Westrex is probably best known as "Western Electric", makers of high quality sound and projection equipment for cinemas and film studios, first in the USA, then in the UK. In post-war years the company broadened its scope, manufacturing domestic hi-fi equipment and portable PA systems (among other things), and taking on contract work for other companies.

Indeed, at some point in early 1960, JMI placed the assembly of runs of AC6 chassis in the hands of the company - an overview of the model on this page; then later on runs of AC15 and AC30/4 chassis, the latter for the new TV Front (and later split-front) Twins:

TV Front AC30/4 (AC34) - late 1960.

The checker who signed off the amp above evidently also signed off, among many other things presumably, a 40-50 watt cinema amplifier sold under the Westrex name:

Westrex tag in a 40-50 watt cinema amplifier, late 1950s/early 1960s.

A page on Westrex tags can be found here. To keep things orderly, JMI added a "W" on the serial number plate to indicate that the company had manufactured the chassis in view:

AC30/4 serial number 4669, BASS voicing.

In the spring of 1961, assembly of runs of AC30/6 chassis was also passed to Westrex, doubtless a means of helping increase output. The Dartford Road Works were not large. The assembly of AC10 and AC15 chassis was subsequently contracted out to Westrex too - in late 1962.

Being conveniently close to the North Circular Road, it was an easy matter for Westrex lorries to motor down to and up from Dartford Road.

Dick Denney

Dick is often reported as saying that AC30 chassis made by Westrex were his "favourite" or preferred type. This it turns out was the view common at JMI - not just Dick's singular opinion. Rodney Angell, who tested amps prior to despatch, was equally clear about Westrex-made chassis. It was not that they were inherently better in any way than those assembled by Burndept (in terms of components and so on), but simply more carefully made. In other words, quality control was more exacting. Burndept chassis often had cold solder joints. It is as unprosaic as that, and has nothing to do with the "tone", imagined or otherwise, of particular brands of transformer or capacitor.

Characteristics of Westrex-made chassis

i) - Perhaps the most obvious characteristic is the presence of red dye on the solder joints, added to indicate that the joints had been checked.

ii) - Westrex used white Erie resistors at first (through to late 1962), then brown 1/2 watt Dubiliers through to 1965. Burndept Electronics, brought in as a contractor in the autumn of 1962, always used Eries (through to 1968).

Detail of serial number 6038 showing the red dye on the solder joints and brown Dubilier resistors.

iii) - As noted on this page, batches of early AC30/6 chassis were produced with a cut-out for the rectifier valve in the wrong place. The hole was filled with a metal blank welded in.

iv) - Westrex-made chassis almost always have Haddon or Albion transformers. Wodens, used principally by Burndept, are extremely uncommon.

v) - JMI mainly used Westrex chassis in its range of AC30 Super Twin amplifiers.

vi) - Treble chassis are often (though not always) stamped "Westrex Treble" in purply-blue. Burndept, JMI's other main contractor, had its own system of demarcation - see this page.

Two Westrex Treble chassis also have "119" (119 Dartford Road?). Whether "119" was simply omitted in the majority of cases or rubbed away later is not known for certain - on balance, the latter seems more likely. Why stamp only certain chassis in this way?

An AC30 Twin, serial number in the 12000s.

An AC30 Super Twin, serial number in the 2800s.

vii) - The first chassis with integrated Top Boost controls were made by Westrex, and marked with an "X" (for "Expanded") in a circle on their underside, along with the checker's initials ("DP").

Detail of the underchassis of AC30 Twin serial number 10348. This one has year of manufacture: - "64".

Chassis signatures

Two chassis signed off at Westrex in early 1963 by Thelsa, one used for AC30 Super Twin serial number 6855, the other for a Twin serial number unknown.

AC30 Super Twin serial number 6855.

AC30 Twin, number unknown.

The earliest instance of a chassis signed off by "DP", mentioned above, is the one used for serial number 6000. One of the latest (currently known) is that of Super Twin serial number 3349, later 1964.

AC30 serial number 6000.

Inspection tags

Occasionally the inspection tags tied on at the Westrex works were not removed by JMI, as below. Normally simply the model of the amp is given, quantity (slightly obvious), and the initials of the final checker. The serial number line was not filled in of course because Westrex assembled nothing more than the chassis itself. Box and serial number plate were provided at Dartford Road.

Thanks to Benjamin, a great shot of the Westrex inspection tag on an early AC30 Super Twin amplifier section, late 1961 / early 1962.

Numbers hand-written on chassis

On certain chassis assembled by Westrex a number was added by hand (in pencil or crayon) - examples below of five different amps with "165". The same person also inscribed "119" and "130" on other amps. The significance of these numbers is unclear at present. "119" naturally makes one think of Dartford Road. But "130" and "165"?

AC30 Twin, serial number 12569.

Serial number unknown. AC30 chassis assembled by Westrex. Grey control panel with integrated Top Boost controls. As above, "T.B." stamped on the preamp upright. Note "165" in red crayon. The same writer wrote this and other numbers (119, 130) on various other JMI amplifiers.

An AC80/100 from the third quarter of 1964 (serial number plate lacking).

AC30 Super Twin, serial number 3021.

AC30 Super Twin, serial number 3863.

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