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 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 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 5212 - currently in the UK
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 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 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 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 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 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 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.
Serial number 5533 - currently in Europe
Complete with its cab and cabs. A nice set.
Serial number 5568 - currently in France
Paired with a solid state Foundation Bass speaker cabinet. Note the port bottom front.
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 5619 - currently in Europe
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 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 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 refubished 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 5753 - currently in Europe
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 5799 - currently in the UK
Serial number 57xx - currently in the UK
Serial number 5800 - currently in the USA
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 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 5960 - currently in Italy
Serial number in the 5000s - currently in USA
Chassis no. 1824.