LARGE BOX AC50s - SOLID STATE RECTIFIED
AC50 Mark 3 (Mk III)
Serial numbers in the 5000s - 1966.
Detail of the preamp of serial number 5369
The AC50s at this point were assembled primarily at the Burndept factory (note the presence of the stamped chassis number). Triumph dropped out, or at least was redirected to developing and producing the 4 and 7-series amps for Vox.
The brimistor, an addition of 14th October 1965 to the Mark 3 schematic (to which these amps conform), is now the norm. On the brimistor, see this page. Schematics are available here.
Transformers initially have unpainted shrouds - similar to the ones used by Triumph.
The black-topped transformers come in at around serial no. 5690. These units were NOT made by Albion or "sourced by Geoff Johnson" of Triumph. They were evidently ordered by someone at the West Street works in Erith - the Burndept factory. The same company made the transformers for the solid state range of amps (the Conqueror, Defiant and Supreme, et al.), also assembled at the Vox / Burndept Works.
Part numbers of the potentiometers are: 66181 (500K) and 66520 (1 Meg). These are likely to be Vox part numbers rather than the manufacturer's. Note that the black-topped transformers are nos 66522, 66523 and 66524.
The warning plaque is red; the serial number plate is three-line; speakers in the guitar cabs are still Fanes.
Large numbers of AC50s - in Foundation Bass and Super Twin sets - were exported around the world by Vox. The amplifier was one of the company's most successful lines.
Below, a register of amps. If anyone knows of others that have not yet been included, as ever do let me know.
Serial number 5001 - currently in the USA
Thanks to Jake for the pics.
Serial number 5016 - currently in the USA
Just the box remains.
Serial number 5055 - currently in New Zealand
On the back of the amp, a Dallas Music Industries sticker, giving the serial number 74012239 and designation of the amp as PA110/E. Whether this means that the amp was sold or perhaps re-sold by Dallas, which had taken over the production of the AC50 in the mid 1970s, remains to be seen. Thanks to Dave for the pics.
Further pics from the sale of the amp:
Serial number 51xx - currently in the USA
Serial number perhaps 5105. Paired with a Defiant cab in the first picture.
Serial number 5116 - currently in the USA
Excellent condition. Note the logo - separate letters for V O X.
Serial number 5119 - currently in Europe
Complete with its original mains cable. The speaker cabinet's XLR connector has been repositioned in one of the carrying handle recesses.
Serial number 5172 - currently in Germany
Good cosmetic order, the original Amphenol sockets still on the back panel. No shots of the electronics at present.
Serial number 5173 - currently in Germany
Chassis no. 1923. Pot codes "AM", "JM" and "KM" = January, October and November 1965, so likely to have been made in the first third of '66. Probably used originally by a bass player, as capacitors in the normal channel were replaced early on in England (in company with the 0.1uf coupling caps). The amp surfaced in a music shop in Munich in the 1970s - a few replacement caps having been introduced - and has remained in Germany since. The original speakers are Fane 122/17. Thanks to Gary for the pictures.
Serial number 5180 - currently in Germany
Paired with a Multi-link 4x12" cabinet from the solid state range (1968-1972).
Serial number 5192 - currently in the USA
Serial number 5206 - currently in Europe
Only the back board and serial number plate survive.
Serial number 5212 - currently in the UK
Serial number 5213 - currently in the USA
Original XLR sockets on the back panel. The serial number plate has been moved to cover the hole left by the removal of the mains socket.
Serial number 5216 - currently in the USA
Chassis number 1731. Mains transformer renewed and some changes in the preamp. Original Amphenol sockets still present on the back panel.
NEW
Serial number 5227 - currently in the UK
Chassis number 1765. Brimistor replaced with a resistor array. In the preamp, Dubilier capacitors with "WL" date codes = November 1965 for their manufacture. The pots have "KM" = October '65.
Serial number 5228 - currently in the USA
Pictured with a pair of later Vox LS40 (Line Source) speaker columns.
Serial number 5229 - currently in Germany
Foundation Bass rig, sold originally by the Musikhaus, Wurzburg. Note the 100W Goodmans driver. The cab (with its designation LBA52) is no. 1382.
Serial number 5232 - currently in the USA
Thanks to Paul for the pictures.
Serial number 5237 - currently in the USA
New grille cloth. WIMA caps in the preamp. Visible pot date codes are "KM" = November 1965.
Serial number 5253 - currently in the USA
Chassis number 1915 - a "2" stamped out. TCC, WIMA and green plastic Hunts caps in the preamp. Visible pot date codes are "KM" = November 1965. The preamp and power amp still have their inspection tags - the preamp: "Inspected. 17".
Serial number 5255 - currently in the UK
Chassis number 1797. Cathode bypass caps in the preamp replaced. The WIMA caps for the tone circuit, and the large green Hunts 0.1uf coupling caps, remain.
Serial number 5267 - currently in Europe
Serial number 5278 - currently in Germany
The amplifier: standard Mark 3 chassis, its original control panel replaced with a new repro copper panel. The chassis is now housed in reproduction small box. The speaker cabinet: an original Super Twin, perhaps originally belonging to 5278 (when in its large box), in a Thomas Organ (US-made) trolley.
