"BVA" stands for "British Valve Association".

It is rare to find an early AC30 still with its original valves in place and with readable date codes. Often in the case of power valves printing becomes feint through the action of heat. Cleaning can also make date codes near illegible - in some instances paint wipes or flakes away all too easily from the surface of the glass.

Printing on preamp valves is generally less prone to these ravages. One needs very close details indeed, however, to make the codes out, as Brimar printed them very small indeed.

But there are exceptions - a chassis from early 1963, pictured on this page, came with its four original Brimar-made ECC83s and its Brimar branded GZ34. The EL84s were replaced in late 1965 or later. The white print Mullards all have the same date "B5F3" = Blackburn factory (B), 3rd week (3) of June (F), 1965 (5).

Brimar codes work in a different way. The system is set out on the excellent tubemaze site. Brimar-made valves have a date code followed by a "part" code. To begin with the latter:

ECC83s (12AX7) are coded "1574".

ECC82s (12AU7) are coded "161/2161", "571/1571" or "987/3987". "161/2161" is perhaps most common on the ECC82s fitted in AC30s.

EL84s are "795/1795". In the late 1960s Brimar began selling West-German-made EL84s under its own name rather than its own production.

The date code part of the Brimar system takes the form of three elements, often printed very small: - a number, letter, and number. The last number is the year - "4" = 1964. The letter is the month: "A" = January, "B" February, and so on. The first number is the week of the month.

Brimar ECC83 preamp valves: 5I2/1574 = 5th week of September 1962. The second character of "5I2" is a letter "I" denoting September. 1574 is the code for ECC83.

Preliminary investigations show that in 1963 and early 1964 Brimar valves were generally installed by Burndept on the chassis that it made under contract for JMI. From later 1964, Burndept chassis regularly have yellow-print Mullards. Chassis made by Westrex generally have either white or yellow-print Mullards.

Where GZ34s are concerned, Brimar did not produce its own but supplied re-branded Mullards (bearing Mullard date codes).

Brimar-branded GZ34 (Mullard made): B2J(?)3 = Blackburn Factory, 1962, 3rd week of October.

Below, a map showing the relative positions of Dartford, Erith, and Footscray, where the main Brimar factory was based. Brimar's commercial office was on Charing Cross Road, a little way up from the Jennings shop.

Electrical trade journal, February 1962. Advert for Brimar-made ECC82s and ECC83s, among other things.

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