Gerrit Heitsch writes: > On 2/22/25 18:28, Francesco Messineo wrote: >> >> I've never seen a good 8501 in my whole life so far. I have made a >> replacement for it with a 6502 and 2 x ATF1502 CPLDs, this is barely >> larger than the 8501 itself. But I only have one C16 that was donated >> many years ago by a friend. > > The 8501R4 or 8501 without R-Number seem to last. I have a few of them, a > few years ago a number popped up on ebay for a low price. > > I still have working 8501R1 too. > > My 7501R1 failed though. > I have for at long time been wondering if the high number of failing 7501/8501's is simply due to "bad" design of the C16/Plus4... The 7501/8501's are connected directly to the serial port. When connecting a serial cable between a drive and computer (both turned on) - there is no gaurantee what so ever - that GND in the cable is the first to connect - that missing ground connection would as far as I can see result in a huge potential difference between the connecting units. A potential that easily could blast some gates in a 7501/8501 (I'm guessing here) PS: please observe any USB cable - there have been put a lot of thought into that design - ensuring that GND is the first connector to "touch base" On the C64 most of the serial port pins are routed to the CIA2 - and I believe that we all have seen lots of dead 6526's... Both C64, C16 and Plus/4 have dtape/atasette pins routes directly to the C2N port - but the difference here is that the 1530/1531's are not separately powered - that means no difference in potential when connecting to a unit that is powered on.... Theory: So maybe the 7501/8501's aren't as that bad as their reputation - it just comes down to them being used in a "bad" design... Any thoughts about this theory ? /UffeReceived on 2025-02-22 20:00:11
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