resistance

Approx. 45.53 Ω

Red-to-blue primary DC resistance

Approx. 49.09 Ω

Total primary DC resistance

Approximately 94.62 Ω

Secondary DC resistance

Approx. 0.140 Ω

Primary leakage inductance

Approx. 5.16 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 305 mm or 12 inches

Dimensions

Approx. 102.9 × 83.3 × 88.9 mm

Mounting dimensions

Approx. 88.9 × 52.1 × 65.3 mm according to the manufacturer drawing

Mounting slots

Approx. 4.75 × 7.62 mm

Hammond shipping weight

Approx. 2.27 kg

Manufacturing note

Made in Canada according to the current component drawing

Lead connections

Blue

First primary connection to one output-valve plate

Red

Primary centre tap to B+

Brown

Second primary connection to the opposite output-valve plate

Black

Secondary common or loudspeaker ground

Green

2 Ω loudspeaker connection

Phase

Follow the particular amplifier circuit exactly where feedback is used

Total load with multiple speakers

The fixed 2 Ω output is intended for a speaker combination providing approximately 2 Ω in total. Consider the impedance of every speaker together with its series or parallel connection.

Before replacement in a Vibro-King, Concert or Bassman, verify the circuit revision, mounting dimensions, lead colours and feedback phase. The reference is a strong identifier but does not replace these checks.

Comparison with the Hammond 1750K

The Hammond 1750KA uses 4.15 kΩ plate-to-plate and is explicitly documented for 36485 applications including the Bassman 59 Reissue. The Hammond 1750K instead uses 4 kΩ and is primarily listed with references 125A9A and 022855.

Both models have a fixed 2 Ω output and a 50 W rating, but their different primary data, mechanics and equipment assignments mean that they should not be treated as identical solely on that basis.

Safety notes

Lethal plate voltage is present on the primary. Install the approximately 2.27 kg transformer with complete touch protection and adequate chassis reinforcement.

Questions about selection and use

Which output transformer suits a ’59 Bassman Reissue using reference 036485?

Hammond 1750KA is documented for the Bassman 59 Reissue with the reference printed by Hammond as 36485 and provides 4.15 kΩ plate-to-plate, a fixed 2 Ω output and a 50 W rating.

Which 50 W push-pull output transformer provides 4.15 kΩ plate-to-plate to 2 Ω for Vibro-King or Concert applications?

Hammond 1750KA is intended for these documented Fender application families and combines a 4.15 kΩ primary, paper winding and a fixed 2 Ω secondary.

Can the Hammond 1750KA be used in a newly designed two-6L6 or 5881 amplifier?

Yes, the Hammond 1750KA can be used in a new amplifier when the 4.15 kΩ load, 2 Ω output, 50 W rating, valve count, plate and screen voltage and quiescent currents suit the circuit.

Can the Hammond 1750KA operate with a multiple-speaker load totalling 2 Ω?

Yes, the Hammond 1750KA can operate with a correctly calculated total load of 2 Ω. Verify the impedances and connection of every individual speaker first.