The main index page on Vox Continentals can be found here. New material is currently in preparation (March 2024) - to be signalled when ready on the main site updates page.

"OS" sheets for the Continental - circuit diagrams

Dates are given in standard British format.

The "OS" series encompassed circuit diagrams of all sorts - amplifiers, echo units, transistor organs (principally though not exclusively the single manual Continental), the guitar organ, and so on, running from early 1958 through to early 1968. OS/209, for a solid state PA amplifier, is the latest JMI sheet currently known.

OS/027a: Dividers. Drawn 19/2/63. Addition of 21/2/63. Referenced in OS/064. Copy in the Thomas Organ service manual, 1967.

OS/027b: Dividers. Redrawn 6/6/66.

OS/028: Power supply and Vibrato. Drawn 28/2/63. Additions through to 25/9/64. Referenced in OS/064. Copy in the Thomas Organ service manual, 1967.

OS/029: Layout board for Vibrato. Drawn 7/3/63. Copy in the Thomas Organ service manual, 1967.

OS/030: Drawbars and Filters. Drawn 2/4/63. Referenced in OS/064. Copy in the Thomas Organ service manual, 1967.

O0S/036: Drawbars and Filters. Drawn 2/4/63.

OS/063a: Continental Organ Repeat Percusssion. 7/12/64. Referenced in OS/064.

OS/063b: Continental and Guitar Organ Repeat Percussion. Additions through to 1966. Copy in the Thomas Organ service, 1967.

OS/064: Block diagram for the single manual. Drawn 20/11/64, updated 11/2/65. Copy in the Thomas Organ service data for the Guitar Organ, 1967.

OS/077: Five octave generator. Drawn 25/1/65.

OS/095: Double Manual Continental, Walking Bass. Drawn 17/1/65.

OS/124: Vibrato Board circuit. Drawn 27/4/66.

OS/125: Preamp. Drawn 27/4/66.

A number of the diagrams listed above were redrawn in Italy (Recanati) by EKO in late 1965 and early 1966 when production was farmed out to EME for Thomas Organ.

"TO" series - layout sheets for the Continental

Again, dates are given in standard British format.

TO/036: Inductor values for oscillators. Referenced in OS/027 (1966).

TO/037: Capacitor values for generator octaves. Referenced in OS/027 (1966).

TO/039: Contact assembly. Referenced in OS/064.

TO/040: Isolator assembly. Referenced in OS/064.

TO/042: Isolator assembly. Referenced in OS/064.

TO/045: C/F no. 1. Referenced in OS/064.

TO/046: C/F no. 2. Referenced in OS/064.

TO/049: 7-octave Generator and Divider Board. Colour. Drawn 30/11/65. Makes reference to OS/027. Monochrome copy in the Thomas Organ service manual, 1967.

TO/050: Preamp Board. Colour. Drawn 13/9/65. Referenced in OS/125.

TO/052: Vibrato Board. Colour. Drawn 10/10/65. Referenced in OS/124.

TO/065: Dealers Servicing Diagram. Block Diagram. Drawn 5/7/66. Designed for use with JMI's booklet "Theory of Operation".

The nature and scope of TO/001 to TO/036, and TO/038 is currently unknown. The prefix "TMO" was generally used for sheets specific to the Super Continental (dual manual). With the advent of the Riviera in 1967, the "TO" sequence seems to have come to an end. Layout sheets for the new organ are prefixed "TRA" and "TRC".

Below, simply for general reference for the time being, copies of OS/124 and TO/052, the one referencing the other. The principal draughtsman in late 1965 and early 1966 was R.A. Lester, who appears to have worked exclusively for the Organ Dept, at the West Street Works in Erith. Albert Hogben did more or less everything else at this time.

Lester's office initially will have been on the top floor of the Works, where final assembly of the Continentals took place. After the fire of December 1965, he is likely to have moved back to Dartford Road.

OS/124, drawn on 27th March, 1966, referencing TO/052.

TO/052, dated 10th October 1965. This replaced OS/030 of early 1963.

JMI Service Data folder, early 1966.

The name on the front is that of Ken McDonnell, Jennings Organ Production Manager from early days (at least as far back as 1956). The person who made the notes presumably jotted them down while on the phone to the Service Department at Erith - "McDonnell" is given, at second attempt, as "McDonnall".

The folder contains a number of sheets that are scarce these days - four "TO" layouts (part in colour), and a series of diagrams produced by JMI in early 1965 and early 1966 for the Super Continental (two manual).

Also encompassed is a 10" x 8" booklet issued by JMI on the "Theory of Operation". Pictures of another copy were available on the web some years ago (can't recall where), but those seem to have disappeared.

The folder measures 13" x 8 1/2".

The JMI circuit diagrams and layout sheets contained in the folder.

JMI's "Dealer Servicing Diagram" and "Theory of Operation" booklet

Early 1966

Below a small copy (for the time being) of JMI's "Dealers Servicing Diagram", a fairly detailed "block diagram" for the single manual Continental drawn by R.A. Lester in July 1966, designated TO/065. The sheet measures 15 1/2" x 11 3/4". It was designed for use with the "Theory of Operation" booklet.

