On 10/14/2016 10:17 AM, Francesco Messineo wrote: > On Fri, Oct 14, 2016 at 9:54 AM, Gerrit Heitsch > >> >> If you have a C64 with all MT4264-xx on it and one goes bad, it's a good >> idea to replace all of them, it's very likely that more will go bad soon. > > Maybe, or maybe not. I've never liked to change working parts. > The C64 in that particular video was used almost daily from 1984 to > 1990, then once in a while > from 1990 to 1996 more or less. It will never see much use now, so why > would I change them all? In case of another failure, I can change the > failed chip(s) easily anyway. Yes, you can... But I also do repairs for people who don't know how to use a soldering iron and I had it happen more than once that I changed the offending DRAM and a few weeks later the next one died. Just replacing all MT4264 is cheaper than mailing the system back and forth again. You can use 41256 as replacement for 4164 in a C64 BTW, you only need to add a connection between Pin 1 and Pin 16 of the DRAM. 41256 are easier to get as NOS and are cheap too (less than a Euro a piece). They use 8Bit refresh so there is no problem in the C64. > I've a good collection of failed MOS chips, for some reasons I've > never kept bad chips from other brands, just discarded them (so I > sadly don't have a collection of failed DRAMs). Another kind of chip that doesn't age well are the MOS TTL replacement they made when LS-TTL were in short supply. Especially the MOS 7708 (74LS257) are known to fail now. > I have hundreds of DRAM chips from recycled boards. I think no MTs > among them. Mostly > are japanese (NEC, Fujitsu). I've never found a bad chip among them, > but I test them only > when I need to install a chip somewhere. NEC, Hitachi and Fujitsu are quite good and when they fail they tend to go into meltdown (chip gets very hot) so they are easy to find. > it's a bit like the MOS logic chips, they fail more often than any > standard 74xx TTL chip, but I still have quite a few of them still > working, and I won't touch them as long as they work. Well, if you have a board with a dead 7708 and the other one has the same datecode, better think about replacing that one as well. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2016-10-14 09:00:39
Archive generated by hypermail 2.2.0.