trs-80 model II trouble

On Tue, Dec 15, 2009 at 10:03 AM, Bob Brown <bbrown at harpercollege.edu>wrote: The space was swapped for a ! because of the stuck bit. So any character that has a 0 in that bit position will be mapped to the character with a 1 in that position, but all the other bits the same. The end result is that half of the characters will be wrong. All the characters with a 1 in that position will be correct. I guess a stopped clock is right twice a day. :-) If they're dips, it's easy. Just don't bend the pins when you put them back in a socket. There's special tools for pulling them out, but you can use a small flat head screwdriver if you're careful. Socketed dip chips have a habit of slowly walking out of the sockets from years of heat expansion and contraction when the machine is switched on and off. It's possible that reseating the chips (just pushing them back into the sockets) will fix the problem. But if they've walked out a bit, it's easier to remove them since a flat screwdriver will fit between the chip and the socket. If they're all the way in, i've used an exacto knife to get between the chip and socket before. Just don't break off the blade. Try to get the chip to come out straight, that is work both ends of the chip. Otherwise, the pins will bend when you take it out. Oh, and don't put them in backwards or they'll fry. They'll get hot enough to burn you. So note the orientation before taking them out. Also, I've received new chips (back when I routinely installed cache chips on 486 motherboards) where the pins sort of splayed out a bit. This made them not line up with the sockets quite right. You may need to bend them so that they're slightly more upright making them line up with the holes in the socket. This is easier than it sounds. brian