Serial number 5291 - currently in Germany
The back board of the amp (and perhaps the chsasis inside) seems to be later (a serial number in the 8000s). Note the black escutcheon panel for the jack sockets, the position of the plate, and the presence of a white warning plaque.
The mains transformer still has its part number sticker: "JMI M007A". In the preamp, visible Mullard mustards have "C4N" = third quarter of 1964 for their manufacture. The pots have date codes "JM" = October 1965.
Serial number 5308 - currently in Europe
Serial number 5312 - currently in Europe
The cab contains a set of Goodmans speakers of the type (Goodmans 241H) normally found in Vox Defiants.
Serial number 5345 - currently in the UK
Serial number 5355 - currently in the USA
Serial number 5369 - currently in the UK
Chassis number 2030. A replaced output transformer, and a few components here and there, but otherwise all good. Pot codes "KM" and "AN", the latter being the later = January 1966.
Serial number 5371 - currently in the USA
Serial number 5372 - currently in Europe
A Foundation Bass set, shop plaque on top of the amplifier section - possibly "Musikhaus Hummel" in Frankfurt.
Serial number 5373 - currently in New Zealand
The chassis of this amp was made for a valve rectified amp, but the actual circuit, as built, is solid state rectified. The one visible date code on the mustard caps is A6N = first quarter of 1966. In view of the mustard caps and the mixed bag of resistors in the preamp, this amp is likely to have been made by Triumph, perhaps in 1966, but early 1967 is equally possible. Approaching the end of its contract with JMI in mid '67, Triumph built a number of amps to use up stocks of components.
Serial number 5380 - currently in the USA
Thanks to Mark for the pictures.
Serial number 5393 - currently in the USA
Chassis number 2141. In the preamp, Hunts caps with the date code "THS" = 42nd week of 1965 for their manufacture. Visible pots have "AN" = January 1966. Speakers in the cabinet have been renewed, the Midax horns removed some time ago. Thanks to Dan for the pictures.
Serial number 5396 - currently in the USA
Serial number 5403 - currently in the USA
Serial number 5404 - currently in the USA
Serial number 5435 - currently in the UK
Serial number 5439 - currently in Europe
A nice AC50 Super Twin amplifier and speaker cab set (no trolley). The original speaker and mains cables survive. Double pin corners on the speaker cab. Excellent cosmetic order; no shots of the electronics at present.
Serial number 5448 - currently in the UK
Chassis number 1736. Pot codes "EM", "JM", and "KM" = May, October and November 1965 - and for the Normal Channel volume "AN" = January 1966. The code of one of the blue Hunts capacitors is "TTS" = 44th week of 1965.
Serial number 5514 - currently in Europe
Chassis no. 1861. The brimistor is still in place. Pot codes "KM" = November 1965. Note the presence of the large green Hunts 0.1uf coupling caps in the preamp. The blue Hunts capacitors have the date code "TNS" = 47th week of 1965.
Serial number 5521 - currently in Switzerland
Chassis number 2193. Above, pics of the amp before restoration. In the power section, Hunts caps with the date code "TNS" = 47th week of 1965, and TCC caps with "XA" = January 1966. In the preamp, pots with "KL", "AN" and "BN", respectively November 1964, January and Febuary 1966. One of the green Hunts signal caps has "THS" = 42nd week of '65. Thanks to Ioannis for the pics.
Below, a couple of shots post restoration:
Serial number 5529 - currently in Europe
Two sets of pics, paired with an AC30 extension cab and a Foundation Bass cab. In the preamp, Mullard mustards with "C4N" and "D4N" = third and last quarters of 1964 for their manufacture. The pots have "AN" = January 1966.
Serial number 5532 - currently in Germany
Chassis no. 2197. Great condition. "28" chalked on the back panel and underside of the slider board. Thanks to Chris for the pictures. The blue Hunts cathode bypass capacitors in the preamp have the code "YTU" = 4th week of 1966.
NEW
Serial number 5522 - currently in Norway
Chassis number 1709. Exported to Scandinavia early on, the voltage selector removed (in accordance with local legislation) and the VOX hang-tag set in its place - a fairly common thing in these instances. Brimistor still in place. The gold-coloured TCC bypass caps in the preamp have the date code "WL" = December 1965 for their manufacture. A really nice amp. Thanks to Lasse for the pictures.
Serial number 5533 - currently in Europe
Chassis no. 2045. Pot codes are "AN" = January 1966. One of the green 4uf bias caps has the code "XA" = January 1966 (not 1965 as previously stated); and on of the blue Hunts caps has "TSS" = 45th week of 1965.
Serial number 5539 - currently in Europe
Serial number 5546 - currently in Spain
Two added Amphenol XLR sockets on the back panel (only one of which is wired in), and a jack socket. Below, some newer pictures of the exterior:
Serial number 5568 - currently in France
Paired with a solid state Foundation Bass speaker cabinet. Note the port bottom front. Amphenol XLR speaker sockets still present. The Amphenol mains socket has been removed.