TO/065 - block diagram of the single manual Contintental organ for dealers.

TO/065, panel.

The blocks (also referenced in the booklet) are: 6500 = generator boards; 7100 = vibrato; 7200 = preamp; 7300A = power supply; 7400 = keyboard contact assembly. The booklet adds 7700 for the dual manual "walking bass". The dealers servicing diagram for the dual manual Continental will be posted soon.

Front cover and first page of the booklet.

Block diagrams were a standard means at Jennings (as for other organ makers) of giving an overview of the relationship of elements. Below, a sheet drawn by Derek Underdown, c. 1957, for the Jennings Organ Company's "V" series organs.

Block diagram drawn by Derek Underdown for the "V" series organs, c. 1957.

Layout sheet TO/049

Some preliminary notes on JMI layout sheet TO49 for the tone generator board of the Continental organ. The copy illustrated below, dated November 1965, is likely to have been drawn up to accompany the release of the Super Continental dual manual.

The sheet measures 13" x 8". OS/030 provides the key to the component values, given in TO/049 simply as "R1" and "C5", and so on. The red shapes are the PCB traces. A larger copy of TO/049 will be made available shortly.

That sheets such as these existed in 1964 is clear from OS/064, a block diagram for the single manual Continental, dated November of that year:

Detail of OS/064, drawn by Albert Hogben in late November 1964, referencing TO/049 and OS/027.

Quite when JMI kicked off its "TO" series of diagrams is unknown at present - 1964 certainly, possibly even late 1963, when production of the single manual Continental had reached a more settled point (in relative terms at any rate).

Although copies of both OS/064 and TO/049 were sent to Thomas Organ (presumably in connexion with the "Million Dollar Deal" of late 1964), Thomas does not seem to have explicitly referenced or illustrated the sheets in its service literature until early 1967 (cover illustrated below). The main service aid up to that point was the "Pocket Reference Guide of Replacement Parts", its photographs providing the principal means of helping the owner / service repairman identify and order the requisite replacement board or boards.

Thomas Organ, "Pocket Reference Guide of Replacement Parts", 1966. But for the omission of two capacitors at left, the board pictured is laid out in accordance with TO/049.

Below, the generator board for "B" in Continental TC1888, its arrangement (though not component types) corresponding to the picture inset above. Organs with TC serial numbers in the 1500s, however, have an entirely different type of board; and for organs with TC numbers in the 1200s and lower there is yet another (one at the very least).

Detail from Continental TC1888.

Repairmen in England in 1963 and 1964 needed to be as much on their mettle when it came to these boards as Thomas repairmen had to be in the later 1960s. Parts from various production runs were often not interchangeable.

Clearly such things were known to Jennings. When discussions surrounding the move to the West Street Works began in Spring 1964, one of the hopes must have to been improve the consistency of production. So far as one can tell, the assembly of organs - transferred from Dartford Road - was in full swing there by early 1965.

America (and versions of the generator boards)

Below, the outer cover of the Thomas Organ service manual from 1967. As mentioned above, this superceded the handy "Pocket Reference Guide of Replacement Parts" issued by Thomas in 1966, the main point of which, as far as organs were concerned, was to illustrate the differences between the tone generator boards installed in the three main types of single manual Continental: the V301J (Jennings, produced at Erith) and the V301E and V301H (produced in Italy), along with the V304 (Jaguar). Notes were also provided on the double manual Continentals: the V303J (Jennings, produced at Erith) and the V303E (made in Italy).

In the UK and Europe of course the Continental was known simply the "Continental", and the double manual as the "Super Continental". "V" numbers were only used by Thomas.

Also to add that through to the autumn of 1965 (when the "Super Continental" was brought to market), Jennings was sole manufacturer. EKO did not start producing its versions until early to mid 1966.

By one of those strange quirks, the Thomas manuals of 1967 (and later) preserve a type of Jennings circuit diagram - a "TO" ("Transistor Organ") sheet - that is now extremely scarce in English sources. There were at one time around 50 different "TO" sheets, for the most part illustrating component layouts of boards and assemblies. The Thomas manual of 1966 to some extent copied Jennings in this respect (as one might expect), but with photographs rather than drawings - a much better way of doing things.

Thomas Organ "Vox Organs and Accessories" service manual cover, 1967.

The copy pictured above contains sheets for the Vox Jaguar organ, but otherwise only accessories. These Thomas manuals are often a little quirky; it is hard - these days at any rate - to find two the same. Below, a fuller collectrion from early 1967.

The circuit diagrams for the Continental, all of which have long been known, are copies of JMI's, quality leaving something to be desired. The "complete schematic" - Thomas reference number 38-5495-0 - is not encompassed in this collection, possibly because it had not yet been brought into being (i.e. copied from JMI's TO/065?). The earliest copy of known date is from September 1967.

The other elements are Thomas's own though, the overview of types of tone generator board (with good photos) having been prepared initially for the "Pocket Manual" of late 1966.

Inner cover page.

Material relating to the V301J.

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