Vox Continental repeat percussion circuit

Late 1964 on

In progress February 2026

A preliminary note on JMI's repeat percussion circuit (OS/063). There were at least two versions, one early (December 1964), and one late (December 1965 with further additions/changes).

The information panel of OS/063, December 1964.

The later (adjusted) sheet was evidently intended not only for use in the Continental, but the Guitar Organ and Electronic Accordion too.

Guitar Organ, 1966. The percussion circuit occupies around two thirds of the upper section.

JMI schema.

One of the key characteristics of the two JMI circuits as we have them (early and late) is the use of a pair of interstage transformers (T1 and T2 in the schema above). It may be no coincidence that one finds the same arrangement in an early circuit employed and probably devised by Thomas Organ. Below, a thumbnail of the sheet for the Thomas BL-3 (also known as the "Coronado"). The BL-3 was one of the models displayed by Jennings for Thomas at the Russell Hotel Trade Fair in August 1964.

Thomas Organ model BL-3. One finds the same divisions on the JMI sheets - Trigger, Multivibrator, Modulator.

Jennings advert for Thomas, August 1964. Jennings had been appointed the main UK distributor by Thomas in the summer of 1963 and remained so until January 1967.

Thomas also employed the circuit in its BL-1, VL-3, VL-3A, and O organs, the BL-3 and VL-5 being precursors of the BL-3 and VL-5 shown in London.

Thomas "Electronic Organ Service Manual", vol. 2, notes, bulletins, and circuit diagrams for eighteen models from the first years of the 1960s.

Thomas later revised the circuit, omitting the transformers, so some care (in terms of reference) is needed. Note that the sheet pictured above (for the BL-3), part of a large collection of material given away by Thomas when it closed its offices and service centre in West London (Alperton), is "Schematic No. 2". "Schematic No. 1" covers filtering, voicing, and so on.

The very earliest Thomas circuits (late 1950s, 1960, and 1961), are based around a pulsing neon lamp.

As has been mentioned before, the other avenue for investigation goes back much further - the transistorised effects module created by JMI for its D2 Entertainment organ.

October 1959.

The Thomas connection seems the more promising at the moment, however.