This is an old post, preserved for reference.
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Here we have the classic Atari 2600 Video Computer System. This is a six switch model from 1980 and is suffering from the good old black screen problem. That covers a variety of problems, from nothing at all being output to a correct video frame being generated, just with nothing on it.
7805 regulator replacement on a ZX Spectrum Plus). This 2600 draws about 350mA in operation. So at 9v input, that is (9-5)*0.35 = 1.4 watts. The heatsinks probably equates to something like 20°C/watt, so they will end up 28°C above ambient, not too much of an issue. Given this one is working, no need to do it here. The ZX81 with a RAM pack is two or three times that and becomes noticeably hot, and so is worth doing on a ZX81.