Woden transformer, date code "DX" = April 1966, in serial number 21019.

This page picks up from the page on AC30s with serial numbers in the 20000s.

As in the 20000s, Control panels are grey. Dome voltage selectors occur as standard, as they are for amps with serial number in the 17000s and later. Chassis were assembled by Burndept, the contract with Westrex having ended in early 1965 following JMI's move (expansion) into Burndept's West Street Factory in Erith - the "West Street Works".

In late 1965 production began to slow. The European market was still strong, but fewer orders for AC30s came in from America. The Thomas Organ Company, which had the rights to the "Vox" name in the States, preferred to promote its solid state range. The last major order from JMI came in the summer of 1966, probably for the most part accessories and spare parts.

The four models are still: "TB" for "Top Boost", designated "TB" on the serial number plate, the circuit's controls normally integral in the control panel; "Treble" designated with a "T"; and "B" for Bass. The two last had their own schematics, in order: OS/056 and OS/057. "Normal" voicing no longer seems to be an active designation. Some notes on the treble circuit, which was new in 1964, can be found on this page.

Number plates have three lines - MODEL No., SERIAL No.. and RATING (power consumption) - come in in the high 20000s. Chassis numbers are generally stamped on the aluminium preamp upright underneath the input jacks rather than under the voltage selector.

Around a third of the way into the 21000s, a new style of control panel comes in, the JMI logo presented as separate letters on separate parallelogram backgrounds (as on the copper amps) rather than as a single block that runs into the silver bounding lines.

The earliest amp on which this new type of panel has come to light is serial number 21397, see further below.

Woden transformers are the norm, year codes being "V" = 1964, "W" = 1965, and "X" = 1966, the first letter in the two-letter sequence standing for the month: "DX" = April 1966 for instance. A large batch of Wodens was evidently ordered in Spring 1966 - examples dated "DX" are found well into 1967. See also the page on later AC30 Super Twins.

During the course of 1966, white 1/4 watt Erie resistors began to be used again instead of the brown Dubiliers.

Silver alnico T1088s are standard. In mid 1966 Celestion revised the design, introducing a dedicated board for the solder terminal between the spokes of the frame. Earlier T1088s have terminals on the frame itself. An overview of "silvers" (really "poly grey") can be found on this page. Grille cloth is normally black. Plastic corner protectors have single pins through to the low 21000s. Thereafter double pins are the norm. But as ever there is no sharp transition.

Note that the majority of serial numbers of amplifiers in the range cited by Jim Elyea - listed in his book and noted in the sections below - end in "0". How can this be? The suspicion is that at least some of these are simply placeholders and guesses: i.e. "serial number 21410 will have been reached at June 1966".

If anyone knows of further amps that should be incorporated on this page, do let me know.

Serial numbers in the 21000s

Serial number 21019 TB

Chassis number 14021. The Woden transformers have the date code "DX" = April 1966. In the preamp a mixture of Mullard mustard and WIMA caps. Some of the date codes on the former can be seen - mostly B4N = second quarter of 1964, a large number evidently having been ordered in early '64. The gold-coloured choke (part no. 66429) is of the type found in certain AC100s. The Celestions are of the earlier type with termainals on the frame, rather than on a discrete terminal board.

Serial number 21051 T

No shots of the electronics. Three-line serial number plates. The Celestion T1088s have terminals on the frame (i.e. not new style).

Serial number 21056

Chassis number 12943 stamped on the left side of the preamp. Woden mains transformer with date code "EW" = May 1965; output with "HW" = August 1965. A mixture of Mullard mustard and WIMA caps. Cabinet produced by "Gla-Rev", its white stamp (stencil) inside. The back-boards have square rather than radiused corners. Speaker terminals on the frames (as serial number 21051 above).

Serial number 21075

Existence recorded by Jim Elyea

Serial number 21086 - currently in Corsica

Chassis number 12962. The Woden mains and output transformers have the date code "HW" = August 1965; choke "DX" = April 1966. The silver alnicos (T1088s), terminals on the spokes of the frame, have "15DK" and "18HK" = 15th April and 18th August 1965. The mustard capacitors in the preamp have "A4N", "B4N" and A5W", respectively first and second quarters of 1964, and first quarter of 1965. Thanks to Philippe for the pictures and details.

Serial number 21098 TB

In good external order. Exported to Sweden early on - the voltage selector removed (to conform with Scandinavian electrical regulations) and a plate to cover the resulting hole. Woden transformers, the output with date code "KV" = October 1964; the choke with "AX" = January 1966; and the mains transformer with "HW" = August 1965.

Serial number 21126 TB

Chassis serial number in the 7000s - probably 07581, so likely to have been removed from another amp. Albion transformers. Still the old-style JMI logo on the control panel. An original hand-stamped serial number plate. The speakers have been replaced.

Serial number 21176 TB

Chassis number 13156. The Woden transformers and choke have the date code "DX" = April 1966. Mains and output were stamped at the West Street Works, "KC.2" and "NT". These stampings survive on a (small) number of other amps too. In the preamp, red Lemco, WIMA, and Mullard mustard capacitors, the Mullards with "B4N", "D4N", "B5N" date codes = respectively, second and last quarter of 1964, and second quarter of 1965. Thanks to Paul for the pictures.

Serial number 21190

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21192 - currently in the USA

The Woden transformers and choke have the date code "DX" = April 1966. In the preamp, WIMA and Mullard mustard capacitors (some of the latter with date code "A4W" = first quarter of 1964). The Celestion silvers still have terminals on the frame (rather than on boards). Thanks to Jarod for the pictures.

