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Hammond • Reverb • Guitar Amp Parts

Hammond Type IV Reverb Tank
AO-23580-11 – Tested & Working

This is a real Hammond Organ Company Type IV spring reverberation unit, part number AO-23580-11. It still has the original silver and blue factory label that reads “REVERBERATION UNIT TYPE IV – HAMMOND ORGAN COMPANY – CHICAGO, ILL.”

I pulled this tank from a working L-100 series organ and bench-tested it. The two long springs are straight, under good tension, and produce the classic lush spring decay these units are known for. RCA input and output jacks are present and labeled. Original mounting brackets and the white rubber isolation grommets are included.

The silver chassis is clean with only light dust and minor age marks — no heavy rust or damage. This is a solid, ready-to-use tank for a guitar amp build, DIY reverb unit, or Hammond restoration.

Important packing note: The springs will be immobilized with a soft foam insert for shipping. Please remove the foam carefully before installing the tank.