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Leo II Valve Rack

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One of the many valve racks that would have been installed in a LEO II computer.

This is probably a Register or a store unit. It has a change label on the side dated 11/6/1959, and a number 857701A/P2.

It also has a test date of 19/5/1960 and A5 written on the label side, on the other side is another mark of ECC 91 and a tick.

Valve checking policy changed many times - the transmitter/receiver would have needed regular setting up to maximum performance in the test rack. These ECC91 valves may have needed special attention.

The rack is part of our onsite display for the National Lottery Heritage funded-project 'Swiss Rolls, Tea and the Electronic Office'.

LEO II computers were installed in many British offices, including Ford Motor Company, British Oxygen Company and the 'clerical factory' of the Ministry of Pensions at Newcastle. LEO III computers were installed in Customs & Excise, Inland Revenue, The Post Office and in Australia, South Africa and Czechoslovakia. A full list of LEO II and LEO III installations is available from the LEO Computers Society website.

This Unit Was Kindly Donated By Phil Hamilton.

Phil used the rack as a lecture tool, while travelling around universities, along with a wide range of slightly more modern boards, teaching the early history of computers.

He gave us the story of how the parts came into his possession 

I knew two English Electric Leo field engineers very well, they were always after 'easy fixits' etc. One of them had a box with old computer parts in the back of his van. 

I asked where he was going with them and he said "to the nearest scrap pile" I asked for the bits and he said gladly, they're yours for the favours you've done us.

I told him that I would keep them personally and I remember him thanking me for saving him the run to the scrap pile, wherever that was.

That was early 1970's. It wasn't until the early 90's that I started lecturing and they at last had a use after nearly 20 years storage. I was using them until end of semester 2, 2008, so they were my props for 18 years’

Phil Hamilton

19th March, 2020.

Manufacturer: LEO Computers LTD
Date: June 1959

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Leo II Valve Rack Articles:

