1750T Hammond PP Übertrager AC30 Reissue Vox 4k 8/16

Hammond 1750T – AC30 Reissue output transformer with 4 kΩ and bobbin winding

The Hammond 1750T is a bobbin-wound push-pull output transformer for the Vox AC30 Reissue. It provides 4 kΩ plate-to-plate, a 30 W rating and separate 8 and 16 Ω secondary taps.

Hammond lists P-TVO30R as the comparison reference. Its long leads and documented Reissue assignment distinguish the 1750T from the paper-wound 1750V Vintage version.

Suitable applications

• Vox AC30 Reissue amplifiers with a matching transformer and chassis version
• Replacement applications around comparison reference P-TVO30R
• Push-pull stages using four EL84 or 6BQ5 valves in total
• New amplifiers requiring approximately 4 kΩ in the 30 W transformer class
• Total loudspeaker loads of 8 or 16 Ω
• AC30 service projects requiring particularly long flying leads

Technical data

Product type

Push-pull guitar-amplifier output transformer

Model

Hammond 1750T

Documented amplifier application

Vox AC30 Reissue

Hammond comparison reference

P-TVO30R

Primary impedance

4 kΩ plate-to-plate with centre tap

Secondary impedances

8 and 16 Ω

Transformer power rating

30 W

Typical output-valve complement

Four EL84 or 6BQ5 valves in total

Winding type

Bobbin winding

Primary inductance

Approx. 15.2 H at 1 kHz, 1 V and open secondary

Red-to-brown primary DC resistance

Approx. 54.00 Ω

Brown-to-white primary DC resistance

Approx. 60.00 Ω

Total red-to-white primary DC resistance

Approximately 114.00 Ω

Black-to-blue secondary DC resistance

Approx. 0.520 Ω across the complete 16 Ω winding

Secondary inductance at 8 Ω

Approx. 37.45 mH

Secondary inductance at 16 Ω

Approx. 70.66 mH

Primary leakage inductance

Approx. 4.61 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 533 mm or 21 inches

Dimensions

Approx. 79.4 × 83.8 × 96.5 mm

Mounting dimensions

Approx. 63.5 × 61.9 mm

Mounting slots

Approx. 4.8 × 10.3 mm

Hammond shipping weight

Approx. 1.81 kg

Manufacturing note

Made in Canada according to the current component drawing

Lead connections

Red

First primary connection to one output-valve group

Brown

Primary centre tap to B+

White

Second primary connection to the opposite output-valve group

Black

Secondary common or loudspeaker ground

Green

8 Ω loudspeaker tap

Blue

16 Ω loudspeaker tap

Selecting the loudspeaker impedance

Use the green lead for an 8 Ω total load and the blue lead for 16 Ω. Insulate the unused secondary tap separately.

No 4 Ω tap is provided. An intentional mismatch changes the primary load reflected to the four EL84 valves and requires a new operating-point assessment.

Comparison with the Hammond 1750V

Hammond 1750T

Bobbin winding, AC30 Reissue, P-TVO30R and at least 21-inch flying leads

Hammond 1750V

Paper winding, AC30 Vintage, P-TVO30V and different winding and mechanical data

Both models are nominally rated at 4 kΩ, 8/16 Ω and 30 W, but their different construction means that they should not be treated as automatically interchangeable.

Safety notes

Lethal plate and signal voltages are present on the primary. Install the transformer with complete touch protection and verify feedback phase after replacement.

Questions about selection and use

Which output transformer suits a Vox AC30 Reissue using P-TVO30R?

Hammond 1750T is documented for the Vox AC30 Reissue and comparison reference P-TVO30R and provides 4 kΩ plate-to-plate, 8/16 Ω taps, bobbin winding and a 30 W rating.

Which 30 W output transformer suits four EL84 valves requiring 4 kΩ plate-to-plate?

Hammond 1750T is a suitable starting point for a correctly designed four-EL84 push-pull stage requiring 4 kΩ plate-to-plate and a total loudspeaker load of 8 or 16 Ω.

Can the Hammond 1750T be configured for 8 or 16 Ω?

Yes, the Hammond 1750T has a green 8 Ω tap and a blue 16 Ω tap. Use the connection matching the actual total loudspeaker impedance.

Is the Hammond 1750T suitable for an AC30 Reissue repair?

Yes, the Hammond 1750T is suitable for an AC30 Reissue repair when P-TVO30R, the 4 kΩ load, mounting, lead routing and 8 or 16 Ω output correspond to the particular amplifier.