Synthesis-2 - domestic clone ZX-Spectrum

While cleaning the village on a recent weekend, I found in the attic deposits a proud creation of Soviet electronics engineers - “Game Computer“ Synthesis 2 ”.



Without further thought, it was decided to immediately take him out of this wild place and see what he was capable of at work. Who is interested in the process of launching such antiquities and additional clickable photos - please under the cat.

Some theory

A series of computers "Sintez" (yes, there were several of them, but more on that later) - nothing more than another clone of computers ZX Spectrum based on a Z80A chip with a clock frequency of 3.5 MHz . Produced, depending on the version, with 128 or, as it was in our case, 48 KB of RAM and 16KB of ROM . Supported a color image in RGB format, displaying 8 colors with a resolution of 256x192. It was bundled, in addition to the operating instructions and a small reference book on the built-in Basic, with a power supply unit that converted 220V AC to 5V 1A DC, a set of cables for connecting to a tape recorder and a TV and depending on the configuration, joysticks.
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Inspect the computer from all sides

Rear panel. From left to right: Power supply jack, TV jack, “Reset” button, tape recorder and joystick jacks.



The label on the bottom panel:



"Under the hood":

Preparing for launch

But, nevertheless, let us return to the main goal - to start the computer.
We turn on the power supply in the outlet, connect the power supply to the computer. The LED on the front panel lights up. Power is there - gives hope that the PC is working. However, to make sure you probably need to connect it at least to the TV. The wires from the five-pin (for the tape recorder) and seven-pin (for the TV) plugs are practically nowhere to be inserted, so a page was found in Google, where the diagrams of the wiring of the video cable to SCART and the audio cable to two regular 3.5 Jacks were shown.

Immediately make a reservation - when I soldered everything according to the instructions from there, nothing worked: the image was white stripes along the screen, and there were unpleasant wheezing from the TV speakers. Without losing hope, we are looking for the original computer layout, looking at which shows that the pin assignments of the TV jacks and the tape recorder are different from those listed on the site. Well, apparently we have another modification.

Schematic diagram of the computer "Synthesis"


Without going into details, I will give a modified scheme of soldering to SCART and to Jack of cables for this particular modification:




I want to draw attention to the resistance of 200 ohms on the sync channel, a deviation of even 100 ohms from this rating led to a loss of image color.

Let's run it!

Making sure that everything works - try to download some kind of classic toy. Since there was no cassette, and especially cassettes with programs for the Spectrum, we took a netbook and a softphone to play * .tap files - winTZX as the source of sound with the game.



It looked very ironic - the computer of 1993 of release loads software from the computer, thousands of times more powerful than it. We introduce the familiar LOAD “” to everyone, click “Enter”, turn on the playback ... but by all means, who cares about the process - here’s a video with a download and a little summer play in the good old Space Raiders:

Conclusion

Surprisingly, the computer maintains a fully operational state to this day. The keyboard is pretty worn out, the keys are pressed almost without effort, but it works!
Running a few more toys, we finished our work with this PC. Now his place is in the museum.
Finally, another photo of the loading screen:



So here it is - the domestic Spectrum.
Thank you for attention.