Early AC100 mark 2s

Amps conforming to the "AC 100/2" schematic - from August 1965

In the late autumn of 1965 Vox introduced the AC100 mark 2. Its circuit followed that of the "100W Amplifier" produced in the summer of that year - on which - but incorporated a brimistor, a temperature dependent resistor, designed to slow the inrush current when the amp was first switched on.

Details on the brimistor . The name elides that of "Brimar" (the manufacturer) and "resistor".

The brimistor sits in the circuit diagram above between the rectifier diodes and choke and filter capacitor network, upper right. "CZ4" is the type.

Above serial no. 917. Brimistors were often removed by later service engineers (sometimes being replaced by a simple 10K resistor or even a small length of wire), but in this amp it remains. One can always spot AC100 mark 2s, however, even when the brimistor has gone - either by the remaining standoffs (which are regularly left in place), or by the two holes provided for them in the chassis.

Note that the red warning plaque on the back panel comes in with the brimistor. Older amps have white plaques. Serial plates continue, however, to have two plain metal compartments.

Serial number 732

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Chassis number 1407. One of the stands for the brimistor (now gone) is visible in picture 6. Overall condition of the amp good; only a few changed components here and there. The output transformer looks like the sort of unit that Triumph habitually used, but it may be a replacement. Note that the warning plaque on the back board is still white.

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Above, pictures of the amp as sold on ebay July 2013. A new choke supplied.

Serial number 734

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Existence reported on this Facebook page.

Serial number 736 - USA

Existence reported c. 2008 by "frankenprops" on an old Plexi Palace forum thread (long gone unfortunately).

HEREON - THE WARNING PLAQUE IS NORMALLY RED

Note that the appearance of the red warning plaque corresponds pretty closely to the appearance of the Mark 2 circuit (the circuit with a brimistor). Serial number 732, above, is obviously an exception, so too serial numbers 797, 800 and 813, in the opposite direction, below. But the correspondence otherwise is good.

Serial number in the 700s (?)

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Chassis no. 1476. Back panel recovered and grille cloth replaced. The covering on the back panel is tacked on so can be removed. The replacement grille cloth is nicely done so will remain. Condition of the amp is very good. The bias circuit has been adjusted and is somewhat more sophisticated than the original circuit; but otherwise few changes (though the choke is probably new). The on-off switch needs replacing, but that will probably be more or less it. The amp was formerly owned by Pat O'Brien of "The Priests of Love" - some great performances on YouTube.

Note the holes for the brimistor stand-offs. The brimistor and its stands were removed at some point.

Capacitor codes "WD" = April 1965. Pot codes "EM" and "HM" = May and August 1965.

The mains lead, now hardwired, is likely to have been the original - old British colours (red, black and green). The mains suppressor cap. by the switch is English (Radiospares), as it is in serial no. 756, below. These caps were added in England (to meet Underwriters Lab certification) to amps that were earmarked for export to the USA.

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Serial number in the 700s / 800s (?) - currently in the USA

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Chassis no. 1483. Serial plate gone. Mains and output transformers replaced. General condition excellent, and original 2W Erie plate resistors still in place. Stand-offs for the brimistor (now gone) visible behind the choke. Existence of the amp noted on a Plexi Palace thread - . Thanks to Mark for the pictures.

Serial number 748 - currently in the USA

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Further views of the amp: excellent general conditions, original transformers, though a replaced choke. The holes for the brimistor (now gone) stand-offs are clearly visible in the last picture.

Serial number 749 - currently in the USA

Chassis no. 1439. Thanks to "voxjunior" for the details.

Serial number 756 - formerly in the USA, currently in Russia

Below, older pics

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Sold on ebay in early June 2010. Looks to be in good condition. Visible through the mesh in the last two pictures are the transfomer part numbers (66775 and 66776). The mains input socket is an Amphenol four-pin XLR, but the twin output sockets are now 1/4" jacks. Note the presence of the large grey Radiospares snubber capacitor in the preamp behind the indicator lamp, indicating that this amp was made for export to the USA.

Serial number 760 - currently in the USA

External condition is good. Some extra circuitry added internally.

Serial number 772 - currently in Connecticut

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In great condition - the preamp is almost completely untouched - and still the original XLR and mains sockets on the back panel. There are relatively few AC100s in such good condition.

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The cab belonging to the amp. Superb condition. One of the Celestions has the code 18HK = 18th August 1965, and one of the Midaxes the serial number 15910. Note the rectangular Cannon connector. Thanks to Tom for the pics.

Serial number 783 - currently in the USA

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Chassis no. 1528. In excellent condition, and only a few changes here and there. The pictures above show the amp prior to a service. More will be posted when the amp returns from its check up. The date code on the Woden choke is FW = June 1965.

25 March 2012: below, post restoration. Thanks to Tom for the pictures.

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Serial number in the 700s - currently in Seattle

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Above pictures of the amp alone, thanks to George. Chassis no. 1410. The choke has the date code "EW" = May 1965. Below, now paired with a contemporary speaker cabinet. The serial number plate, which bears the number 785, is reproduction, along with the warning plaque.

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The speaker cab, which has its original speakers, horns, and wiring, has been renovated with new grille cloth. Note the rectangular Cannon XLR connector. Round Amphenols had come in, where cabs are concerned, by serial no. 800. See the entry below. Thanks to Walt for the new pictures.

