Donner Analog Computer Model 3500
YEAR: late
ITEM: Analog Computer
COMPANY: Donner Scientific Company
COUNTRY: U.S.A.
IN OUR COLLECTION: Yes
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 equation...you 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 BoardViewer Stories & Comments
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. .
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 :)
Documents
Documents for this item have not yet been scanned or not yet posted. There are a lot of pages...contact us if you have an immediate need. (Although there are not a lot of "immediate needs" for a 70+ year old computer!)
Exceedingly Rare
We know of six Donner Scientific Model 3500's.1. One is located at the University of Stuttgart in Germany in a museum run by the computer science faculty.
2. Bob Rosenbloom's collection way out in California contains several analog computers and he has two Donner 3500 computer.
3. Bill Degnan a collector who specializes in Commodore computers but has a talent with all sorts of computers is restoring a Donner right here in Pennsylvania.
4. I was recently (Dec 2013) contacted by the owner of a 3500 who is looking to sell it. We did not find out where it ended up.
5 & 6. There are two in our collection. One is an early Donner computer. The other is a later Systron-Donner that was located near Atlanta, Georgia, USA and was owned by a gentleman who designs robots near Atlanta, Georgia.
--We have an unconfirmed report of another Model 3500 at SMECC (Southwest Museum of Engineering, Communications and Computation) in Glendale, Arizona.
OUR DEFINITIONS OF RARITY
One of a Kind: Only known existing item.
Exceedingly Rare: Only 2 to 10 known to exist.
Very Rare: Only 11 to 25 are known to exist.
Rare: Only 26 to 50 are known to exist.
Difficult: Difficult to find.
Available:Can be commonly be purchased.
Unknown: We cannot make a determination.
(For comparison: Many people consider the Apple-1 computer to be rare. As of 2025 there are 92 confirmed and probable Apple-1 computers.)
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