THE EARLIEST FIXED BIAS AC100s - 1965

The "100W Amplifier"

Black transformers, but no brimistor - late summer 1965

100 Watt Amp Schematic

Dated 30th May 1965.

Around two hundred and ninety "100W Amplifiers" were made at the Burndept works in Erith in June/July of '65, large numbers of which were shipped to the Thomas Organ Co. for distribution in the USA - mostly in air shipments. A small proportion of amps were retained, however, by JMI for sale in the UK and Europe. Most of the amps sent to the USA seem to have accompanied 4x12" cabs - ie. the AC100 SDL.

A schematic was included by Thomas Organ in its repair dossiers, along with a parts list and schematics of the cathode biased AC80/100 and the newer AC100 Mark 2 (the AC100/2 with brimistor) - .

The fixed bias amps ran much much cooler than the AC80/100s, even if the bias was well on the low side for the EL34s. A true 100W was achieved.

early fixed bias ac100, mains transformer
  • early fixed bias ac100, mains transformer
  • serial number in the 500s, chassis front
  • serial number in the 600s (03), chassis top

More of a note than anything: four chassis survive with long triangles of purple/russet sticky tape behind the mains transformer. Chassis nos 11xx, 1201, 1237 and 1384.

Amps in the early 500s (also 498) have no white warning plaques. These come in again around serial number 540. Circular Amphenol XlR speaker sockets were introduced around serial number 580. Prior to that one finds rectangular Cannons.

The transformers, which were sourced by the Vox / Burndept Works, have black shrouds. From the second batch on, the part numbers were stamped on the undersides of both. These units were certainly not made by Albion as is often said or implied. Although firm evidence is lacking at present, Woden seems likely. Vox used the same manufacturer later on to provide the transformers for its solid state range of amps (the Conqueror, Defiant and Supreme, and so on).

Below, a Thomas Organ "Vox Service Flash", dated 11th October, 1965, relating to the fitting of a surgistor - a sort of thermistor/brimistor (made by the Würth [Wuerth] company) - to AC100s, the idea being to give a "soft start" to the amp. To judge from what is said, the surgistor was added before the AC100s were sent to dealers. Replacement capacitors were invariably Spragues. The amps in view were for the most part the ones JMI built to the "100W Amplifier" circuit diagram - ie. no brimistor, pre-AC100 mark 2. Surgistors were also fitted to certain AC50s.

Vox AC100 surgistor - Thomas Organ Vox Service Flash, October 1965

Dated 101165 at foot. Note that the AC100 is still referred to as the "Super Beatle". Thanks to Martin Kelly for the picture.

Below, a picture of a surgistor fitted to an amp with a serial number in the 500s between the voltage selector and the transformer (the position selected by Thomas Organ). Underneath, a shot of the shadow left by one that went up in smoke (in serial number 520).

Wurth (Wuerth) Surgistor in Vox AC100 with a serial number in the 500s

AC100 ("100W Amplifier") serial number in the 500s.

Surgistor once added to Vox AC100 serial number 520

AC100 ("100W Amplifier") serial number 520. The shadow of a blown surgistor at left, the wiring put back to normal, but the nut used to secure the surgistor not returned to the voltage selector.

Also to note that JMI modified amplifiers destined for the USA by adding a 0.05uf Radiospares capacitor at the main fuse (as Fender did) to suppress arcing and radio frequency interference.

The Who, Copenhagen 1965

Repeated from the , The Who in Copenhagen, 25 September 1965, with six AC100s. The amps are most likely the new fixed bias "100W Amplifier" - one can tell they are not cathode biased by the presence of two screws along the top edge of the backboard. Cathode biased amps had only one.

Surviving amps

Serial number unknown (chassis number 11xx) - currently in the USA (owned by "plexi69")

  • early fixed bias ac100, front
  • Vox AC100 early fixed bias ac100, back
  • Vox AC100 early fixed bias ac100, top
  • Vox AC100 early fixed bias ac100, chassis top
  • early fixed bias ac100, preamp right
  • early fixed bias ac100, preamp left
  • early fixed bias ac100, preamp centre
  • early fixed bias ac100, chassis bottom
  • early fixed bias ac100, chassis underside left
  • early fixed bias ac100, chassis underside centre
  • early fixed bias ac100, chassis underside right
  • early fixed bias ac100, mains transformer

Probably one of the earliest "100W amplifiers" surviving. The serial plate is gone but the chassis number is 11xx, which suggests closeness in terms of date to the latest cathode bias amps . The latest of those, in terms of chassis number, is 1145. Transformers are the new black units, there is no brimistor (and no holes on the chassis for the stand-offs required), resistors are by and large the white carbon composites ("carbon comps") made by Erie. Electrolytic capacitors are or were TCCs, and the capacitors in the signal path (in the preamp) are gold WIMA tropyfoils.

