The Vox UL7120
Along with the 4120, the Vox UL7120 is probably one of the only production amps to have been built with a choke input filter power section. Solid state rectifiers first supply a massive choke, which then presents a smoothed voltage to a capacitor network (two 220uf / 350v electrolytics in series). The aim was to produce as solid and stable DC voltage as possible.
Screens and plates have around 582v on them. Bias is around -80v. Beware. Unloaded, that is to say with the KT88 power valves removed, 640v appears on screen and plates.
As in the case of the 4120, make sure the electrolytic capacitors in the power section are in good order. A bad or almost spent one can be boiled by the HT supply.
The preamp - schematic OS/117 - is the same as that of the 715, 730 and 760.
Probably around forty 7120s survive today. 760s are comparatively much rarer.
Amps are registered in two sections: (1) by serial number if known; and (2) lower down the page, serial numbers unknown.
Serial numbers begin at 1000 or 1001. Note that they are not a reliable guide to relative date, ie. amp no. 1030 could be later than amp. no. 1040.
John Lennon's amp sold at auction in 1985. Click for a larger version of a screen-grab from the Philadelphia Inquirer website. The live webpage is here .
John and George's amps in Studio 3 in mid April 1966. It is impossible to say which of the two amps John took away to Kenwood, then Tittenhurst Park, and New York. Paul's amp, with a BASS flag and closed-back cab, arrived a little later (certainly by 1 May '66). Image from this page.
Early box - removable back panel
Sold on ebay in 2009. The box is of the early type with removable back panel and single carrying handle. The amp, which was doubtless put in at factory, is later - in other words, an old box was used to house it.
Serial number 1001
Condition excellent. For some time in Germany, currently in the USA.
Serial number 1023
Currently in Australia and in great shape. The first two pics with a repro cab and trolley. Note the stamped number on the reverb pan - 145583 - and the paper ticket on the mains transformer - 7344. Visible pot codes are "GN" = July 1966.
Serial number 1041
For some years in Northern Germany, now in the United Kingdom. Excellent condition. Currently on offer - see this page.
Serial number 1045
Depicted on the left with repro cab and trolley. The amp on the right, with single central handle, is a different one.
Serial number 1056
Currently in the USA. Thanks to Mark for the pictures.
no. 1056 in the course of restoration. Pot codes are "GN" = July 1966.
Serial number 105
Plate (not a repro) removed from a 4120 amp.
Top, two 7120s owned by Jimmy Page, found for him by Carl Nielsen. Bottom, one of the amps on the Rockbottom Music Facebook page.
A 7120 currently in Spain, seen in the video above. The amp is probably the one below, sold on ebay in 2006. Note the jack socket of the normal channel.
Formerly in the USA, now in Spain. One of the jack sockets replaced, but otherwise in excellent cosmetic condition.
Formerly in the UK, now in South America (Paraguay). Pictured right with an original closed-back 4120 cab and repro trolley. The last picture is from an ad. for the sale of the amp on Gumtree, late 2015.
A 7120 and 760 cab found in Sicily some years ago, perhaps the remains of a Super Stack.
Currently in the USA.
Sold on ebay in Holland in 2012. Recognisable by the ding to the upper fascia.
Currently in the USA. Stencil on the left-hand side.
Currently in the USA. Trolley and cab are early repros, the trolley made by a welder in New York City in the late 1990s/early 2000s.
Currently in the USA. Pictured with a repro Super Stack trolley and cabs.