UPDATES

Older blog / update entries are now here.

2016 (September - December)

21st December (4)

A new page on AC50 trolleys now begun. These trolleys are fantastic pieces of design. Original early ones - ie. from 1964 - are very scarce.

21st December (3)

Chuck Botfield of the Rocking Berries, pictured in "Beat Instrumental" magazine, no. 28, August 1965. The amp: a small box thick-edged AC50 atop an AC30 cab (?) and trolley.

21st December (2)

Pics of the Dutch band "Influention" with a late AC50 - US-style logo - on top of a Super Foundation bass cab.

21st December

"4 Hits and a Miss" on stage, Terry Collier, the bassist, with a small box (thick edged) AC50 and Foundation Bass cab. Image .

20th December (2)

Talking of early trolleys with basket tops (rather than parallel bars), note the amp below, an AC30 super twin. The upright parallels above the pivot wheel are less widely spaced than in later trolleys.

20th December

The Ravens, a band formed originally by Robert Fripp in 1961, with an array of Vox equipment. Note the large-box AC50 in the foreground, sitting in the "basket" of an early trolley - much as the one used by "The Londoners" and Gene Vincent, below.

In late 1964, one regularly sees three Vox amps together - in promotional photos, on Top of the Pops (Yardbirds, Kinks, et al.), and other public events - an AC80/100, an AC50 super twin, and an AC50 Foundation Bass - probably nestling in the background of the pic. of The Ravens above.

Whether it was the same three amps every time is impossible to say - but these were the models that were readily made available by Vox whenever a camera was likely to be present.

18th December

The page on the Beatles' early AC50s now updated (long overdue). Further additions to appear soon.

Above, a new and better detail of the first known pic of the Beatles with their new AC50s, taken at one of the Christmas concerts at the Finsbury Park Astoria, 1963.

17th December (2)

The page on updated and augmented. The schematic of 1976 posted there too.

Herbie Goins and his band on stage in 1965 with a large box AC50. Photo from Alamy.

17th December (2)

A further diamond-input single channel AC50. Currently in Denmark. Corner protectors at front missing, but condition is generally excellent.

17th December

The introduction / introductory page now tidied up and now fitted out with better pictures. Around twelve further amps will be registered and illustrated over the coming days.

The greatest need is really for further and better images of early large box AC50s. If anyone has any, do send them in.

16th December

Pictures of .

10th December

New page begun on .

7th December

Early boxes, which were used sometimes randomly through to late 1964, have two vents in the baffle. Later boxes have solid fronts.

4th December

The page on early now revamped and updated. As with the page on small box twin channel amps, additions to follow.

A new page on .

3rd December

The page on small box twin channel AC50s now updated (long overdue). Further additions to follow. The AC50 parts list compiled by Thomas Organ is now on the (at foot).

Pictures of two early-ish large box amps added - one valve rectified and lacking its serial plate, the other , solid state rectified. Pictures also and info on . Thanks to Gerard for the latter.

1st December

Pages on particular classes of AC50 are being systematically tidied up: some have got pretty straggly.

29th November (2)

.

29th November

A further page from the Thomas Organ Vox service manual of 1967 - the JMI schematic (OS/054, undated) for the speaker connectors on the back panel of the Vox AC50. The schematics page will be updated later this week.

28th November

Three pages from the Thomas Organ Vox service manual of 1967. A parts list for the Vox AC50 and a copy of JMI schematic OS/075 for the add-on reverb unit, dated 15th Jan. 1965. A number of AC50s were fitted with this - see below, entry for 20th Nov.

The unit was of course originally designed for the Vox AC30 (note the references to the Vib. channel).

Click for a larger image. To enlarge further, click on the "expand" symbol that appears on the pop-up lower right. The same goes for the two images below.

27th November (2)

Fifty-two years ago last Sunday (20th Nov.), Gene Vincent and the Londoners played at the Empire Pool, Wembley. On stage: two AC80/100s (one in a thin-edged box), and a large-box AC50 in an early trolley with a basket top.

27th November

Serial number 1018B - single channel, thin edged box - now known to survive. Pictures to follow.

Further pages to be updated over the course of this coming week.

20th November

The site is in the process of being updated. All pages should still be accessible - but do let me know if anything has temporarily dropped out.

Above, serial number 4018, solid state rectified, no brimistor = mid 1965. Note the reverb unit fitted on the shelf. Several of these AC50s survive.

13th November (3)

Another Werth Surgistor:

A detail from AC50 serial number 4282 showing the position of the surgistor - as in a second amp pictured lower down on this page (entry 5th Nov.).

