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We believe strongly that reliance on formulas and equations early in your electronic circuit education is a fine way to prevent you from understanding what’s really going on.

Art of Electronics, Third Edition

Cleaning and repairing ZX Spectrum +3

Got a somewhat cheap ZX Spectrum +3 to my collection. It was marked as untested in eBay ( they usually are ), but I took the risk and bought as the price was ok.  On first test it powered up, the floppy disk was providing sound, TV could be tuned and startup menu appeared. First noticed that some of the keys ( lower part ) were not working. My guess would be that membrane will have to be replaced but anyway, disassembly will show. And it showed. As it more or less was obvious from outside inspection – inside was dirty as hell.

Then, after some cleaning:

I have no CF-2 floppy diskettes to test, so decided to plug in a tape recorder and test some software from and audio cassettes and the i noticed.. that audio jack was missing! It seems that it was just cut away! Found similar one in one my spare parts box and soldered that in.

Also decided that as soldering iron is hot anyway why I would not just make a quick composite mod in the UHF box (using a capacitor). Did that, reassembled it, plugged it in and… yeah – no video.

So, I have undone composite mod, restored everything to original condition and started making RGB to SCART cable for it.