LARGE BOX AC50s - late 1964 to early 1965

Valve rectified amps, part 3

Assembled at Erith (Vox Works / Burndept Electronics). Dome voltage selector.

Vox Ac50, large box, serial number

On Burndept Electronics, which shared a building with Vox off West Street in Erith, Kent, .

The earliest Burndept-made AC50s have one set of white jack input sockets (normal channel) and one set of black (brilliant channel).

Serial number plates are fully machine-stamped - both the "AC50" and the serial number itself. Boxes with plates already fitted to the backboards were provided for chassis on site.

For amps made by Triumph in late 1964 and the first half of 1965 the process was different. Finished chassis were transported in batches from Purley to Erith, where boxes with serial number plates were supplied. The system does not seem to have been particularly orderly however. Certain chassis were clearly stored for some time (either at Purley or Erith) before being given boxes. There are sizeable disjunctions here and there between serial number and "build type".

Characteristics of amps made at the Vox / Burndept Works, Erith

Woden transformers and chokes are used instead of the unmarked silver-shrouded units that Triumph employed from the beginning of AC50 production.

Chassis have serial numbers stamped on the flat of the aluminium underneath the input jacks.

WIMA capacitors figure in the preamp instead of "mustards". Main filter caps on the upper chassis are often upright radial types rather than horizontal axial.

Dedicated mains sockets are now provided on the back board - normally the Cannon LNE-32, also used in the AC80/100s built by Burndept. Previously the mains leads had been hard wired to the "ON" switch and fastened to the slider board with a clamp.

Voltage selectors are of the dome type.

Guitar speaker cabs still have two Celestion silver alnico T1088s and the Midax horn. Bass cabs - the "Foundation Bass" - have a single Goodmans Audiom 91, black label, 50w power handling.

A good number of these amps were exported to the U.S.A. following the "Million Dollar Deal" made with the Thomas Organ Company in late August 1964.

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

Serial number 2269 - whereabouts unknown

Grille cloth replaced, and voltage selector removed. Arrow black plastic bat switch.

Serial number unknown - currently in the UK

The Woden output and mains transformers have the code JV = September 1964; the choke has HV = August '64. Pictures originally

Serial number 0236 (2036?) - currently in the USA

Burndept chassis number visible in the last picture. One of the white input socket nuts survives. Still holes in the chassis for upright filter capacitors, but the new style of axial clamps now in place. The transformers are Wodens, with unpainted shrouds - note the corner fixings. The code on the choke is "HV" = August 1964. The box is a North Coast Music replacement.

Serial number 2500 - currently in the USA

Thanks to Gene for the note on the existence of this amp

Serial number 2508 - whereabouts unknown

No view of the chassis, but very probably valve rectified. Note the hole on the back panel (and the two small screw holes) for a Cannon LNE-11 power connector. In the box, the stickers of H.P.A. Electronics, Richmond, North Yorkshire.

Serial number 2530 - currently in Europe?

Sold on ebay some time ago. A slightly split slider board, but otherwise in good condition. Voltage selector set to 225v.

Serial number 2532 - currently in Italy

Currently in Italy - link here. Valve rectified, two white input jacks, and a replaced logo, more in line with the date of the Dynamic Bass cab which accompanyies.

Serial number 2553 - currently in Europe

One of the white nuts from the normal channel input jacks has been moved to the brilliant channel.

Serial number 2555 - currently in the UK

Chassis 0197. One of the original white jack socket surrounds survives. Preamp filter caps replaced; WIMA signal caps still in place.

Serial number 2559 - currently in the USA

A full rig in nice condition. Pictures from J. Elyea, Vox Amplifiers. The JMI Years (California, 2009), pp. 432-434. Preamp valve sockets replaced, tall feet added, and a new axial filter cap to replace one of the original upright units, but otherwise pretty much intact. The choke has the date code "JV" = September 1964. The speaker on the right-hand side looks as though it has come from another source - not the wrongly aligned label.

Serial number 2562 - currently in the UK

Individual letters making up VOX. Original connectors on the back panel. The white jack plug rings have been swapped to the treble channel. Bias adjustment points have been added on the shelf.

