Early Vox AC30 copper panel chassis, Top Boost controls integrated
Produced for JMI by Westrex, late 1963 to late 1964 - probably around 200-300 made
For the time being this page stands as a sort of adjunct to the main page on chassis with copper panels, Top Boost controls integrated. It may be useful eventually to merge the two, or perhaps even make this the page the principal one.
Below, an overview of the earliest chassis with integral controls, produced by Westrex for JMI in the last quarter of 1963 and fitted by JMI to select Twins and Super Twins in the months and weeks prior to the release of the Expanded Frequency AC30s in early 1964.
The very earliest chassis to have come to light so far are those of serial numbers 9029, a Super Twin, and 9158, a Twin. Both are likely to be genuine (i.e. the chassis are in their original boxes with original serial number plates). The plate of the latter has "TB" stamped with JMI stamps.
A Twin purporting to be serial number 9836, chassis with integrated Top Boost, is a later put-together. The serial number plate is a repro/fake, so all bets are off unfortunately.
Component date codes
Component date codes in the very earliest units are generally of June/July '63 and earlier.
Chassis, the serial number of the AC30 from which it originally came unknown. TCC cathode bypass caps with "UC" = March 1963 for their manufacture.
The same chassis as above, TCC cap with "UF" = June 1963. The cap with plain metal can next to it probably has "UG".
Below, pictures of chassis with later TCC bypass caps, date codes "UF" - June 1963 - and later. At present however, it is not really possible to say whether the presence of these indicates beyond doubt a later batch of chassis. For the moment, the important thing is to collect and document the data.
A later Westrex-made Top Boost chassis, cathode bypass caps with the date code "UF" = June 1963.
A detail to show a TCC plain metal can with "UG" = July 1963 for its manufacture.
As mentioned on the previous page, the value of the cathode resistor, where known, on these chassis, is 50R, ie. the new value introduced in mid 1963. The move from the older value (80R) is noted on the circuit diagram in the entry added on 14th June 1963. The date code of the resistors used for the Top Boost chassis, again where known, is normally "UG" = July 1963.
It was only when JMI got going with the new Expanded Frequency AC30s that more Top Boost chassis were fitted to AC30 Super Twins and Twins.