The grey 0.05mfd Radiospares capacitor behind the mains switch indicates that the amp was produced for export to the USA.

On the underside - the last four pictures - note the large (2W) plate resistors on the left of the board, laid out at 90 degrees to the other components, and the fixed bias network in the centre of the board. Two new dark brown resistors stand in place of the zener diodes specified in the schematic. The long 18K "bleeder" (voltage divider) resistor has the date code "WA" = January 1965. The wiring of the output valve bases has also been adjusted to accommodate new resistors (the square white ones) that serve to drop the screen voltage slightly. A great amp.

NEW

Serial number in the 400s - currently in the USA

Chassis number 1163. An early fixed bias "100W Amplifier". Mains transformer renewed. As serial number 496 below, the back panel originally had an Amphenol mains socket and Cannon XLR. Bought in Ann Arbor in 1976/1977 and used for many years in the band "Choker". Thanks to Devin for the pictures.

Serial number 496 - currently in the USA

  • serial number 496
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  • serial number 496

Serial number 496 with a repro trolley and cab. The amp has been brought back to working order with new transformers (output and mains) and new caps. The choke probably comes from a different Vox amp. At this point (see above and below), they are normally gold coloured and marked only with the part number "66429". The one now in the amp is a Woden "76854". Thanks to Marc for recent (the last two) pictures.

Serial number 498 - currently in the USA

A few replaced components (fuse, mains socket), but otherwise in good condition. The preamp filter caps are now Spragues. The amp was sold on Reverb (August 2018).

Serial number 502 - currently in the USA

  • serial number 502, cab and amp
  • serial number 502, midax horn
  • serial number 502, crossover capacitor
  • serial number 502, Cannon XLR
  • serial number 502, chassis top
  • serial number 502, control panel left
  • serial number 502, control panel centre
  • serial number 502, control panel right
  • serial number 502, chassis underside
  • serial number 502, chassis underside left
  • serial number 502, chassis underside, valve socket
  • serial number 502, preamp left
  • serial number 502, preamp right
  • serial number 502, bass pot
  • serial number 502, preamp valve socket
  • serial number 502, volume and treble pots
  • serial number 502, grid resistors
  • serial number 502, preamp cathode bypass capacitors
  • serial number 502, output terminal block
  • serial number 502, Burndept chassis number
  • serial number 502, preamp valve
  • serial number 502, choke
  • serial number 502, serial number plate
  • serial number 502, back panel, Cannon XLR

Chassis no. 1207, serial plate no. 502. Amp and cab have been together since 1967, and probably left the Vox factory together July-ish 1965. One can see in the pictures of the amp above that one of the pots has the stamped code "DM" = April 1965, and that two of the TCC capacitors have codes "WB" and "WD", respectively February and April 65. Both are in fine condition. Note for instance the original wiring and stapling in the speaker cabinet, and the intactness of the preamp. This amp had no brimistor. The single hole (by the choke) is new. As in the case of the amp with chassis 11xx (above on this page), the choke has the code "66429", doubtless having been supplied by the company that made the black-shrouded mains and output transformers, which are later bear the numbers "66775" and "66776". One of the earliest original amp and cab sets surviving.

From this point the black-shrouded transformers have code numbers stamped on their underside (66775 for the mains, and 66776 for the output)

Serial number low 500s (serial plate not original to this amp) - currently in the USA

