Notes on the "Treble" circuit will be provided shortly. "T" denotes Treble voicing - schematic also drawn in September 1964: OS/056. No early schematic survives for the bass circuit, though in relevant respects most amps (from 1962 on) follow OS/065, drawn in September 1964. Just to note again, "N" indicates "Normal" voicing (schematic OA/026 and OS/065), "B" is bass voicing. Serial number plates are still hand stamped. The preceding letter is always the month (A-L).
T530) - date codes in mid 1964, the final "H" in the code can indicate 1963 or 1964.
Speakers in "standard" AC30s continue to be the Celestion blue (alnico magnet, Celestion part no. Back boards as a rule now have radiused corners rather than square. Dark brown Dubilier resistors are found along with white Eries.įrom early 1964, most Twins have Burndept-made chassis those produced by Westrex were generally alloted to Super Twins.Ĭabinets are in the main covered in black basketweave vinyl, though "pebble" ("dimpled") vinyl was evidently used from time to time, and likewise smooth black or charcoal vinyl. Further details on AC30 transformers in general can be found on this page.Ī good indication that a chassis was assembled by Westrex is the presence of Albion tranformers. The Woden part numbers were, in order: mains transformer 72318 output transformer no. Serial number 11954 - date code is "AV" = January 1964. True "Treble" chassis regularly (though not infallibly always) have TREBLE stamped in red BASS on bass-voiced amps. The only way to determine voicing for certain is to check the value of components at key points in the circuit. At least one amp on this page with a "T" on its serial number plate (to denote "Treble" voicing) is actually a "Normal" model. The official circuit diagram for the AC30 Treble was released in September/October 1964. There are precious few Burndept-made Normal, Bass, and Top Boost chassis from this period. In Spring and Summer 1964, JMI instructed Burndept, one of its main contractors, to concentrate on the production Treble chassis. The new thing in the 11000s is the appearance of the new "Treble" model.
Also encompassed below, some of the last Super Twins that were given numbers in the main AC30 sequence.
Continued from the page on AC30s with serial numbers in the 10000s.
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