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 YEAR: late 1950's
 ITEM: Analog Computer
 COMPANY: Donner Scientific Company
RARITY: Exceedingly Rare   Click here for further information on our rarity scale Information on the rarity of this item is unknown.

Donner Analog Computer Model 3500

A view of the vintage Donner Analog Computer Model 3500 an important part of computer history

The Model 3500 is a unique portable, analog computer. Weighing just 28 pounds and sporting two leather handle straps (one at each side) the 3500 was designed for use by scientists and engineering designers who could easily move the computer from one place to another. It could be used as a versatile signal generator, data reduction or signal conditioning at test sites, and as a general purpose computer in the classroom, field, or desk. Use for the classroom was convenient with 2 detachable problem boards controlling half the computer. There is a remote control for field testing. It was probably first offered for sale in the late 1950's. It was designed so that it could be a free-standing computer or it could be reconfigured to be rack mounted. The one in our collection is slightly different from those pictured in the "Instruction Manual Model 3500" in that it has a protruding, angled front control panel. We don't know if this is a standard factory version of the 3500 or a later customization.

How did you operate it?

Operating this computer wasn't easy. The Instruction Manual states that the 3500 should "warm up for at least ten minutes" before use. In addition, the manual recommends "a daily or weekly check should be made of the +300V and -150V power supply output voltages." [So don't complain next time your computer takes 30 seconds to power up!]

Porgramming was done by patchcords. This means that is you wanted to program the analog computer to solve an equation you had to configure the patchcords in just the right way. And if you then wanted to solve another had to unplug all the patchcords and reconfigure them. Imagine having to use patchcords instead of your keyboard or mouse or touchpad to enter information into your computer.

History of the Donner Scientific Company

Donner Scientific Company was founded in 1953 in Berkeley, CA by William Rosenberry and was named after Donner Pass. The company moved to Concord, CA in 1954. They began making the Model 30 Analog Computer (a vacuum tube computer) and sold 600 units between 1954 and 1960. Donner Scientific merged with Systron Corp. to become Systron Donner Corp. on March 31, 1960.

Systron Donner is still in existence in the same city. They are called "Systron Donner Interial" and make sensing devices (such as gyroscopes) for all sorts of modern tecnologies such as the Mars Rover (really, they are on Mars!), military helicoptions, UAVs, torpedoes and robots.

Related Items
      Related Item 1: Donner Problem Board

Viewer Stories & Comments
   Brad Sage     Lafayette CA, USA     April 27, 2018

       The Donner 3500 was an early item in their extensive analog computer line. Later, Donner invented solid state chopper stabilized operational amplifiers with an output of plus/minus 100 volts. These went into large rack size analog computers with one hundred or more amplifiers. The programming boards were removable modular units so a program could be set up at your desk and the unit plugged into the computer mainframe. Donner was not named after Donner Pass but after the Donner Labratory at U. C. Berkeley. N.B. I was employed by Donner (later Systron-Donner) for 45 years. .

   Andrew Davie     Hobart, Australia     March 26, 2015

       I have a Datanumerics DL-8A front panel blinking-lights computer from about 1976. It's the only one I know of still in existence. Just thought I'd make it known that there is one, and it still works :)

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Click on any of the images below to see the slideshow.
Front view of the Donner 3500 analog computer.  This rare analog computer was designed for engineers and teachers. Front and top view of the Donner 3500 analog computer.  The wires (called patchcords) were used to program the computer; imagine substituting that wiring process for the modern keyboard. View of the left side of the Donner 3500 analog computer -- notice the leather strap handles & angled front panel.  Right side view of the Donner 3500 analog computer -- patchcords have been removed. Back of the Donner 3500 analog computer.  You can see the manufacturer's tag and some extra large holes to let the heat dissipate. Closeup of the manufacturer's tag that includes the serial number.  You can also clearly see the company's name.  Later versions of this classic analog computer display the name Systron-Donner after the companies merged in 1960. View of the back of the Donner 3500 analog computer which opened easily for access to cards and tubes.  The tubes of an analog computer generated quite a bit of heat.  Closeup of the opened back of the Donner 3500 analog computer.  Note voltage range of +/- 100 printed on the frame just above the tubes. Closeup of the Donner 3500 analog computer patchboard from the top. Closeup of the Donner 3500 analog computer's patchboard from the front.  This is the same section of the patchboard shown in the previous picture. A view of the underside of the the Donner 3500 analog computer's patchboard.  You can also see the fan (covered by a screen) and the oblong openings that were used to dissipate the heat from the tubes. Closeup of right side of the Donner 3500 analog computer control panel.  This rare portable analog computer was an important part of computer history.