Assembled by Burndept Electronics.

For valve rectified amps with serial numbers in the 2000s, see .

During the course of 1965, production of AC50s was moved away from Triumph Electronics in Purley to the Vox/Burndept Factory at Erith, which could produce greater numbers. Orders from America were such that a great ramping up of output was required. Triumph eventually moved on to other things - principally PA equipment and some of the smaller amps.

But it was Triumph though, that kicked off production of the solid state rectified AC50 - the AC50 Mark 3 - many examples . Burndept only really got into its stride later on in the year, so there are relatively few amps on this page.

Its amps are distinguishable by the presence of chassis numbers stamped on the aluminium upright of the preamp underneath the input jacks; WIMA capacitors, and heavier-looking transformers, some with solder-tags under chassis.

The new chassis, lacking the hole for the rectifier valve, were the same as the ones that Triumph made for the amps it produced. Other features are .

A copy of the schematic - OS/072 - .

Below, a register of amps. If anyone knows of others that have not yet been included, as ever do let me know.

Solid state rectified AC50s (without the brimistor)

Serial number unknown - currently in Europe

Capacitors mounted axially on top of chassis. Transformers presumably the same as those in the amp below (perhaps Wodens, though no date code is visible on top). The voltage selector is set at 160V.


Serial number unknown - currently in the USA.

No serial number. Wima capacitors in the preamp, "3" chalked on the inner face of the back board, one Woden transformer remaining - one can tell by the speckled aging of the shrouds. The transformers used by Triumph do not age in this way.

Serial number unknown - currently in the USA

Capacitors mounted axially on top of chassis. The transformers, probably by the same manufacturer as those in the amp above, have solder tag terminals on their undersides. WIMA capacitors indicate assembly by Burndept.

Amps for which definitive info is lacking

At least one of the amps below is definitely solid state rectified - only two valves are evident through the top grille. The others could on the other hand easily be valve rectified - see the amps for comparison. Note however, that 2793 and 2795 do not have white inputs.

Serial number 2793 - location unknown

Serial number 2795 - currently in Europe

The voltage selector is set at 225V.

Serial number 2924 - currently in the UK

Sold on ebay UK in 2013. Pictures only of the outside.


Serial number unknown - location unknown

Solid state rectified, two-line serial number plate, white warning plaque, connector (now removed) on the back panel. But it could be that the amp belongs on the next page, serial numbers in the 3000s.