Re: Wang model 452-0

From: Rick Bensene - The Old Calculator Web Museum
Email: rickb@bensene.com


Hello, There could be myriad problems that could cause your Wang 452-0 to malfunction as it has. If the basement in which it was stored had any humidity problems, it's likely that corrosion formed on many of the connectors that interconnect the various sections of the machine. It is also possible that corrosion may have attacked some of the leads of components...some early 1970's IC's were made of a material that was subject to corrosion, and the pins of the IC's can actually break. If this happened to a lot of the IC's, this could make the machine very difficult to repair. One problem which can frequently occur on old electronics (especially digital electronics) that sit unused for long periods of time is that of power supply capacitor malformation. The capacitors lose their ability to filter out alternating current over a long period of time without power being applied. In the power supply, large filter capacitors help to smooth out the ripple from rectifying the AC voltage(s) put out by the transformer. This can cause AC 'noise' to leak into the logic circuitry, which will cause the machiene to malfunction. Also, smaller capacitors are used at the power leads of integrated circuits to act as small 'shock absorbers' to smooth out transients on the power supply rails caused by switching of logic devices. Firing up a machine after a long period of storage without doing so in a proper manner (typically involving 'reforming' the capacitors through use of a variac) can cause damage to sensitive integrated circuits, especially the early large-scale integrated circuit devices used in these machines. Assuming that your machine suffered no damage as a result of powering it up without taking precautions regarding the power supply capacitors, and that corrosion is not a factor, there could be some other relatively simple causes. A failed section of the power supply, e.g., a bad fuse, could be the cause. Given that the display sometimes lights up a few digits as the machine is powered off, could indicate that one or more logic supplies is missing. Another issue could be a stuck or shorted keyswitch on the keyboard. Many calculators will 'lock up' if a kew switch is shorted, making the machine think that a key is being pressed continuously. Lastly, it could be that some component of the machine has simple falied. The machine used early large-scale IC's made by (I believe) AMI, and these chips pushed the state of the art in terms of component density. IC processes in those days weren't quite as 'locked down' as they are today, and manufacturing methods were not as sophisticated. It's possible that one of the LSI's has failed, which would render the machine inoperative. Unfortunately, finding these parts today is next to impossible, unless you happen to find another calculator to use as a parts donor. In terms of value, I make it a policy not to provide valuation of old calculators. Obviously, though, in non-operational condition, the machine is not worth nearly as much as one in operational condition would bring. Factors which contribute to value are: aesthetic condition, presence of all original labels and tags, operational status, availability of original documentation (user's guide and associated materials), original power cord and dust cover, availability of any original sales documents (bill of sale/invoice, any advertising or marketing literature), and service records. I hope that you find this information of some use. Regards, Rick Bensene Curator, The Old Calculator Web Museum http://oldcalculatormuseum.com