Serial number 2609 - currently in the USA

Great condition. Only a few capacitors changed in the preamp. Woden transformers with the code "JV" = September 1964. Original Cannon mains connector still in place.


Serial number 2612 - currently in the USA

Chassis no. 140. The Woden transformers have the date code "JV" = September 1964. The choke has been replaced. Four black plastic jack socket nuts on the control panel (instead of the normal two black, two white). In company with serial numbers 2559 and 2609, immediately above, and 2620 below, the left-most filter capacitor in the preamp is a grey Radiospares. The date codes of the blue Hunts capacitors are unknown at present. Note the Daly and Radiospares caps on the bias board (underchassis).

Serial number 2620 - currently in the USA

Sold on ebay US in 2011. Chassis number 0120. Code on the choke is "JV" = September 1964. The code on one of the pots is "IL" = September 1964.

Originally accompanied by a Foundation Bass cab in the same cloth. Perhaps a special order as the amp is almost otherwise unchanged.

Used by in the studio.

Serial number unknown - currently in the UK

A good looking amp, though pictured after an unfortunate bump. Images originally .

Serial number unknown - currently in Scandinavia (?)

Valve rectified, two white input jacks. The voltage selector has been removed, in its place a printed sticker. "Woden" is just visible on the mains transformer. The output transformer may be a replacement (with the shrouds of the original).

Serial number unknown - currently in the USA

Serial number plate missing, but white jack sockets and Cannon LNE-11 mains socket still in place.

Serial number unknown - whereabouts unknown

Sold on ebay in 2005.

Serial number 2644 - currently in the UK

Chassis number 0240. A replaced mains transformer, and a few other components here and there. The Woden output transformer and choke remain, date codes respectively "JV" and "HV" = August and September 1964. Pot codes "KL" and "IL" = September and November '64. The blue Hunts capacitors have the code: "TWT" = 40th week 1964.

Serial number 2717 - currently in the USA

The two white jack plug rings remain. The original transformers and choke are also in place. A good number of components have been renewed, however. The presence of the Wurth surgistor above the choke indicates that the amp was in the USA at an early date.

Serial number 2952 (?) - currently in Spain

A high serial number for a valve rectified amp with white input sockets. Pictures originally .

Serial number 3088 - currently in the USA

Sold recently (April 2017). In company with the amp below it, a straggler in terms of valve rectification. Triumph had gone steaming ahead with solid state rectified amps. Without any date codes, it's difficult to place this amp. But it seems likely that Burndept was simply using up available chassis as they came to hand.

Serial number 3092 - currently in the USA

A nice Burndept-made AC50. The input jacks have been replaced, so too probably the mains socket (with a later Amphenol). The Woden mains transformer apparently has the date code "JV" = September 1964.

Serial number 3098 - currently in the USA.

Similar to the amp immediately below. Mains transformer and choke have the Woden date code "JV" = September 1964. One of the pots has the code "IL" = also September 1964. Note the presence next to the choke of the grey Radiospares suppressor capacitor (not on the schematic), added by JMI to amps destined for export to the USA.

Note that this amp has had a "surgistor" added (last pic, above the choke) - a sort of surrogate for the brimistor fitted by Thomas Organ centres in the 1960s. In the case of a valve rectified amp, as this is, the surgistor is completely redundant, alas.

Serial number unknown - currently in the USA.

Sold on ebay in September 2012. Burndept-made - note the Woden transformers. Both the choke and mains tranformer have the code "JV" = September 1964.

Serial number unknown - currently in Europe

Input jacks apparently changed, along with a spread of elements in the preamp. The amp's Woden transformers still in place.

Serial number unknown - currently in Europe

No clue as to serial number. White rings for two of the input jacks, but the amp may not be valve rectified - the potential position of the rectifier (seen through the grille) looks peculiar. This entry may have to be moved in due course.

Serial number 3226 - currently in the USA

Chassis no. 0272. Probably one of the last valve rectified AC50s to be made. The Woden choke has the date code "HV" = August 1964. The Woden logo is just visible on the mains transformer. In common with serial number 3098, above, a surgistor has been fitted above the choke.