New-style Celestion T1088s from this point

Solder terminals now on small boards between the spokes of the frame instead of on the frame itself. For an overview of Celestion silvers, see this page.

Serial number 21202

Chassis number 12745. Woden mains transformer with the date code "HW" = August 1965; output transformer and choke have "MW" = December 1965. In the preamp, a mixture of WIMA and Mullard mustard caps, the latter dated "D4N" = last quarter of 1964. One of the gold-coloured TCC cathode bypass caps has "WF" = June 1965. The Celestion T1088s are dated "18GL" and "19GL" = 18th and 19th July 1966. Thanks to Paul for the pictures.

Serial number 21203 TB

Exterior pics only.

Serial number 21270

Exterior pics only. Celestion silvers with terminal boards between the spokes of the frame.

Serial number 21300

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21304

An earlier chassis assembled by Westrex slipped into the box in recent years. The speakers, with terminal boards between the struts, are original to the box (1966).

Serial number 21306

The serial number plate alone sold on ebay in the UK (February 2022)

Serial number 21377 B

Exterior pics only. Celestion silvers with terminal boards between the spokes of the frame. A late and fairly unusual example of a Bass model.

Serial number 21397 TB - currently in Sweden

Probably exported early on to Sweden, where the voltage selector was removed (to conform with local electrical regulations). Mains transformer replaced. The Woden choke has the date code "GX" = July 1966. Red and yellow Lemco signal capacitors in the preamp. The blue Hunts cathode bypass capacitor in the power section has the date code "UYU" = 6th week of 1966.

Serial number 21410

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21418 TB

The earliest instance so far (March 2023) of the new-style JMI logo on the control panel.

Serial number 21500 TB

Chassis number 13246. The Woden mains transformer, stamped "KC" on top in purple ink, has the date code "GX" = July 1966 for its manufacture. Red Lemco signal caps in the preamp. The Hunts cathode bypass capacitor underchassis has "U YU" = 6th week of '66. The original cover and footswitch survive.

Serial number 21512 TB

Super Twin amplifier section. An earlier chassis with copper panel is now in the box belonging originally to serial number 21512.

Serial number 21520 TB - currently in Germany

Thanks to Ralf for the image. Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21581 TB - currently in Europe

Woden transformers with date codes "JX" and "LX" = September and November 1966. In the preamp, red Lemco signal caps. The main preamp filter - made by CCL - has the date "L6" = December 1966. The logo is a 1980s replacement.

Serial number 21608 TB - currently in Germany

Thanks to Stefan for the pic.

Serial number 21620 TB

Three-line serial number plate, machine stamped. In the preamp, red Lemco capacitors; Hunts 25uf bypass caps with date code "UYD" = 8th week of 1966. New-style silver Celestion T1088s with solder terminals on boards.

Serial number 21630

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21632 TB

Chassis number 13477. The Woden transformers have "GX", "HX", and "JX" = respectively July, August, and September 1966 for their manufacture. In the preamp, red Lemco signal capacitors. The original JMI warranty documentation survives.

Serial number 21659 TB

Woden transformers: output has the date code "GX" = July 1966; mains "JX" = September 1966; choke "HX" = August 1966. Red Lemco capacitors in the preamp.

Serial number 21662 TB

New-style JMI logo on the control panel. The Woden transformers have the date code "GX" = July 1966. In the preamp, red and yellow (0.1uf) Lemco capacitors; Hunts electrolytics with date code "WAU" = 19th week of 1966. The terminals of the Celestion T1088s are on boards rather than on the frame. The "TOP BOOST 30" runner is still on the front grille.

Serial number 21693 TB

New-style JMI logo on the control panel.

Serial number 21694 TB - currently in Germany

Chassis number 13448. Thanks to Jürgen for the pics.

Serial number 21740

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21807

Exterior shots only. Three-line serial number plate, machine stamped. Silver Celestions in place.

Serial number 21850

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21855 N - currently in the USA

Serial number 21884 TB

The Woden output transformer and choke have the date code "HY" = August 1967. Mains transformer replaced. The control panel is of the new style with "JMI" as separate letters on separate backgrounds. In the preamp Mullard mustard and red Lemco capacitors.

NEW

Serial number 21935 TB

Chassis number 13209. Woden transformers and choke with date code "KX" = October 1966 for their manufacture. In the preamp, red Lemco signal capacitors and blue and yellow Dubilier coupling caps. The speakers are now new production Celestion blues.

Serial number 21936 TB

Woden transformers and choke with date code "KX = October 1966. In the preamp, red Lemco capacitors; one of the main filter caps has "VF" = June 1964. The cabinet was fitted out (grille cloth, etc.) by May, her name chalked inside.

Serial number 21945 TB

"TOP BOOST 30" runner on the grille cloth (lower right). The Celestion T1088 speakers have terminals on boards.

Serial number 21960

Listed by Jim Elyea, but probably as a "guesstimate".

Serial number 21971 TB

Chassis number 13971. The Woden transformers have the date code "KX" = October 1966 for their manufacture. Thanks to Dillon for the pictures.

Serial numbers unknown

Serial number in the 20000s (?) - currently in the UK

Chassis number 12403. The serial number plate is a reproduction. Grey panel, integral Top Boost controls. The Celestions have the date code "01FJ" = 1st June 1964.

On to serial numbers in the 22000s and 23000s.

Back to serial numbers in the 20000s.