1750P Hammond PP Übertrager JCM900 JCM2000 50W Marshall

Hammond 1750P – pin-mounted 50 W output transformer for Marshall JCM900

The Hammond 1750P is a pin-mounted push-pull output transformer providing 3.4 kΩ plate-to-plate and secondary connections for 4, 8 and 16 Ω. The current Hammond selection list assigns it to 50 W Marshall JCM900 amplifiers.

The output-valve complement can vary by JCM900 version and market. Primary load, pin layout, chassis revision and loudspeaker connections are therefore more reliable selection criteria than a universal valve designation.

Suitable applications

• Marshall JCM900 amplifiers in a compatible 50 W version
• Service replacement with a matching pin and mounting layout
• Push-pull stages requiring approximately 3.4 kΩ
• Total loudspeaker loads of 4, 8 or 16 Ω
• Equipment using a chassis- or pin-mounted output transformer
• New amplifiers in the 50 W transformer class following complete circuit verification

Technical data

Product type

Pin-mounted push-pull guitar-amplifier output transformer

Model

Hammond 1750P

Documented amplifier family

Marshall JCM900, 50 W versions

Primary impedance

3.4 kΩ plate-to-plate with centre tap

Secondary impedances

4, 8 and 16 Ω

Unsupported BTB or product-page figure

No reliably documented 2 Ω tap

Transformer power rating

50 W

Amplifier topology

Push pull

Output-valve complement

Version-dependent; determine it from the exact JCM900 circuit

Winding type

Bobbin winding

Primary inductance

Approx. 22.65 H at 60 Hz, 10 V and open secondary

Primary DC resistance from pin 4 to pin 2

Approx. 40.70 Ω

Primary DC resistance from pin 2 to pin 7

Approx. 41.47 Ω

Total primary DC resistance from pin 4 to pin 7

Approx. 82.25 Ω

Secondary DC resistance at 4 Ω

Approx. 0.351 Ω between pins 23 and 21

Secondary DC resistance at 8 Ω

Approx. 0.506 Ω between pins 23 and 16

Secondary DC resistance at 16 Ω

Approx. 0.725 Ω between pins 23 and 14

Primary leakage inductance

Approx. 10.30 mH at 60 Hz, 10 V and short-circuited secondary

Frequency response

50 Hz to 12 kHz, 0/-1 dB referenced to 1 kHz

Distortion

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

Dielectric test

2,250 V RMS

Temperature range

-40 to +105 °C

Connection type

Pin-mounted chassis construction

Dimensions

Approx. 95.5 × 78.5 × 79.5 mm

Mounting dimensions

Approx. 63.5 × 79.5 mm according to the manufacturer drawing

Hammond shipping weight

Approx. 1.81 kg

Pin connections

Pin 7

First primary connection to one output-valve plate or plate group

Pin 2

Primary centre tap to B+

Pin 4

Second primary connection to the opposite plate or plate group

Pin 23

Secondary common

Pin 21

4 Ω loudspeaker connection

Pin 16

8 Ω loudspeaker connection

Pin 14

16 Ω loudspeaker connection

View

Compare every pin number with the underside view in the manufacturer drawing before installation

Difference from JCM2000 and the Hammond 1750N

The current Hammond series list and dedicated application page assign the 1750P to the JCM900. No current primary-source confirmation was found for a JCM2000 application.

The Hammond 1750N provides 3.2 kΩ, flying leads and a JMP/JCM800 assignment. The 1750P provides 3.4 kΩ, pin terminals and a JCM900 assignment, so the two models are not equivalent merely because both are rated at 50 W.

Selecting the loudspeaker connection

The 4, 8 or 16 Ω pin must match the total impedance of the connected loudspeakers. The remaining secondary terminals stay unloaded.

Safety notes

Lethal plate and signal voltages are present on the primary pins. Pin spacing, insulation and chassis mounting require qualified implementation.

Questions about selection and use

Which output transformer suits a compatible 50 W Marshall JCM900?

Hammond 1750P is assigned to the 50 W JCM900 in the current Hammond selection list and provides 3.4 kΩ plate-to-plate with 4/8/16 Ω connections.

Which pin-mounted 50 W output transformer provides 3.4 kΩ and three speaker impedances?

Hammond 1750P combines a pin-mounted construction with a 3.4 kΩ plate-to-plate primary and separate secondary connections for 4, 8 and 16 Ω.

Can the Hammond 1750P be configured for 4, 8 or 16 Ω?

Yes, the Hammond 1750P has dedicated pins for 4, 8 and 16 Ω. Use the connection matching the actual total loudspeaker impedance.

Is the Hammond 1750P suitable for different JCM900 revisions?

Yes, the Hammond 1750P can be used in a compatible JCM900 revision when the 3.4 kΩ load, 50 W rating, pin layout, mounting, loudspeaker load and output-stage circuit correspond.