Serial number 796 - currently in Italy

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The stands for the brimistor (since removed) are just visible in the first picture. The mains transformer probably replaced some decades ago. A few new capacitors here and there. The original gold-colour zener diodes survive on the underchassis tagboard.

Serial number 797 - currently in the UK

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In reasonable condition externally. White warning plaque on the back panel and the original Amphenol speaker socket. The mains socket is now a Bulgin. Some additions on the control panel - a further potentiometer and what may be a standby switch.

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Additional pictures: Chassis number 1575. The choke has the date code "HW" = August 1965. One of the green TCC capacitors in the preamp has "WE" = May 1965. The Welwyn cement 470R resistor on the speaker terminal block has "WD" = April 1965. Three of the original Erie 1-2W plate resistors survive.

Serial number 800 - currently in Italy

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Amp, cab and trolley, and original speaker cable with Amphenol XLR connectors. Note that the warning plaque is white.

Serial number 813 - currently in Italy

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Chassis number 1469. The choke has the date code "HW" = August 1965. The 0.25uf Radiospares cap. (often removed) is still in place in the bias string.

Serial number in the 800s? - currently in the USA

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Sold on ebay in 2007. Chassis number 1500, so serial number probably in the 800s. The photograph of the plate itself, sadly, is blurred, as are a few others. Probably a re-wound output transformer. The Woden choke has the code FW = June 1965.

Serial number in the 800s? - currently in the UK

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An AC100 belonging to a UK Beatles tribute band. A link will be provided to their site when that comes to light.

Serial number 825 - currently in Italy

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A nice-looking AC100, perhaps with its original cab. There are no shots of the electronics, but one can see on the back panel, the Amphenol XLR output socket. The mains socket has been replaced. For the site of origin .

Serial number 830 - currently in the USA

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Amp and cab in great condition - red warning plaque, original Amphenol connectors still in place on the amp. The cab has (as is the norm at this point) a rectangular Cannon. The trolley is missing its lower half. Inside the amp cabinet, one can see a chalked "5". On the inside of the backboard, a feint "2". The original mains cable to the connector on the backboard survives intact, so too the cable from the terminal block to the Amphenol speaker connector.

Serial number 831 - currently in the USA

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With its original speaker cab. Thanks to Mike for the pictures.

Serial number 834 - currently in the USA

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A handsome rig in full working order. Chassis no. 1677. The present trolley was acquired separately from amp and cab which have always been together. The backboard of the amp is simply for convenience - the original still survives. The Fanes were installed when the rig was acquired in the 1970s. Thanks to Steve for the pictures.

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Pictures pre-restoration

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Pictures post-restoration (2015)

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Expertly restored by BLC.

Box with serial number 836 - currently in the USA

To note for the time being that serial number 836 has recently come to light in the USA. The chassis appears to have a heat shield around the EL34s, though, first seen normally on the chassis of amps with numbers in the 1100s. There are no pictures of the electronics at present. Thanks to Chris for signalling the amp's existence.

Box with serial number 844 - currently in the USA?

Made by Triumph

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Sold on ebay in March 2012. A near immaculate AC100 rig. The amp was assembled by Triumph Electronics. Boxes, complete with backboards and serial numbers, were provided in a slightly random fashion at JMI. For further pictures, see the triumph-made amps page.

Serial number 854 - currently in the USA (collection: Andy Sandler)

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Serial number 859 - currently in the USA

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Chassis no. 1471. Great overall condition. Thanks to Robert for the pics.

Serial number 862 - currently in the USA?

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Serial number 862 along with its original cab and trolley. Pictures from ebay a little while ago. Grey panel, two-line serial number plate, red warning plaque, original Amphenol sockets. A jack socket, probably for preamp line out, has been added on the control panel.

Serial number 867 - currently in the USA

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Serial number just too indistinct to make out from the pictures. Woden choke has the code "FW", as many other amps on this page. Output transformer replaced. The trolley is an American Super Beatle trolley - note the hooded castors. The speaker cabinet is English, a late AC100 cab made by GlaRev - "G-R" is stencilled on the shelf, and the baffle is Baltic ply, rather than the chipboard (particle board) of American-made cabs. The trolley fixings have been screwed on, rather than bolted. The speakers look to be from two sources - two perhaps original to this cab. though as the original wiring has gone, it is hard to tell; the other two certainly from a Super Beatle.

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Serial number 868 - currently in the USA

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Chassis number 1656. Output transformer renewed; good tidy work in the preamp and power section; the box restored with Thomas Organ grille cloth and a new back panel. The SDL speaker cabinet, speakers, and trolley were sourced separately. Thanks to Jack for the pictures.

Serial number 878 - currently in the USA

Vox AC100 serial number 878

Thanks to Jake for the picture.

Serial number 880 - currently in the USA

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Recently on ebay. Good condition. The speakers are now modern alnico blues instead of the original silvers, and the wiring in the cab has been replaced, but otherwise all there so far as one can tell. Original speaker and mains leads with latching Amphenol XLRs present. It may be the light, but the logo of the cab looks to have a distinctive edging to it.

Serial number 890 - current whereabouts unknown

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A single image of an amp that sold on ebay in 2006 for an extraordinary amount. A bidding war broke out and it went for something in the region of $10,000.

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