Analog (analogue) computers and plotters

This Web page last updated date Dec 13 2010, minor edit Oct 27 2015.

This Web page is about analog computers and related items such as X-Y analog plotters.

Electronic Associates Inc (EAI) analog computers

I have a TR-180 analog (actually analog & digital) computer from EIA. Here's some photos of it. I got it in 2007? and not powered it up. It's in a blue-painted cabinet; some models I've seen were embedded in a wood cabinet with a drawer below.

EAI-180 front panel. What looks like modules, are just decals. The front panel is one piece or a few pieces, the "modules" are not removable like earlier models.

Detail photos: EAI-180 meter, indicators, controls
EAI-180 mode controls and binary switches
EAI-180 comparators and pots
EAI-180 logic gates and flip flops
EAI-180 integrators and summers
EAI-180 product tag and serial number

On the computer is a tag from Royal Military College of Canada - EE Department I checked their Web site in 2010 and was surprised to find they have more EAI-180's!. "Control Systems Lab - 7 Lab-Volt AC/DC servomechanism experimental units, 8 Feedback DC servomechanism units, 6 EA1-180 analogue computers, 10 Pentiums based analogue to digital acquisition systems for real-time measurement and closed-loop control." Note the misspelled "EA-one" rather than "EA-eye".

I have the following EAI PACE manuals as originals; I'm prepared to make photocopies of these, I list approximate prices. Actual copies would be priced at 20 cents a page plus postage and handling.

EAI PACE TR-10 Maintenance Manual at probably over $25
EAI TR-10 app note #1, probably a few dollars
EAI TR-10 Operator's Handbook, probably about $10
EAI EAI Handbook of Analog Computation, probably over $25

I have a EAI Variplotter 1100E, and manual. Photos of the plotter "soon".
EAI Variplotter 1100E manual, probably about $15 The plotter looks like this

Heathkit EUW-19A analog computer

Heathkit EUW-19A (see image) Operational Amplifier System. Malmstadt-Enke type, from the Malmstadt & Enke's book "Electronics for Scientists" which describes this EUW series of Heath products. The book shows the EUW-19 model; the "A" version is slightly different, see this image of the front panel. (An actual manual, or copy of one, would be of interest to me.)

Five vacuum tube operational amplifiers from the 1970's, for the analog lab! Very retro product for the late vacuum tube era - that's right, 12AX7 op amps! There are EIGHT 12AX7s in this unit, among others as seen in this photo. All tubes are "Mullard" brand. Amps spec'ed for gain flat to about 100KHz. Cosmetics fair to good. Interior photos show some surface rust but components look good in general. Obtained March 2006. Will not test, as given age chances are you'll need to check all the paper "condensers" and so forth. Value of this item in the few hundreds of dollars or more, it's an ANALOG COMPUTER which is of collectable interest.

For more information about some Heathkit or Heath - Zenith computers built and sold in the 1980's, check my Heath/Zenith Web page.. For information about test equipment and other plotters, check my test equipment Web page.

HP 7090A Measurement Plotting System

The HP 7090A is a 6-pin desktop plotter with three analog input channels which are digitized at 33KHz for 3KHz storage and plotting. There is also a date/time clock to date stamp the plots, a LCD character display to show status, signals and setups; and an IEEE-488 (HP-IB, GPIB) control interface. They don't make plotters like this anymore! Here's an image of the plotter. Details of these features:

Links around the Web, not comprehensive

Here's a visitor's photo of one EAI-180 (mine has an analog meter, not a digital display) at Bletchley Park, the UK site where German codes were decrypted in WW II. They also have a national computer museum. I can't find a link to their EIA computer at their Web site.

Thanks to the Analog Computer Museum Web site I see there's a TR-180 at the Powerhouse Museum in Australia.

I believe there's a TR-10 or TR-20 at the Vintage Computer Federation vintage computer group at InfoAge near Wall NJ, where they have a public museum. VCF has a Web site at this domain.

Mike Loewen has a TR-20. He's a colleague of mine.

A search for TR-20 yielded this manual at A collection of manuals on the site is at this WEb link.

Herb Johnson
New Jersey, USA
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