  • serial number in the 500s, front
  • serial number in the 500s, top
  • serial number in the 500s, top
  • serial number in the 500s, back
  • serial number in the 500s, back close
  • serial number in the 500s, serial number plate
  • serial number in the 500s, serial number plate
  • serial number in the 500s, control panel centre
  • serial number in the 500s, control panel left
  • serial number in the 500s, control panel right
  • serial number in the 500s, preamp
  • serial number in the 500s, preamp left
  • serial number in the 500s, preamp centre
  • serial number in the 500s, preamp right
  • serial number in the 500s, Burndept chassis number
  • serial number in the 500s, chassis front
  • serial number in the 500s, replaced choke
  • serial number in the 500s, mains transformer
  • serial number in the 500s, output transformer
  • serial number in the 500s, EL34s
  • serial number in the 500s, preamp valves
  • serial number in the 500s, preamp valves
  • serial number in the 500s, chassis bottom
  • serial number in the 500s, chassis underside right
  • serial number in the 500s, chassis underside right
  • serial number in the 500s, chassis underside centre
  • serial number in the 500s, chassis underside left
  • serial number in the 500s, chassis underside left, detail
  • serial number in the 500s, mains transformer underside
  • serial number in the 500s, rectifier diodes
  • serial number in the 500s, box underside
  • serial number in the 500s, box underside, grille
  • serial number in the 500s, box underside, grille
  • serial number in the 500s, box underside, grille
  • serial number in the 500s, back panel right
  • serial number in the 500s, back panel left

Chassis number 1237. This was originally a fixed bias AC100 - black shrouded transformers, "flying" 330K grid resistors in the preamp (among other signs of fixed bias arrangement), and a chassis number consonant with a serial number in the lowish 500s. At some stage, probably in the 1990s, the power section of the amp was converted to cathode bias. Despite the changes, a very nice amp. The box is likely to be original to the amp - note the two fixing points along the top edge of the back board. The box of an amp with a serial number in the 500s would only have had one.

Serial number low 500s - currently in the USA

  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s
  • serial number in the low 500s

Chassis number 01242, original serial number plate missing. At some point (in the 1970s?), four further holes for inputs were provided, probably with a view to converting the amp to PA purposes. Nothing futher seems to have been done. The transformers are missing their outer wrapping so it is not possible to say whether part numbers were stamped on or not. The original 2W Erie plate resistors are still in place. In the preamp, the green TCC filter caps have the date code "WD" = April 1965. The Amperex 12AX7 (ECC83) has the date code "B5K3" = 3rd week of November 1965 - an early replacement for an original Mullard damaged in transit? Thanks to Michael for the pictures.

Serial number 520 - currently in the UK

  • serial number 520
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  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520

Chassis number 1201. A few replaced caps in the preamp, and some new zener diodes in the power section, but otherwise good. The manufacturer's code 66775 is stamped on the underside of the mains transformer. The output transformer is unstamped. As in a number of early fixed bias amps, the feeds from the output transformer are curled round the edge of the chassis rather than being passed through the hole in the preamp. Note the Mullard BY100 ("top hat") rectifier in the bias circuit. Both XLR and mains connector have been replaced on the back panel. The screw holes that remain indicate that the speaker output, certainly, was a rectangular XLR. Further inspection will reveal whether the mains connector was an Amphenol (held by three screws) or a rectangular Cannon LNE-11 (held by two). The cover, without a legend, is original.

  • serial number 520
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  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
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  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520
  • serial number 520

A Cannon XLR speaker connector installed. Removing the IEC connector showed that an Amphenol was originally there (a replacement now fitted). The pots have the code "DM" = April 1965; and the Daly filter capacitor "WD" = April 1965 too. Note the suppressor cap (Radiospares) for the mains switch, visible behind the panel fuseholder - installed by Vox in amps intended for the US market.

Serial number 526 - currently in the USA

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  • serial number 526
  • serial number 526

Chassis number 1236. Two XLR speaker connectors on the back panel: one a rectangular Cannon, the other an Amphenol. Remaining screw holes show that the mains connector was an Amphenol.

Serial number unknown - currently in the UK

  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
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  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s

Chassis number 1204. The Amphenol mains connector remains. Possibly originally two Cannon XLR speaker connectors; only one remains. The preamp is intact. Mains transformer is original, though its top cover has been removed. The output transformer may be from a later AC100 (to be determined), as there are solder tags on its underside rather than flying leads. Date code the original filter cap. is "WD" = April 1965.

serial number low 500s

The remaining original Mullard yellow-print EL34 has the code "B5D4" = Blackburn Factory, 1965, last week of April. The other three valves are General Electric branded Mullards.

