Gallery
Soemtron Calculators Gallery
These pictures are (C) 2007 Serge Devidts, used with permission, for more see his site here.  Click an image for a larger version. | |||
 Soemtron ETR 220 |
 Inside view |
 Decimal point selection |
 Nixie tube display close up |
| All images (C) soemtron.org 2007,2008 | ||||
| Our unit arrives ! ........ | ||||
| When the unit when it arrived from Prague it was evident it had not been cared for over many years. It was extremely dirty, rusty and corroded and the power supply was missing with just the cut off wires from the temperature sensing thermistor and the power supply plug remaining. The keyboard and all of the keys were seized solid, none of them worked and it also turned out that most of the keyboard return springs had completely rusted away. Rust was also evident in many parts of the machine showing it had been stored in very damp conditions for a very long time. This machine is going to take a lot of attention to get it back to come sort of operating condition.Click an image for a larger version. | ||||
 Top view |
 Front view |
 Internals |
 Keyboard |
 General inside view |
| The rebuilding ........ | |||
Photos here show the parts of our Soemtron ETR 220 as we recondition and rebuild her, the improvement of some of these parts is quite remarkable. The keyboard was probably the worst of the assemblies from the whole sorry unit, all the keys were jammed in various positions and after careful dis-assembly it was found that this was caused by most of the key pins being rusty, with 80% of the key springs having rusted completely away, these were replaced with closely matching springs from our "bits" box. It also came to light that the last wafer of the DP selection switch was badly corroded and was working only intermittently. Careful dis-assembly and solvent cleaning has brought it back to life. In general all parts of this Soemtron ETR 220 were cleaned using only hot soapy water and then dried in a hot cupboard for about a week, badly rusted metal parts are carefully de-rusted with wire wool or emery cloth and then polished, again in hot soapy water with a cream cleaner, this brings up the remainder of the original plated finish and cleans off the remaining rust. We are not going the extent of re-plating the metal parts, but leaving them so what remains of the corrosion sites can be seen as an indicator of its original sorry condition. | |||
 DP Selection unit |
 Display and keyboard |
 Card cage |
 Rebuilt keyboard |
| Refurbishment completed ........ | |||
Our original Soemtron 220 that kicked this website off is now back together and fully assembled, photos are below and we think she looks quite good even if we say so ourselves!. All the dirt, dust, rust and crud has gone and without a respray she is as near to original as we can get her. The power supply wiring has been replaced ready for a new power supply when we can get down to building one or can find a donor machine. Compare these photos with those above to get an idea of the state this machine was in ! | |||
 Top view |
 Front view |
 Internals |
These photos (left) try to give an "after" to the "before" in the "Our unit arrives ! ........" section above. |
 Front view |
 Power supply side |
 Front view |
 Memory card side |
| The Extender Card ........ | |||
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 Extender board |
 Extender board socket |
 Extended board |
 Board and extender |
| The Boards ........ | |||
| This section has photos of each of the twelve boards from our Soemtron 220, each was added as we generated their respective circuit diagrams> Some of the boards require slight remedial rework, mostly to replace board links that are possibly shorting to nearby components and to shorten the leads of some capacitors whose leads are too long, which again could be at risk of shorting with other components. The boards are numbered in the same order as they appear on the inside of the card cage, that is board 12 (Cathode drivers and gating) which is nearest to the power supply, to board 1 (Core memory) furthest from the power supply. Apparently later revision machines were built in the opposite order, with the Core store nearest the power supply and board 12 furthest away, we presume this was to reduce the susceptibility of these units to temperature changes.Click an image for a larger version. | |||
 Board 12 Cathode drivers |
 Board 11 Anode drivers |
 Board 10 Position Counter |
 Board 9 Register addressing |
 Board 8 Function latches |
 Board 7 Function latches |
 Board 6 Control gating |
 Board 5 Function latches |
 Board 4 E Register |
 Board 3, A Register |
 Board 2 Core drivers |
 Board 1 Core store |
 Card rack numbering |
All of these boards are from the original unit, serial number 105669, and are shown after light cleaning with a small brush, otherwise they are untouched from the received condition. Some of the boards will need a little rework to cover some of the wire links that are rather close to components, straighten a few components and resolder a few joints. Then we will try to power her up for the first time in many years !. | ||
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