UPDATES

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January to May 2024

22nd May

Thanks to Simon, some new pictures of AC50 serial number 1004B. Further shots .

vox ac50 serial number 1004
vox ac50 serial number 1004

AC50 serial number 1004B.

11th May

Thanks to Dave, pictures of AC50 serial number 3128, along with a cab from a separate source, . It is probable that the amp was used by the MC5 at one time.

AC50 serial number 3128.

11th April

Thanks to John, further pictures of AC50 serial number 2086, correct sockets now fitted on the back panel, and the amplifier paired with a large-box speaker cabinet (carefully restored). The existing pictures of the amp, one of a small number issued relatively late on in a small box, can be found here.

2086
2086
2086
2086

AC50 serial number 2086.

10th March

Thanks to Dimitrios, pictures of AC50 serial number 6244 have been added .

6244
6244

AC50 serial number 6244.

19th February

Thanks to Glen, some shots of AC50 serial number 2612 - one of two amps with that number, this one with a hand-stamped serial number plate and presumably sent out from Dartford Road, the other with a machine-stamped plate and presumably sent out from the Vox Works at Erith. The amp pictured below is solid state rectified, the other 2612 is valve rectified.

In the first part of 1965, standard practice effectively went out of the window where AC50s and AC30 Super Twins were concerned. Amps were sent out from two locations, chassis evidently sat for longer on shelves, and machine-stamped serial number plates were clearly, at times, affixed on boxes well before any chassis had been allocated to them.

Normal practice at Dartford Road - certainly into 1964 - was to assign and stamp a serial number only after the amp had been made ready for sale and tested.

Solid state rectified. The latest visible date codes in the chassis are one of the pots with "AM" = January 1965, and a Mullard capacitor with "B5" = second quarter of 1965.

Hand-stamped serial number 2612.

Machine-stamped serial number 02612.

The replication of numbers has always seemed a distinct possibility. This however is the first concrete instance that has come to light. Others may of course follow.

18th February

Thanks to Ioannis, pictures of AC50 serial number 5521 . The latest component date code visible is from February 1966 (one of the pots). The earliest (also a pot) is from November 1964. Certain types/value of components could last a good while.

AC50 serial number 5521.

27th January

Entries for six AC50s with numbers in the 6000s : 6027, 6330, 6662, 6745, 6822, and 6908.

A new page coming on instances of large box AC50s as Public Address amplifiers. Below, an amp with a serial number in the high 3000s with a set of four Line Source 40 public address speaker cabinets - sold on Reverb a little while ago. The second escutcheon panel on the back panel may have been fitted at factory:

26th January

Entries for a further ten AC50s with serial numbers in the 5000s : 5172, 5206, 5216, 5228, 5278, 5439, 5754, 5834, 5929, and 5941.

25th January

Entries for four more AC50s with serial numbers in the 4000s : 4072, 4587, 4654, and 4795.

24th January

Entries for four more AC50s with serial numbers in the 3000s : 3196, 3611, 3666, and 3975.

23rd January

A couple more AC50s with serial numbers in the 2000s now added: and .

AC50 serial number 2187.

AC50 serial number 2858, paired with a Thomas Organ Buckingham speaker cabinet.

22nd January (2)

A note on the transformers used by Triumph Electronics for AC50s assembled from late 1963 to the end of 1964 - in other words for the AC50 Mark 1 (single channel amps with two, then four inputs) and for runs of the AC50 Mark 2 (two channel). So far as one can tell, the transformers all had printed paper labels pasted or sellotaped on. Mains transformers were designated "JMI M007A", output "JMI D008A", and choke "JMI X009A". Below, the label on the choke of AC50 serial number 1034. The labels on many mains and output transformers have since come away.

Serial number 1034, detail of choke.

It is not fully certain at present who added these labels: possibly the manufacturer, possibly Triumph, though the former seems most likely. If Triumph did add them - simply perhaps to keep things clearly identified in its stores - then one has to ask why the same sort of labelling was not added to the transformers of other models of amplifier assembled by the company for JMI.

Also to note that the mains and output transformers had part numbers stamped in black ink on their undersides. The output transformer of AC50 serial number 1015 (a Mark 1) has "714216", and the output transformers of AC50 serial numbers 1578, 1610, and 1723 (all Marks 2s) have "105736".

Serial number 1015, underside of output transformer.

Vestiges of a number can occasionally be spotted on the undersides of mains transformers, but heat for the most part has faded the ink to the point of illegibility. The six digit code makes one think in the first instance of the transformers used by Triumph for the range of PA amplifiers it had been contracted to assemble by JMI [ - transformers highly unlikely to have been supplied by Drake as previously mentioned - see now the , entry for 20th November 2025]. Alan Griffin remembers the sheet metal delivery lorry turning up (male employees were asked to break off from what they were doing to help unload), though unfortunately not the arrival of the transformers.

22nd January

Thanks to Ioannis, a shot of the chassis of AC50 serial number 5521, probably early 1966. The page on amps with numbers in the 5000s .

AC50 serial number 5521.

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