Dubilier Capacitors

A short note on the filter and cathode bypass capacitors in AC80/100s. At first these were light gold-coloured Dubiliers, presumably sourced direct from the Dubilier factory in North Acton (a short step from Willesden, where Westrex assembled the chassis for Vox).

The Dubilier Condenser Company, Ducon Works, North Acton - the complex in the upper centre of the picture is the Dubilier works. Image from the fab .

In late 1964, however, Vox/Westrex seems to have bought in from TCC - the "Telegraph Condenser Company", also based in North Acton. The TCC capacitors were generally green "Micromite", printed in beautiful, heavy, Gill sans typeface.

One also finds in amps from late 1964 main filter capacitors (100uf, 500v) made by Daly Condensers of Ealing, West London (West Lodge Works, The Green, Ealing, W5).

But TCC and Daly were used only sparingly early on (generally in black panel amps). Dubiliers were the norm, and the company continued to supply Vox when production of the AC80/100 was moved from Westrex to Burndept Electronics (in Erith) in early 1965.

Green TCCs did become standard later on though with the advent of the fixed bias "100W Amplifier" in summer 1965.

TCC capacitors

Pic. from the wonderful . Note the statement of "Peak Working" and "Surge" voltages.

The caps in question, as marked on the schematic (for which, see lower down this page), are:

C1 - 8uf, preamp main filter (but 16uf always fitted in practice).

C3, C4 - *25uf, preamp cathode bypass.

C9 - 32uf, preamp main filter.

C10 - 50uf, preamp main filter (but 32uf always fitted in practice).

C14 - 8uf 150v, bias smoothing.

* cathode bypass caps were TCC "Micropack"

So far no amp has come to light with 8uf and 50uf main preamp filter caps. The values were evidently simply carried over from the "AC80/100" schematic (and no AC80/100 has come to light with these values either).

Most of the grey panel AC80/100s have blue Hunts 25uf caps for the preamp valve cathode bypass (C3 and C4). The change to the light gold 25uf TCC "Micropack" seems to have taken place between serial numbers 392 and 420.

Below, a TCC (Telegraph Condenser Company) folder of technical bulletins from 1962. Green TCC micromite electrolytics were used in AC100s from early 1965 through to 1966.

Note that values are given both for "Peak Working Volts" and "Surge Volts".

Daly capacitors

Capacitors made by Daly first make their appearance in AC80/100s in late 1964, the caps in question being the main filters - 100uf, 500V. Dubiliers were the norm, however, and Dubilier continued to supply Vox when production of the AC80/100 moved from Westrex to Burndept Electronics (in Erith) in early 1965. Vox bought in from Daly from time to time in subsequent years though.

Mullard BY100 diodes

Mullard BY100 rectifier diodes

The Mullard pricelist of August 1965 gives the price, among other things, of the Mullard BY100 rectifier diodes used in AC80/100s, AC50s, the "100W Amplifier", and the AC100 Mk2 - 11s 6d each in old money, and around £10 each today in relative terms. But Vox presumably had a better (wholesale) price.

Amphenol connectors are here.

Mullard EL34 power valves.