Re: Litton-Monroe 1800-series?

From: Rick Bensene - The Old Calculator Web Museum


The Monroe 1800-series machines are not terribly rare, but also aren't all that common...kind of a middle-of-the-ground machine in terms of rarity. They are definitely more common than the Compucorp-branded versions of the same machines (Compucorp designed the machines, and Monroe was an OEM customer). The Compucorp-branded machines seem to be quite uncommon. They are pretty high-powered machines, with good-sized memory capacity, a large instruction set, and peripheral interface capabilities. In my opinion, they are worth rescuing. The most common failure on all of these machines seems to center around the printer itself and printer driver circuitry. Common faults included failed hammer electromagnet drive transistors, and failed optoelectronic position sensors in the print mechanism. The common failure mode of the hammer driver transistors is for them to short, which can cause the "magic smoke" to leak out before the power supply fuses will blow. Other failures center around the mag card reader, with 'gummy drive wheel' syndrome being a common malady. Finding accessories for the machines (documentation, program libraries, mag cards) seems to be much more difficult than finding the machines themselves, so if you find one with such accessories, it's a bonus. Rick Bensene The Old Calculator Web Museum http://oldcalculatormuseum.com