Original valves (from factory) in Vox AC30s
1960-1968
The original preamp valves and GZ34 from a chassis produced by Westrex in mid 1964.
Below, a provisional list of AC30 Twins that survive with some or all of their original valves. There will doubtless be others (pictures permitting). A number of "possibles" have been included too.
The commonest valves are Mullards. Brimars, however, were normally fitted by Burndept from late 1962 to mid 1964. In 1967 it is likely that Tungsrams were used, though how regularly is not clear at present. They may also have been used from time to time in previous years.
A section on Super Twins will follow shortly.
From 1961 through to 1964/1965, Mullard valves were given two sets of dates at factory: the first being the date of manufacture (a four element code, letter-number-letter-number); the other being the date on which the paint/print was applied (a two letter code, one letter either side of the main design).
The old-style Mullard date code (for the manufacture of the valve) had only three elements - letter-number-letter. See the entry for serial number 4347, below.
It is clear from at least four surviving AC30s that Canadian-made Mullard EL84s were sometimes fitted at factory in early 1964.
- serial number 10317 (a Twin, Burndept-made chassis);
- serial number 2791 (a Super Twin, Westrex chassis);
- an "Expanded Frequency" AC30X (Westrex-made, copper panel with integrated Top Boost controls);
- a Twin (Westrex chassis) with a number originally in the low 11000s.
Such valves were imported, either by Mullard or some intermediate supplier used by JMI, to make up for a short-fall in production at the main factory in Blackburn. Further examples are likely to emerge in due course.
Paint code "KG" = July 1963. The manufacturing code (not visible in this pic) is "r3D1" = 1st week of April '63. The small "r" indicates the Ontario factory.
EL84 with manufacturing code "r3G1" = Ontario factory, 1st week of July 1963.
White-print Mullards (1960-1962)
The valves fitted to pre-1963 AC30s will in almost all cases have been white print Mullards, date codes varying over a range of months in a given amp.
To give some context, the original white print Mullards in AC2 serial number 2027, very late 1960 / early 1961, have date codes "B0K" (November 1960); "B9D" (April 1959); "BOB" (February 1960); and "BOK" (November 1960 again).
Yellow-print Mullards (1963-1965)
Various attempts have been made over the years to explain why yellow print was introduced, the principal suppositions being to indicate (a) that valves printed in this way were of higher quality; (b) that they were in fact "seconds" ("B-grade"); or (c) that they were intended mainly for equipment manufacturers (of radios, televisions, amplifiers, and so on) rather than the general public. Supposition (c) is almost certainly correct, though it is clear that some yellow-print valves were boxed up for sale in shops. Some of the main themes, batted back and forth, can be found on this thread.
As for JMI, yellow-print Mullards appear to have been used from around AC30 serial number 6000 (early 1963) through into later 1965 (early fixed bias AC100s). The general consensus seems to be that Mullard first used yellow print in 1963.
Just to note that Mullard was not the first to adopt yellow print. Brimar had already done so in the 1950s. Yellow-print Brimars are often to be found in Jennings Univoxes.
Brimars (Late 1962-1966)
Often fitted as an alternative to Mullards in AC30s, but rarely used by JMI for other models in 1963 and 1964. Bellow, four block-print Brimar ECC83s from an AC30 from Spring 1963. "BVA" stands for "British Valve Assocation".
The ECC83s have the date code "5I2" = 5th week of Sept. 1962 for their manufacture.
Brimar and Tungsram re-branded Mullards (1966-1967)
Short section forthcoming
The categories in the outline below are: serial number (or range if the plate is missing); the contractor responsible for manufacturing the chassis; notes on the valves themselves; notes on other component date codes in the amps in view.
4347
Dartford Road
Probably the white-print Mullard EF86. Old three letter code "B0E" = May 1960.
Black panel AC30/4. Capacitor with date code "RD" = April 1960
4447
Westrex
White print Mullards: EF86 with "B0F" = June 1960; three EL84s with "B0F" = June '60; GZ34 with "B0J" = October '60; ECC83 with "B1B = February 1961.
Components with March 1961 date codes.
4981
Westrex
According to John Chambers, who serviced the amp, a full set of original valves (white-print Mullards).
Components with mid 1961 date codes.
5300s
Westrex
White print Mullard ECC83s - "B1G3", "B2D1", "B1G5" = 3rd week July 1961; 1st week of April 1962; 5th week of July 1961.
Components with date codes in the last third of 1962.
5672
Burndept
No electronic changes. Valves unknown at present.
Components with date codes in the last third of 1962.
6038
Westrex
Yellow-print GZ34 with paint date code "KE" = May 1963. Yellow-print EL84s, and preamp valves probably original too.
Filter capacitor dated "UE" = May 1963.
6097
Westrex
A mixture of original and replacement valves. At least one of the EL84s has the paint date code "JJ" = September 1962.
Celestions dated November and December 1962.