  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s
  • serial number low 500s

Pics shortly after the arrival of the amp in the UK. Note the Werth "Surgistor" under the lip of the control panel by the voltage selector. The amp seems to have been repaired at a Thomas Organ repair shop, where a replacement slightly later AC100 output transformer was added, and some new components here and there. The shroud was taken off the mains transformer. Very probably the repairman followed the AC100 Mk2 schematic (rather than that of the "100W Amplifier"), supplying the surgistor as a stand-in for a brimistor. An AC50 has also been spotted (thanks to Tom for the info) with a Werth Surgistor added in the same position.

Additional note: the treble and bass pots (1M) have the date codes "DM" = April 1965. See the pic above. The volume pot (500K), which turned out to be defective and had to be removed, has the code "AM" = January 1965. Picture below.

serial number low 500s

Serial number 531 - currently in the UK

  • serial number 531, front
  • serial number 531, top
  • serial number 531, back
  • serial number 531, Amphenol power connector
  • serial number 531, serial number plate
  • serial number 531, Cannon speaker XLR
  • serial number 531, box side
  • serial number 531, box side
  • serial number 531, handle
  • serial number 531, chassis front
  • serial number 531, current output valves
  • serial number 531, chassis edge
  • serial number 531, chassis no valves
  • serial number 531, chassis and choke
  • serial number 531, chassis right
  • serial number 531, control panel left
  • serial number 531, control panel centre
  • serial number 531, control panel right
  • serial number 531, Burndept chassis number
  • serial number 531, preamp
  • serial number 531, preamp left
  • serial number 531, preamp centre
  • serial number 531, preamp left
  • serial number 531, grid resistors
  • serial number 531, chassis fuseholder
  • serial number 531, input jacks
  • serial number 531, bass pot
  • serial number 531, treble and bass pots
  • serial number 531, chassis underside right
  • serial number 531, plate resistors
  • serial number 531, rectifier diodes
  • serial number 531, bias circuit
  • serial number 531, underside tag board
  • serial number 531, EL34 sockets
  • serial number 531, EL34 sockets
  • serial number 531, Amphenol power connector
  • serial number 531, output valve sockets
  • serial number 531, original output valves
  • serial number 531, original output valves, detail
  • serial number 531, original output valves, detail
  • serial number 531, original output valves, detail
  • serial number 531, original output valves, detail

Chassis no. 1219. Serial no. 531. Another early "100W amplifier", ie. without a brimistor (note the absence of holes in the chassis for the standoffs). Evidently close in terms of components and arrangement to the amps above - note for instance the choke, and the large grey/blue Radio Spares paper capacitor across the power tagboard on the underside of the chassis, which has been treated (zinc passivated), a practice later dropped.

Three matching yellow-print Mullard EL34s came with the amp, all XF2s - the latest date code is "B5E5" - last week of May 1965. The code of the non-matching GE valve is "B5H6" - August 1965, which probably indicates that an EL34 blew fairly early on and was replaced in late '65. Date codes of the original capacitors that remain are "VK" and "WD", respectively December 1964 and April 1965. The amp probably left the factory in June/July of that year.

White warning plaque reintroduced

Serial number 532 - currently in the USA

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  • serial number 532

Sold on Reverb, October 2020. The preamp and power section converted in recent years to the AC80/100 circuit. The output and mains transformers were replaced at some point. The choke, which is original (part code "66429"), is stamped in white, as in the case of that of serial number 531 (above), with the date code "GTB". Pictures to follow.

Serial number 542 - currently in the UK

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Chassis no. 1153.

Updated/revised: This amp is likely actually to have been exported to the USA (rather than simply made for export but retained for sale in the UK as suggested previously) - note (i) the presence of the large Radiospares suppressor capacitor in the preamp by the mains switch, and (ii) underneath the voltage selector, the Werth Surgistor, fitted to certain amps by Thomas Organ in order to bring them into line with the Mark 2 schematic. The surgistor is effectively a surrogate for the brimistor.

A few replacement components here and there - capacitors, plate resistors, mains switch, and one pot - but otherwise not much changed. The mains transformer has the part-code stamped on its underside but not the output. Thanks to Robert for the pictures.

Serial number 553 - currently in the USA

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A paisley ensemble - serial no. 553 with one open-backed and one closed-backed Super Beatle cab. Chassis no. 1230. The amp has its original cover (without a VOX logo, as in the case of serial number 520).

  • serial number 553
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Thanks to Brian for the pics.