Neither amp originally had a brimistor. Clearly when they were taken in for servicing, possibly to the same Thomas Vox repair centre, the instruction evidently was to follow the latest schematic (which included a brimistor). Since brimistors were not to hand, a US-made Werth surgistor was fitted instead - not exactly safely - the body of the surgistor is millimeters away from the lip of the preamp overhang, not to mention, if knocked, the terminals of the voltage selector.

Addendum: surgistors are also to be seen in serial nos 5260 and 5404.

13th November (2)

There are at present something in the region of 300 large box AC50s registered and pictured on this site. But to put that in context, around 4% of the total number produced.

13th November

Large box AC50s for the American market:

In order to conform to US regulations, AC50s, T60s and AC100s destined for export were fitted by JMI with an extra capacitor over the mains switch - a "snubber capacitor".

The capacitor was 0.01uf 500v, grey polythene, made by Radiospares. In AC50s it was held vertically to the chassis by a bracket next to the HT fuse and choke.

Clearly the available pics of some amps are not revealing (ie. the preamp is not shown). But where we are able to tell, these caps (or sometimes just the bracket) remain in place in serial numbers 1999 (made by Triumph), 2984, 3014, 3384, 3615, 3680, 4018, 4083, 4095, 4282, 5260, 5360, 5432, and 6032. The pic. below is of no. 2984.

The capacitor is not marked on any known schematic. It should be said of course that a good number of amps currently in the US did not find their way over straight from the factory (even early on).

Above, a shot showing the position of the capacitor in a T60. As with the AC50 and AC100, it is not marked or specified in any known schematic.

6th November (3)

Two strange ones, pictured with two late AC100s. The AC50 boxes are visibly smaller but have early-style back panels with Amphenol connectors. The amps inside are both solid state rectified, one without a brimistor (serial no. in the 3000s), one with (serial no. in the 4000s) - the former mid 1965 and the latter probably early 1966.

Hard to say for certain, but the boxes look original. Note that one has rounded corners at back, the other square. The back panels themselves are almost certainly later repros, however, mimicking early ones to look "Beatley" - but with anachronistic Amphenol connectors and red warning plaques.

6th November (2)

Serial number 1506 - small box, brown front, twin channel. These late small box amps were produced by Triumph side by side with the newer large box units (also with brown grille cloth).

And alongside these small and large box AC50s, Vox/Triumph seems to have continued making copper panelled, single channel, diamond input amps.

<

Above, serial number 1532 - original black cloth on both cab and amp - single channel, diamond inputs - . Note, however, that Triumph-made amps do not have sequential serial numbers - ie. serial number 1532 is highly unlikely to be separated from 1506 by twenty-five other amps. Indeed, 1532 could be earlier than 1506, though given the black grille cloth, not by much.

6th November

Serial no. 7722, added on this page. With the advent of the one-piece US-style logo, which comes in at around serial number 7400, we are in the solid state era - 1967.

The JMI pricelist from April 1967 (post Queen's Award for Industry). AC50s for guitar and bass still available, along with the AC100 and the new solid state line. To judge from survivals however, AC50s for bass seem to have been the most popular of the two options.

Pictures of serial , and .

5th November

An early solid state rectified (non-brimistor) AC50 that popped up on ebay in the summer of 2016, baffle and back board absent. Probably from late summer 1965. Chassis number 934. Pot codes "GM" = June 1965.

Two things of particular note - the preamp valves branded "VOX" and with Thomas Organ part numbers, and the presence of a Werth Surgistor (a sort of brimistor surrogate) under the lip of the preamp by the voltage selector - bottom right hand picture of the four above, far right.

The amp was clearly serviced at some point in the later 1960s at a Thomas Organ Vox service centre and fitted with a surgistor-brimistor in accordance with the latest AC50 schematic.

The same seller (in Kansas) also had an AC100 "100W Amplifier" (early fixed bias, no brimistor), produced in the late summer of 1965. That amp had a Werth Surgistor fitted later too. It may be that the two amps were purchased at the same time and serviced at the same time a few years later.

This entry has also been posted .

AC100 serial number in the low 500s, currently in the UK. The amp came with a Thomas Organ service parts list, and set of schematics, one unrecorded elsewhere.

26th September

A small-box thick-edged amp in charcoal tolex now in Brighton.

4th September and 7th September

7th: Sept: dating of the amp in the thin-edged box (pictured below) now corrected.

Serial no. 3103 (solid state rectified, no brimistor) recently found in Appleton, Wisconsin.

Pictures of serial no. 4852 .

Pictures of serial no. 1999, valve rectified, dome voltage selector

.

Below, a grey panel AC50 from mid 1965 (solid state rectified, no brimistor) in a thin-edged box (from 1964). A single speaker connector on the back panel. Note that the panel has rounded corners - very unusual. The box however looks to have been made originally to take a square-cornered panel.

A clip of an early small-box AC50 (?) - or a standard amp in a repro small box (?) - no further details at present though.