1750A Transformer for Tube Guitar Amps

Reverb Driver

• Designed for drop-in replacement of original units.
• Physically, parts were designed to look similar to original factory units (where possible).
• Materials used & design specs. were kept as close as possible to the original part to preserve the stock "tone".
• Output transformers marked UPGRADE (below) allow for more versatility by added secondary connections that did not exist on the original units.
• The Hammond 1750A is a 3.5-watt, single-ended output transformer specifically designed as a drop-in replacement part to suit the spring reverb driver circuit found in a wide variety of classic Fender tube amplifiers.
  It is equivalent to original Fender OEM part numbers 125A20B and 022921

It is a single-ended ~3.5 W reverb driver (typically ~22.8–25 kΩ primary to 8 Ω secondary) used with a 12AT7 driver tube and a transformer-driven spring reverb tank (commonly Accutronics-style 4AB3C1B or similar).

Common Fender amps that use it

It was the standard reverb driver across most Fender tube amps with onboard spring reverb from roughly the mid-1960s through the 1980s/early 1990s (blackface, silverface, and many later production/reissue models). Confirmed or widely documented models include:

• Princeton Reverb (and reissues such as ’65 Princeton Reverb)
• Deluxe Reverb (and reissues such as ’65 Deluxe Reverb, ’64 Custom Deluxe Reverb)
• Vibrolux Reverb
• Pro Reverb
• Super Reverb (and reissues)
• Twin Reverb (and reissues such as ’65 Twin Reverb)
• Quad Reverb
• Super Six Reverb
• Vibrosonic / Vibrosonic Reverb
• Bandmaster Reverb
• Vibroverb (certain models / reissues; note 037099 is sometimes referenced for the ’63 Vibroverb Reissue)
• Prosonic
• Various other blackface/silverface and reissue models with the classic 12AT7 + transformer-driven reverb circuit

It is also referenced for some non-Fender uses (e.g., certain Mesa Boogie circuits).

Notes:

• Not every Fender amp with “Reverb” in the name uses this exact transformer (e.g., some standalone reverb units or later solid-state/digital designs differ). Always verify the specific chassis/schematic or the original part number stamped on the transformer if possible.
• Hammond lists the 1750A simply as “Reverb Driver” matching 125A20B & 022921.

This is the common “workhorse” Fender reverb driver transformer used in the vast majority of classic tube reverb circuits from that era.

Not what you're looking for? See this table for further help.