Monthly Archives: March 2020

AM modulation, schematics, lots of transistors and perfect modulation

I was testing various AM radios and noticed that I don’t have a proper AM source. The AM broadcasting station in my region is very scarce and weak. Also, I wanted more options for radio receiver testing. I thought that … Continue reading

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Simple Sinewave generator

There is simple and good way to generate quite pure sine wave: This circuit is not very simple, but results are quite fine: output is pure sine wave. From the other side, this schematics have some minuses: it is hard … Continue reading

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After building ZX Spectrum clone in CPLD I ported hardware code to another project and this is a bit simpler, but it uses some mono LCD from old copy machine. Now I used only one CPLD, but I added an … Continue reading

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Cartridge for Commodore 64

Sometimes I want to show how old 8 bit computers work for some n00bs. It is nice to load some games from tape, some from disk. But when I want to show more games, the best thing is cartridges. And … Continue reading

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ZX Spectrum inside CPLD

I found an old ZX Spectrum clone made in Soviet Union in the 90′s. It was my computer, I wrote several programs on it and also, I wrote drivers for Epson printer on this hardware. This model has Soviet chip … Continue reading

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Fancy soldering

Good fellow donated my collection with a new item- Sharp PC-2500. The only big problem- this old computer had caustic batteries inside and they leaked. Alkaline used in the batteries has a very ugly feature- it can travel under conformal … Continue reading

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Testing Commodore 6526/8520 copy in CPLD

There are quite expensive obsolete chip from various Commodore computers and peripherals- CIA/PIA MOS 6526 and a bit changed 8520 used in Amiga computers. This is a “complex” peripheral interface adapter chip for 6502 processor or 68K chipset. It is … Continue reading

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My collection of old computer

For a long time, I collected a small collection of computer hardware. Here is the link to my Old Bits Collection.

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