Keeping things going

Working on DS cabinets (may 2020)

It is very difficult to keep everything going. The oldest WANG machine is from 1972, the latest from 1990. There are spares and manuals, but even then you might not be able get a stable running computer but you are faced with all sorts of intermittent problems. And to be honest, who is waiting for the result ? How much time should I spend on repairing the old systems ? Beside that, I am an Agricultural Engineer, not really trained in computer repair. But, I do my best !!

Repairing the screen of the PCS II

The PCS II had been stored in unfavorable conditions for years I presume. On the front of the CRT a thicker piece of  a darker coloured glass is glued. You would almost think that some kind of fungi used the glue as their grazing ground. In a painstaking effort I have removed all the glue between the two surfaces. Aceton will help and you can make a flexible tool from a hack saw. The end result was a shining PCS II !   

Never waste a crises !

Normally, I spend a lot of time on my steam hobby. But with the covid-19 crises, I suddenly had time to work on my old computers. Certainly in April and May 2020 I spend a lot of time in the museum. But as a result, I got a lot of equipment going again. The most annoying problem are the Micropolis hard drives. They stop working after 25 years. No one to blame, these drives had an estimated lifetime of 5 years. All in all I got 5 drives in working order. Lets hope that there is more lifetime is these wonderful pieces of enginering!

I am sure that if you had the right tools and instructions, a lot more could be done, but that information is long gone. Micropolis went down in 1996.The 6 drives in the left bottom corner on the image above are all in error.     

Key board repair

Typical WANG keyboard with top cover removed
The half-moon pattern and the new pads

From 1980 to 1990 WANG used keyboards made by the Keytronic Corporation from Spokane WA. These are  keyboards with capacitive-based switches, one of the first keyboard technologies to not use self-contained switches.There is a sponge pad with an aluminium foil on top of the switch plunger. If a key is depressed it touches two half-moon trace patterns on the printed circuit board below. This gives a change of capacity that is detected by the electonics and the correct code is send to the CPU.

The problem is that after many years, the foam deteriorates and instead of 3/8″ high it is now only 1/8″. The key no longer gives a response. Luckely there is a small company called TEXELEC that can supply new foam and foil capacitive pads. If you want to do it properly, you have to remove all the keys and that is a time consuming job indeed.

The key can be taken apart, de old foam pad removed from the plunger and replaced by a new one. The foam is glued to a plastic disk and is attached to the plunger with four small clips. (very vulnerable, take care !). After reassembling you have a perfect working keyboard again for just a few dollars !

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