The Computer Church: The .

AMF Educational Computer Model 775A

We had been unsuccessful in finding information on this machine until David Liebers wrote us and referred us to a series of articles. (Thanks, David!)

This is a gigantic computer...one of the largest in our collection. The American Machine & Foundry Company (commonly known as AMF) made a personalized student version of this computer (Model 665/D) which allowed individual students to develop their computer skills; this personal sized computer measures roughly 12" by 12". However, if a teacher wanted to demonstrate computing methods he/she was out of luck...until AMF built the Model 775 computer which measures 37.5" wide by 28" tall. I can picture it sitting on a desk in the front of a classroom where every student can see clearly it.

Originally the only way we had to date the computer was a small sticker on the inside that says, "Accepted 1/24/72". We don't know if this was accepted right after purchasing it or if it was years later.

The voltage meter has the AMF logo followed by "Alexandria". There is a record of an American Machine & Foundry Company located at 1101 N. Royal Street which was torn down around 1999 and the Wall Street Journal quotes the Dept. of Energy, "This site handled (or was contaminated by) thorium and uranium, according to government records. The Department of Energy initially considered cleaning up this site under the Formerly Utilized Sites Remedial Action Program, but determined that it didn't have the authority to do so."

We received a note from David Liebers in April of 2020 that pointed us to several very informative articles about this computer. David was actually in a special high school class for budding engineers that used this Demonstration Computer.

The High school was Wausau East High school in Wausau WI. The year I took the course was the first full year the course was offered, 1969/70 school year. Part of the year we worked with the 665/D analog computer on such experiments as the falling ball experiments and projectile experiments. The rest of the year we worked with the 800 to build digital logic circuits such as binary adders. Since this was a new course, we only did some of the experiments in lab manual plus the official text book had not been published at this time

The course was called "Man Made World" and was part of an effort by the EECP. One of the articles describes the addition of the Model 775 Demonstration Computer to the "Man Made World" curriculum. The article helps us date the computer. The article is dated September 1970 so we know the computer is at least that old and likely older. I suspect it is a 1969 computer and we will continue to investigate its origin. Below is a section from the newsletter.

"LABORATORY DEMONSTRATION ANALOG COMPUTER

As noted in the last issue of the Newsletter, a major addition to the ECCP laboratory package is the Model 775 Demonstration Analog Computer. As some schools start the ECCP program with only one analog computer because of budget limitations, the provision of a unit designed for demonstration use in the classroom was considered essential. Even in schools having a number of the student model computers, the visibility of the Demonstration unit panel greatly simplifies class instruction. The Demonstration computer is shown in the picture below. The panel layout is an enlarged version of the student computer panel with only a few small differences. The background is white and the circuit connections are black to give optimum visibility. Two knobs are provided for the variable outputs of the power supply. The plus and minus voltage outputs can be independently varied thereby providing an additional independent voltage output. Finally, the Remote Operation connection has been eliminated since it seems unlikely that the Demonstration unit will be used with another computer.

The timer used on the Demonstration unit is the same as is used on the Model C student unit, having three time intervals as well as the manual or continuous integrator position. A projection meter is provided at no extra cost as a part of the Demonstration computer. As can be seen in the picture, this meter, used with an overhead projector, provides an easily visible output that is identical with the meter scales used in the student model computer. The meter connects to the Demonstration unit by a special cable and receptable [sic] so that there is no need to run a separate COMMON lead to the meter. However, the meter can be easily disconnected from cable if other output devices such as an oscilloscope or chart recorder are to be used. Storage space is provided in a compartment in the base of the unit, accessible from the back. All leads and the meter can be carried in this space. A handle is also provided to simplify transport of the unit.

These Demonstration units were available for use at all the ECCP summer institutes and now a number are in use in the schools. They are available at $430.00 each, from the AMF Alexandria Division, 1025 N. Royal Street, Alexandria, Virginia 22314.
by D. C. Miller" ¹

We had been quite perplexed by a clear plastic meter that was attached to the end of a long cord out the back of the Model 775 Demonstration Computer. The article that d1_liebers pointed us to showed us how that meter was used. It was actually placed on an overhead projector (which, like chalk, has disappeared... students, ask your parents or maybe grandparents) next to the Demonstration Computer so that the reading could be seen by the whole class.

¹D. C. Miller. (1970). ECCP Newsletter Vol IV, No. 2 (ED046718). ERIC. https://files.eric.ed.gov/fulltext/ED046718.pdf