Serial number 570 - currently in the USA

No pictures available at present: grey panel, existence reported on a "VoxTalks" (old bulletin board) thread.

Serial number 584 - currently in the USA (collection: Andy Sandler)

  • serial number 584
  • serial number 584
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  • serial number 584

In the left hand picture, serial number 584 sitting on a 2 x 15" bass cab. Second from left, with its original 4 x 12 cab - a fine thing. Second from right, a back view, showing inputs and white warning plaque. Far right, AC100 number 854, also with its original 4 x 12" cab.

Serial number 587 - currently in the USA

  • serial number 587
  • serial number 587

Good condition. Original transformers in place. Control knobs changed, and a standby switch added, but otherwise all good. Thanks to Gary for the pics.

Serial number in the 500s - currently in Italy

  • serial number in the higher 500s
  • serial number in the higher 500s
  • serial number in the higher 500s

Serial number said to be in the 500s. The presence of the white warning plaque indicates it is post no. 540. The bias circuit has been restored. In good all round order.

Serial number in the 639 - currently in the USA

Mains transformer replaced with a unit made by Douglas Transformers (Louth, UK). Probably added at the same time - 1970s? - a new set of filter capacitors (two pairs, made by Radiospares, along the lines set out in the AC100 circuit diagram of 1967). The amp evidently found its way to the USA, where it currently is, well after the 1960s. Some replaced capacitors in the preamp, but otherwise that is in good order. One of the 25uf cathode bypass caps has the date code "WD" = April 1965. The Woden choke has the code "EW" = May 1965.

Serial number in the 600s? - currently in the USA

  • serial number in the 600s (01), front
  • serial number in the 600s (01), back
  • serial number in the 600s (01), amp
  • serial number in the 600s (01), amp top
  • serial number in the 600s (01), serial number plate

Advertised on Gbase in late 2009 / early 2010. Inverting the mandatory blurry picture of the serial number plate in Photoshop seems to give 6xx. Some sort of standby circuit was installed by the owner (fairly easily achieved unobtrusively) - a sensible precaution as this, if memory serves, was someone's gigging amp. The cabinet is later - note the double-pin corners, the hole for the pivot wheel high up on the side, and the tell-tale yellow paint on the screws inside. Judging by their orientation, the speakers have terminals in between the struts of the frame - therefore post-1966. In view of the yellow paint and the position of the pivot point, the cabinet is either a JMI or "Vox Sound Equipment Limited" Supreme cab retro-fitted to look like an AC100. Handles have been let in the sides.

Serial number in the 600s? - currently in the USA

  • serial number in the 600s (05), front
  • serial number in the 600s (05), back
  • serial number in the 600s (05), top

The two screws on the top edge of the back panel indicate a fixed bias amplifier; and the white warning plaque one somewhere in the 440 - 730 range. The round amphenol mains connector remains, but the speaker XLRs have been replaced.

Serial number in the 600s? - currently in Italy

  • serial number in the 600s (04), front
  • serial number in the 600s (04), front close
  • serial number in the 600s (04), side of 2x15 cab
  • serial number in the 600s (04), back
  • serial number in the 600s (04), top of amp
  • serial number in the 600s (04), control panel
  • serial number in the 600s (04), control panel, right

A nice bass rig. No serial number plate, but a white plaque, so as above, somewhere between c. 440 - 730. Back panel connectors replaced, but all else looks good.

Serial number in 600s - currently in Italy

  • serial number in the 600s (07), front
  • serial number in the 600s (07), front
  • serial number in the 600s (07), front
  • serial number in the 600s (07), front
  • serial number in the 600s (07), front

White warning plaque and two-line serial number plate. Certainly a fixed bias amp - the box has two screws on the top edge of its backboard. Its position here, among amps with numbers in the 600s, is arbitrary for the time being.

Serial number 660 - currently in South Africa

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Sold on an auction site in South Africa in 2014.

Serial number 663 - currently in Japan

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Serial number 671 - plate, warning plaque and one 18 inch speaker only, currently in France

  • serial number 671, serial number plate
  • serial number 671, bass bin front
  • serial number 671, bass bin side
  • serial number 671, bass bin side
  • serial number 671, bass bin grille
  • serial number 671, bass bin horn
  • serial number 671, bass bin jack sockets
  • serial number 671, bass bin interior
  • serial number 671, bass bin horn
  • serial number 671, bass bin horn
  • serial number 671, bass bin 18 inch Celestion driver
  • serial number 671, bass bin 18 inch Celestion driver
  • serial number 671, bass bin crossover

The strange remants of AC100 serial no. 671 - just the serial number plate, warning plaque and one 18 inch speaker, presumably from a Foundation Bass cabinet - therefore a bass amp - entombed in an odd, though rather handsome, PA-style cabinet. The amp, according to the owner, is long gone.

