- Blog entry posted in 'Teardowns', April 08, 2013.
Yes, this is already at ETO forums, but i was told that this could be great addition to blog, and this was indeed great find!
I noticed this typewriter at flea market for 2€, lable said also condition=? (untested) so i thought, what the hell, its only 2€, there's gotta be something of value in there, and I'm too curious to pass this cind of opportunity to pass. when i got home, no fellas, sorry to disappoint you but i couldn't resist to turn it on first before breaking her apart. Well it turned on ok, BUT surprise, ERROR light lit up after initiation checkup. Hmm, wonder what's problem. I opened it up, and found pencil head that obstructed writers horizontal movement. now it worked like charm, followed even my typos....well, what did i notice?:
Well, it was pretty easy to open, at first there was no screws to be seen, but there were couple at ''machine'' room. Then, the paper rolls (hope that's its name?) had to be taken off, which were held place by locking ''cross-fitted'' hex screws. after that, half of machine lifted off. At the main power board was some filter caps resistors and main fuse, with bit strange holder, accepts normal and long size fuses. The transformer was surprisingly big, probably because there is no SMPS, only linear, but I'm not sure does that effect transformer size. Transformer had marking: 2202405060, possibly 220-240VAC 50-60hz? output voltage is unknown as for now, but power rating is probably around 75w, as that is whole system power consumption
The horizontal movements and all ink ''placement'' and stuff was controlled by two pretty big one stepper motors, 4 wire (bipolar?), couple brushed motors, other even had changeable brushes, pretty rare these days for that size. And the ink placement itself was processed with solenoid, which just stamped letter. The feedback for this system was processed by opto-components, pretty handy, i would have guessed micro switches but this was pleasant surprise.
The main logic board was well, full of logic's and discrete components. Bunch of 74-series logic's, some ROMS too and other components . I don't know about ROMS/RAMS anything, but 74 is more familiar. brands were SGS, TI and such, good stuff :). all connectors were standard, not custom models. The filtering (?) after transformer was made with 3300 MFD 40v caps. i couldn't believe that they would be 3300 milli farads by that size, and so my cap meter showed also 3300 micro farads. apparently this model was that age, when there was no mikro-letter in use. ESR was also in good mood, 0.1 ohms. other components at filtering was pretty big looking diodes and fuses.
At keyboard there wasn't much of interested, bunch of 1n4148 signal diodes. At LED board there was couple of IC's more, 74 series and apparently resistors for LED's.
But, that's all for now :).