6920
Westrex
White and yellow-print preamp valves, paint date code "KA" = January 1963. EL84s have date code "B2K2" = 2nd week October 1962.
Components with mid October 1962 date codes.
6948
Burndept
Two original Brimar preamp valves survive along with the Brimar GZ34 and EL84s.
Wodens with January 1963 date codes.
7000s
Burndept
Brimar ECC83s with date code "5I2" = 5th week of Sept. 1962. Mullard-made Brimar GZ34: "B2J3" = 3rd week of October, 1962. EL84s replaced in 1965.
Chassis no. 01518. Components with late 1962 and early 1963 date codes.
7426
Westrex
White-print Mullard ECC83s possibly original.
No date codes currently known.
9078
Westrex
Two yellow-print Mullard preamp valves survive with "KI" paint codes = Sept. 1963.
Haddon transformer with July 1963 stamp.
10317
Burndept
At least one original Brimar ECC83 and ECC82. EL84s are Canadian-made Mullards with date code "R3D1" = first week of April 1963, paint codes "KG" = July 1963.
Woden transformers October and December 1963.
Low 11000s
Westrex
Yellow-print Mullard preamp valves with "KK" paint codes = Nov. 1963. The EL84s are Canadian-made Mullards with date code "R3G1" = first week of July 1963.
Tone pot with date code "AL" = Jan. 1964.
11066
Burndept
Brimar preamp valves, date codes currently unknown. The EL84s are yellow-print Mullards with paint codes for some month in 1963, and "LA" = Jan. 1964.
Woden transformers with Jan. 1964 codes.
11769
Burndept
Brimar-branded Mullard EL84s, date code "B3?2" - second week of some month in 1963.
Chassis no. 3004 (or 3094). Wodens dated October and December 1963.
11873
Burndept
Mullard GZ34 with the date code "B4A3" = 3rd week of 1964.
Woden transformers with Jan. '64 date codes.
2791 (Super Twin)
Westrex
Yellow-print Mullard preamp valves with "KK" paint codes = Nov. 1963. The EL84s are Canadian-made Mullards also with "KK" paint codes = Nov. 1963.
Tone pot with date code "AL" = Jan. 1964.
12000s
Burndept
Original yellow-print EL84s with paint code "KG" = July 1963.
Grey panel, Top Boost, chassis number 4916.
12242
Westrex
Two yellow-print ECC83s with paint date codes "KK" = Nov. 1963. Possibly original.
Celestions with February 1964 date codes.
13098
Burndept
A number of Brimar preamp valves, one with "1B4" = 1st week Feb. 1964. The Mullard GZ34 has "B3K2" = 2nd week Nov. 1963.
Celestions with Pulsonic cone codes 4H1777 (c. March 1964).
13099
Burndept
Perhaps the original GZ34, date code unknown.
2960 (Super Twin)
Westrex
Yellow-print Mullard EL84s with "B4Dx" manufacturing code = some week April 1964. GZ34 with "LC" paint code = March '64
Main preamp filter cap. "UG" = July 1963.
14000s
Westrex
The four yellow-print ECC83s have the date code "B4C5" = last week of March 1964. Paint date codes are "LE" = May 1964. The ECC82 has "KH" = August 1963.
Component date codes "UM" and "VA" December 1963 and January 1964.
14491
Burndept
The EL84s had paint codes "LD" = April 1964
Capacitors with "VG" date codes = July 1964.
15029
Burndept
One of the original yellow-print Mullard ECC83s has the paint code "LE" = May 1964.
Hunts cap. with date code for 22nd week 1964.
15050
Burndept
Perhaps the original white print Mullards in the preamp. The white print GZ34 has the manufacturing code "B4C2" = 2nd week of March 1964.
Mullard mustard caps with "B4N" = second quarter of 1964.
15952
Burndept
Two of the yellow-print ECC83s have the paint code "LA" = January 1964
Mullard mustard capacitors, second quarter of 1964.
16000s
Burndept
Yellow-print preamp valves, paint codes "LE and "LF" = May and June 1964. EL84s with date code "B4B4" = 4th week of February 1964.
At least one capacitor with the date "VF" = June 1964.
17169
Burndept
An original set of white print Brimar valves.
At least one capacitor with the date "VJ" = Sept. 1964.
17505
Burndept
An original set of white print Brimar preamp valves.
Hunts cap. with the date "VF" = June 1964.
17663
Burndept
A yellow-print Mullard ECC83 with paint code "LH" = August 1964.
Wodens with September 1964 codes.
18000s
Burndept
EL84, yellow-print, paint date code "LH" = August 1964.
Chassis no. 8407. Woden transformer dated August 1964.
18052
Westrex
Two yellow-print Mullard EL84s with paint code "LJ" = October 1964.
Celestion silvers with Pulsonic cone code 7H1777.
18128
Burndept
Yellow-print Mullard ECC83 with paint code "LH" = August 1964. Possibly also an original Brimar ECC83.
Speakers dated 2nd December 1964.