Serial number 682 - currently in Hungary

  • Vox AC100 serial number 682
  • Vox AC100 serial number 682
  • Vox AC100 serial number 682

Probably produced in July 1965. In excellent condition. Thanks to Csaba for the pictures.

Serial number 683 - currently in Europe

Vox AC100 serial number 683

Serial numbers 683 and 1064 - - were both owned at one time by a collector in Germany. His numbered stickers can be seen on the serial number plates. Both amps are paired with Supreme cabs from early 1968 - to emulate SDLs.

Serial number 686 - currently in the USA

  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686
  • Vox AC100 serial number 686

Sold on Reverb, 2017. The speaker cab may be the original but adjusted - the horn cut-outs in the baffle have been enlarged, the back is new, and there are replacement US speakers in the upper compartment. The amp itself looks in good order - few changes. No component date codes are visible. The labels on the back, added in the US, are interesting. No mention of JMI / Thomas Organ though.

NEW

Serial number in the high 600s? - currently in Ireland

Chassis no. 1268. Built in line with the "100W Amplifier" circuit, but at least two unusual later elements. A superb set of pictures .

Serial number 688 - currently in the USA

Pictures only of the exterior. The back panel has new hardware (sockets and added supporting panels). On the control panel, a new fuse-holder is visible.

Serial number 691 - currently in the USA

No details at this point.

Serial number in the high 600s / low 700s - currently in the UK

  • Vox AC100 serial number in the 600s (02), front
  • Vox AC100 serial number in the 600s (02), top
  • serial number in the 600s (02), top
  • serial number in the 600s (02), back
  • Vox AC100 serial number in the 600s (02), preamp
  • serial number in the 600s (02), control panel
  • serial number in the 600s (02), chassis top
  • serial number in the 600s (02), chassis, output valves
  • serial number in the 600s (02), Burndept chassis number
  • serial number in the 600s (02), chassis underside
  • serial number in the 600s (02), chassis underside centre
  • serial number in the 600s (02), chassis underside left
  • serial number in the 600s (02), chassis underside right
  • serial number in the 600s (02), chassis underside, valve socket

Chassis number 1348, so probably a serial number in the high 600s, perhaps low 700s. No brimistor. Note that the Vox logo is composed of separate letters "V O X". One of the three original filter capacitors in the preamp has the code "VL" = November 1964, a while therefore before this amp was built; another has "WA" = January 1965. The 470ohm resistor on the output block has the code "WD" = April 1965; and the choke has the code "EW" = May 1965. May 1965 is also the date of one of the original Mullard yellow-print ECC82s (the other dates from late '64). The back board is a replacement. The output transformer is the original turned sideways - and has the code stamped in white on the side - see the pictures below. Inside the box, the white stencil inside of the Gla-Rev company ("G-R"), which made cabinets under contract for JMI.

serial number in the 600s

The stencil of Gla-Rev, manufacturer of cabinets for JMI.

  • serial number in the 600s (02), front
  • serial number in the 600s (02), front grille, logo
  • serial number in the 600s (02), box top
  • serial number in the 600s (02), chassis top
  • serial number in the 600s (02), choke
  • serial number in the 600s (02), output transformer, side
  • serial number in the 600s (02), chassis front
  • serial number in the 600s (02), chassis underside right
  • serial number in the 600s (02), preamp
  • serial number in the 600s (02), preamp left
  • serial number in the 600s (02), preamp right

Now restored to full working order with (as far as possible) new old stock components.

