The Vox UL730 power section schematic – OS/114

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Above, OS/114 for the Vox UL430 and Vox UL730 power section, dated 28th February 1966.  Note that a small batch of pre-production amps – made at much the same time as the Beatles’ small-box 7120s – were built differently.  At least one of these early 730s survives (currently in the UK).

OS/114 indicates that the negative feedback line should only be for UL430 bass amps (FOR BASS MODEL ONLY).  As mentioned in the post below, UL760s had no feedback circuit to begin with, but at some point mid production one was subsequently added.

A Vox UL430 chassis on the work bench.  Note the small ding at the lower left corner.  This amp does not seem to be among the 430s already registered on this page.  The amp is included in the corrected total known to date a couple of posts below.

Possibly the same amp photographed more recently, though the detail is too small to tell for certain.

Pics of a further Vox UL710 added here, from an auction a little while ago, a distinctive scuff on its control panel.  Probably currently in the USA.

Most 710s have Bulgin mains sockets on their rear panels (including the one just posted). No. 1099, however, has an Amphenol.

Pictures of Vox UL 730 serial number 3002 with and without a cab now brought together.

Pictures of Vox UL430 serial number 1047 registered here, and three pics of serial no. 1052 in its former home in Messina added.  Six UL430s are now known (one not pictured) – five amp and cab sets, one amp + 460 trolley.

29th Oct. 2017 – to correct the statement above, it turns out that at least eight 430s are known to survive – five amp and cab sets, and three amps alone.

Pics of two 4120s added on this page  – serial number 235, which is new.  Thanks to Tim.  And an amp that spent a good deal of its working life in Wales paired with a Super Foundation Bass cab (towards the foot of the page, among the amps with missing serial plates, or numbers simply unknown).

Old pics of 213 have been now been matched up with a newer set showing the serial number.

Ten 4120s in total are currently known.  It seems likely that others will surface.

A series of updates are in the offing (this coming weekend):

For the time being, a couple of 760s which came to light recently in the UK – serial numbers 1004 and 1041. The amps have been registered here.