Item Manufacturer Date
Mike Cowlard: Reminiscences of a LEO Operator Unknown
Barry Hooper, Programmer Shell Australia Unknown
Hackney Archives Unknown
Higher Systems Unknown
Steve Farrow: Interview Leo Computers Society Unknown
Graham Briscoe: Reminiscence Unknown
Dick Cromwell: LEO Memories Unknown
Ray Dawson: Reminiscences Unknown
Mike Finlay: Memories of LEO Unknown
John Simon Florentin, Computer Operator Unknown
David Holdsworth: Reminiscence Unknown
Stan Holwill: My LEO Involvement & Memories Unknown
Maurice Bonney: Memoir LEO Unknown
Ron Marshall: Reminiscence Unknown
Peter Mills: Reminiscence Unknown
Ray Smith: Reminiscences of a LEO III Operator and Intercode Programmer Unknown
Anthony Robin Davies: Commentary LEO Unknown
Mike Tyzack's story with Leo computers Unknown
Faith Van Rooyen Unknown
John Goodwin: Reminiscence LEO Unknown
Harry Warner: Reminiscence Unknown
Emil Gottwald: Reminisence LEO Unknown
Pat Whitaker: Commentary Unknown
Norman Witkin: Memoir of working with LEO in South Africa Unknown
Denis Hitchens: Reminiscence LEO Unknown
Colin Hobson: Reminiscence LEO Unknown
New Computers for the Post Office Unknown
Joe McNulty: Memoir LEO Unknown
W.E.J. (John) Parry: Memoir LEO Unknown
Chris Reynolds: Memoir LEO Unknown
Mike Smith: Memoir LEO Unknown
Michael Wilson: Commentary LEO Unknown
Andrew Wylie Unknown
Nigel Furness: Reminiscence Unknown
I Love ICL Unknown
Museums Victoria, Melbourne Unknown
Peter Baker: Reminiscence Unknown
John Fletcher: Reminiscence Unknown
Brian Grimshaw: Reminiscence Unknown
Ron Kirby: Reminiscence Unknown
John Oates: Commentary Unknown
Penny Woodward: Reminiscence Unknown
Chris Parker: Comment Unknown
Alison Taylor: Reminiscence Unknown
Stan Evans: Reminiscences Unknown
On-line Leo III User Manuals Unknown
Peter Mills: Memoir Unknown
Brian Skillen: Memories of my time operating LEO I Unknown
Explore our LEO Computers Collection Unknown
Electronic Computers & Their Possible Applications LEO May 1955
Electronic Computers in the Office 1956
Electronics in the Office 1957
Maintenance Procedures on a Computer Jan 1960
Advanced Data Processing 22 Jul 1960
Introducing LEO III 12 Aug 1960
Computers for Shell-Mex and BP 1962
Current Developments in Commercial Automatic Programming 1 Aug 1962
Wythenshawe: The Second Computer Centre for Shell-Mex and BP 1963
The Management of a Large Commercial Computer Bureau LEO 1964
An Introduction to Compiler Writing Jan 1965
Hardware in Europe May 1965
The Brains Behind The Buttons 5 Jan 1967
LEO III/7 Fire Sep 1967
LEO III: a rave from grave 4 Sep 1975
John Pinkerton: Self Interview 23 Aug 1988
Interview with Les Turtle 1990
Betty Newman (Betty Cooper): Interview Sep 2001
London’s Home Movies 2003
Timesharing History: the UK Story 2004
Report on visit of inspection to LEO III/ in Edinburgh Museum 2007
LEO Computer Reunion 2010 18 Apr 2010
TR Thompson – The Leo Computer: A London connection Oct 2011
Tony Morgan: Interview Leo Computers Society 8 Nov 2011
John Daines: Interview Leo Computers Society 26 Apr 2012
LEO Computers in Australia LEO 2013
Software, A Progress Report on the LEO III Intercode and Master Routine Emulator LEO 2013
Alan Sercombe: Interview Leo Computers Society 23 Jul 2014
Corby & The Electronic Brain: LEO II 2015
Discover Corby’s computing heritage with new exhibition Sep 2015
British transistor manufacturers in the 1950s 2016
Paul Dixon: Interview Leo Computers Society 4 Apr 2016
Derek Jolly: Interview Leo Computers Society 11 Apr 2016
Patrick Blakes: Interview Leo Computers Society 27 Jul 2016
Peter Bird: Interview 6 Sep 2016
Ian White: Interview 6 Dec 2016
Key Points in 2001 2017
Alistair Cochrane: LEO Operating Memories 2017
Michael Mills: Interview 7 Feb 2017
Tony Earnshaw: Interview Leo Computers Society 16 Feb 2017
John Page: Interview 11 Apr 2017
Ian Bruce: Interview 5 Jul 2017
Barry Fox: Interview 19 Jul 2017
Geoff Pye: Interview 3 Aug 2017
A Virtual LEO III 2018
Brian Mills: Interview 27 Feb 2018
John’s (John Parry) Story 2 May 2018
Alan Hooker: Interview 21 Nov 2018
Brian Hobson: Reminiscences LEO 18 Dec 2018
A Life in Computing 2019
Software - LEO III 2020
Michael Hancock 2020
Michael Guy: LEO Master Routine 2020
John Daines: Reminiscence 2020
Alan Hooker: Memoir 2020
Robin Davies: Reminiscence 2020
John V Panter: Reminiscence 2020
Tom Brooks: Memoir LEO 2020
John Gardner: Interview Mar 2020
Greg Wojtan: My Days with LEO 2021
Peter Guest: Reminiscence written by Margaret Guest 2021
Wendy Forward: Memoir by her daughter Anna C Page 2021
Bill Jack, English Electric Engineer (team leader) Ravenscraig LEO III, Recollection 2021
Helen Clark (Helen Jackson): Reminiscence Apr 2021

Magazines RELATED to Leo II Valve Rack in our Library

Item Manufacturer Date
The Computer Journal July 1960 Jul 1960
The Computer Journal April 1962 Apr 1962
The Computer Journal April 1963 Apr 1963

Other Systems Related To Leo II Valve Rack:

Item Manufacturer Date
Leo III Logic Board LEO Computers LTD early 1960s
55625 Program Wiring Subset Unit from LEO III LEO Computers Ltd c1965

This exhibit has a reference ID of CH56848. Please quote this reference ID in any communication with the Centre for Computing History.


Leo II Valve Rack

Click on the Image(s) For Detail


Introducing LEO III
LEO III/7 Fire
A Virtual LEO III
Corby & The Electronic Brain: LEO II
Software, A Progress Report on the LEO III Intercode and Master Routine Emulator
A LEO III: 21st Century Hindsight
LEO III Software Rescue
History of the Leo III Software Preservation Project: Blow by Blow Account
LEO II and the Model T Ford
Validity & Correctness before the OS: the case of LEO I and LEO II
Features of the LEO IIC Computer
LEO III: a rave from grave
On-line Leo III User Manuals
Report on visit of inspection to LEO III/ in Edinburgh Museum
"Check Everything”: Validity and Correctness in LEO III
Ray Smith: Reminiscences of a LEO III Operator and Intercode Programmer
Software - LEO III
Bill Jack, English Electric Engineer (team leader) Ravenscraig LEO III, Recollection

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