Serial number 5590 - currently in Germany
Chassis number 2054(?). Brimistor and original Hunts capacitors still in place. In the preamp, WIMA capacitors and two pots with the date code "AN" = January 1966.
Serial number 5617 - currently in Europe
With two solid state Foundation Bass speaker cabinets, ports at bottom. Brimistor is still in place on the upper chassis. Amphenol XLR speaker sockets removed.
Serial number 5616 - currently in Germany
Sold in Germany in late 2020. Chassis number 2237. The pots have codes "CN" and "DN" = March and April 1966.
Serial number 5619 - currently in Germany
Superb condition. The amp still with its black and gold VOX hangtag. Accompanied by a Foundation Bass cab (and its original cover).
Chassis no. 1975. Pot codes "KM" and "AN" = November 1965 and January 1966. Not a thing changed or replaced. The blue Hunts cathode bypass capacitors in the preamp have the code "YIU" = 3rd week of 1966. Thanks to Heinz for the pics.
Serial number 5635 - currently in Europe
Serial number 5652 - currently in Europe
Chassis no. 2223. Accompanied by a later solid state Dynamic Bass cab. The green TCC cathode bypass caps in the preamp look to have the date code "XC" = March 1966.
Serial number in the 5000s - currently in the USA (?)
Chassis no. 2150. Plain metal shrouds to the transformers. In the preamp, Hunts and Wima capacitors.
FROM THIS POINT TRANSFORMERS ARE THE NEW BLACK TOPPED UNITS
These are often said to have been made by Albion. However, there is no evidence whatsoever for this ascription (which doubtless began as someone's guess). What is certain is that the new units were sourced by Burndept Electronics. The same maker made the transformers for the solid state range, also assembled at the West Street Works in Erith, which Vox shared with Burndept. The works were actually Burndept's.
Manufacturer's part numbers - Mains transformer: 66522. Output transformer: 66523. Choke: 66524.
Also from around this point one finds bulbous red Lemco capacitors in the preamp.
Serial number 5680 - currently in Germany
Note the black topped output transformer.
Serial number 5690 - currently in Europe
Cab and amp later sold separately. Note that the speakers have been replaced but the old Vox labels retained. The Midax horn remains.
Serial number 5692 - currently in the UK
Serial number 5693 - currently in Germany
Serial number 5716 - currently in Spain
The output transformer is one of the new black-topped units, the mains one of the earlier plain metal topped. The Foundation Bass cabinet is the original - note the "G-R" stamp inside - but refurbished with new grille cloth, logo and speaker.
Serial number 57xx - whereabouts unknown
Grille cloth of cab and amp faded to dark brown. Well used but still handsome.
Serial number 5726 - currently in the Netherlands (?)
Advertised for sale in the Netherlands (marktplaats.nl) in December 2012.
Serial number 5734 - currently in Europe
Serial number 5739 - currently in the USA
A superb example - complete with original cover. Chassis no. 2349.
Serial number 5744 - currently in Belgium
Chassis number 2351. One of the blue Hunts filter caps in the preamp shows part of its date code "UU" = 6th, 16th, or just possibly, 26th week of 1966. Thanks to Steev for the pictures.
Serial number 5753 - currently in Europe
Serial number 5754 - currently in Europe
Pictured with a later Vox Defiant speaker cabinet. New handles have been added to both amp and cab.
Serial number 5772 - currently in the UK
Thanks to Alan for the pictures. Note that the colour of the control panel has shifted - now a deep green.
Serial number 5784 - currently in the UK
Serial number 5799 - currently in the UK
Serial number 57xx - currently in the UK
Serial number 5800 - currently in the USA
Serial number 5815 - currently in Germany
NEW
Serial number 5834 - currently in Europe
Chassis number 2498. In the preamp, which is in good original order, WIMA and red Lemco signal capacitors. The pots have the date codes "CN" and "DN" = March and April 1966 for their manufacture. The case is now bare wood.
Serial number 5842 - currently in Germany
A nice AC50 with a Vox Sound Ltd (1970s) 2x15 cabinet.
Serial number 5843 - currently in Italy
Serial number 5847 - currently in Italy
Serial number 5890 - currently in the USA
Serial number 5900 - currently in Spain
Serial number 5921 - currently in the UK
Tolex and grille clothed removed, but otherwise in good condition.
Serial number 5929 - currently in the USA
In good cosmetic and electronic order. The brimistor is still in place. In the preamp, one of the blue Hunts cathode bypass caps has the date code "WAU" = 19th week of 1966.
Serial number 5941 - currently in Germany
A Foundation Bass set. Chassis number 2475. In the preamp, WIMA and red Lemco signal caps. The pots have "CN" date codes = March 1966 for their manufacture. The speaker - a later replacement (1974) - in the cab is a Fane Crescendo 18".
Serial number 5960 - currently in Italy
Serial number 5987 - currently in Europe
Chassis number 2473. Probably exported to Scandinavia early on - voltage selector removed and additional internal fuses supplied. In the preamp, WIMA and red Lemco signal caps. The pots have date codes "AN" and "CN" = January and March 1966 for their manufacture. The choke is stamped "ILB".
Serial number in the 5000s - currently in USA
Chassis no. 1824.