Serial number in the high 600s / low 700s - currently in the USA

  • serial number in the 600s (03), front
  • serial number in the 600s (03), front
  • serial number in the 600s (03), top
  • serial number in the 600s (03), top detail
  • serial number in the 600s (03), back
  • serial number in the 600s (03), control panel left
  • serial number in the 600s (03), control panel right
  • serial number in the 600s (03), box underside
  • serial number in the 600s (03), chassis top
  • serial number in the 600s (03), chassis underside
  • serial number in the 600s (03), choke
  • serial number in the 600s (03), preamp
  • serial number in the 600s (03), preamp
  • serial number in the 600s (03), Burndept chassis number
  • serial number in the 600s (03), Burndept chassis number
  • serial number in the 600s (03), preamp left
  • serial number in the 600s (03), preamp right
  • serial number in the 600s (03), preamp right

Chassis number 1384. Sold on ebay in July 2011, and offered again a couple of months later (with new pictures). Nice cosmetic condition. Changes: a replaced mains transformer (and nicely rewired power section), a new fuseholder, some renewed components in the preamp, and the provision of a switch (for changing impedance?) on the back board by the speaker output socket. Although holes are present in the upper chassis, there is no brimistor - the holes in any case are not in the right positions - see below. Note that the warning plaque on the back board is still white.

Serial number in the high 600s / low 700s - currently in the USA

  • serial number in the 700s (01), chassis front
  • serial number in the 700s (01), chassis top
  • serial number in the 700s (01), choke
  • serial number in the 700s (01), output valves
  • serial number in the 700s (01), chassis from side
  • serial number in the 700s (01), chassis from side
  • serial number in the 700s (01), preamp

Chassis no. 14xx. No brimistor. The code on the Woden choke is "EW" = May 1965. The amp has been nicely restored. Its black control plate is from another amp - the original (grey) is in the UK, having been sold on ebay. The box and its back panel fittings were all acquired separately.

Serial number in the 700s - currently in Japan?

serial number in the 700s (02), chassis

A single image, originally posted on the . The text says no brimistor. Note the small tagboard in the preamp for the 330K grid resistors, the large grey Radio Spares 0.22uf in the bias network (underside of amp), the original 1W Erie plate resistors and green TCC caps. The black-shrouded transformers appear to have no stamped numbers on their undersides. XLR sockets for power and speaker.

Serial number 708 or 709 - currently in Japan

  • serial number 708, chassis front
  • serial number 708, chassis front
  • serial number 708, chassis front

Box recovered with smooth charcoal tolex, brown replacement grille cloth, corner protectors not put back on; the amp has been given a link voltage selector and copper control panel to make it look earlier. In pictures of the exterior, one can see the amp's true nature - "100W Amplifier", late summer 1965 - the serial number (standard machine stamped), small 19H choke visible through the top grille, Amphenol connector on the back panel, and solid red indicator lamp on the control panel.

Serial number 719 - currently in Russia

Below, older pictures

  • serial number in the 600s (06), front
  • serial number in the 600s (06), front
  • serial number in the 600s (06), front
  • serial number in the 600s (06), front
  • serial number in the 600s (06), front
  • serial number in the 600s (06), front
  • serial number in the 600s (06), front

Close to the end of the run of "100W Amplifiers". Note the plain metal fixings for the handle, and the presence of Amphenol connectors for both mains and XLR. Excellent condition.

Serial number 724 - currently in the UK

  • serial number 724, front
  • serial number 724, front
  • serial number 724, top
  • serial number 724, back
  • serial number 724, top
  • serial number 724, back panel
  • serial number 724, serial number plate
  • serial number 724, preamp
  • serial number 724, front
  • serial number 724, chassis top
  • serial number 724, chassis front
  • serial number 724, chassis, output transformer
  • serial number 724, back panel
  • serial number 724, serial number plate
  • serial number 724, Burndept chassis number
  • serial number 724, preamp left
  • serial number 724, preamp centre
  • serial number 724, preamp right
  • serial number 724, control pots
  • serial number 724, volume pot
  • serial number 724, chassis underside
  • serial number 724, chassis underside, power section
  • serial number 724, chassis underside, power section

Chassis no. 1303. New mains socket, but still the original XLR speaker connector. An impedance switch fitted on the back panel. The warning plaque is still white. Note that the new style red plaque had come in by serial no. 748.

A bit of a tangle in the power section - main filter caps have been replaced by pairs of axial caps in parallel. The output transformer is an old replacement. The choke has the code "EW" = May 1965. The preamp is fairly intact.

Pot codes - see below - "EM" = May 1965. Photos of the codes photographed using a a mirror have been reversed (ie. put the right way round) in Photoshop.

New photos - Sept. 2014

  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front
  • serial number 724, front

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