Below, an overview of the printed circuit boards developed by JMI for the Vox Continental single manual organ, mid 1964 to early 1968, and a provisional list of the numbers assigned to them. It should be possible to fill the various gaps in the list (as it stands at present) in due course. Known component layout diagrams are listed on this page.

For the sake of convenience, the "typology" devised by the Thomas Organ Company for its pocket service manual for dealers (late 1966) has been adopted. JMI began exporting large numbers of organs (and amplifiers, etc.) to Thomas in September 1964, the "Million Dollar Deal" being in actual fact a series of "deals" and orders running through to mid 1966.

Organs assembled at Dartford Road and the West Street Works at Erith had serial numbers with the prefix "TC" (Transistor Continental); those contracted out to Burndept Electronics for assembly had "BD".

So far as one can tell, serial numbers for Burndept-made organs, beginning at 3000, may have been assigned well before West-Street-made organs had reached the end of the 2000s. Burndept stuck to its mode of assembly for the whole of its production run. Changes introduced by JMI in the 2600s (insofar as serial numbers are concerned) were not adopted.

JMI Type I

Type I boards are not printed circuit boards at all. They are through-hole solder boards, as the example below shows. As early Continentals were not exported to the USA in any great number, Thomas did not expect many enquiries from its dealers.

Board in an early Continental, component legs soldered. not a printed circuit board.

JMI PCB Type II

Continental serial numbers TC 1300s - 1760

At this stage, generator / divider boards only. Other boards are of the traditional solder tag variety.

Thomas pocket service manual for dealers.

TC 1618.

Boards are mounted at an angle in a metal enclosure. An easy way to identify this "type" - if a loose board turns up for instance - is by the presence of the inductor at the corner.

JMI PCB Type III

Continental serial numbers TC 1763 to TC 2900s; BD 3000 to 3900s; TC 4000 to 4300

This type of board corresponds with JMI component layout drawing TO/049, dated November 1965, the innovation at this point being edge connectors (pins).

Thomas pocket service manual for dealers.

JMI component layout sheet TO/049, dated November 1965.

TC 1888.

TC 2963. The same board as above, but different makes of component.

Different types of components are used at various points through to the end of production by JMI.

PCBs for the Preamp and Vibrato boards

Continental serial numbers TC 2673 to 3000; TC 4000 to 4300

It should be noted that these boards were not encompassed in the Thomas Organ reference manuals. Thomas had begun producing its own version of the Continental at this point, in parallel with imports from Italy (which were different again).

Note that organs assembled by Burndept - serial numbers c. BD 3000 to BD 3900s - generally did not have these boards.

Vibrato board. JMI component layout sheet TO/050, dated September 1965.

Preamp board. JMI component layout sheet TO/052, dated October 1965.

TC 2933, Preamp board in this view above the Vibrato board, some capacitors replaced, but the two conform with the schemas on the JMI sheets.

JMI printed circuit board part numbers

JMI 46 - Generator / Divider board (component layout diagram TO/049, drawn Nov. 1965).

JMI 47 - Vibrato board (component layout TO/050, drawn Sept. 1965).

JMI 48 - Preamp board (component layout TO/052, drawn Oct. 1965).

JMI 49 - Repeat Percussion board (revised version, 1965/1966), circuit published in "Electronic Organ Magazine", April 1969.

JMI 50 - currently unknown.

JMI 51 - Guitar Organ, Generator / Divider board.

JMI 52A-52E - Guitar Organ, voicing circuits.

JMI 53S - Vibrato Board, a revised version later 1966 (?), circuit published in "Electronic Organ Magazine", April 1969.

JMI 54 to JMI 59 - currently unknown.

JMI 60 - Guitar Organ, mother board.

Below, the notes on JMI 53S - a revised Vibrato circuit board - published in "Electronic Organ Magazine", April 1969. The standard Vibrato board was JMI 47.

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