Hi Brian, Thanks for the detailed explanation. Totally makes sense. My M100s are indeed all the old style PCB that use the non-standard LH* chip. I do wish I was one of those lucky folks with the later model PCBs. One of the reasons I created the Worldwide Model T Registry database on Web8201 was to hopefully build up enough data to understand just how common or uncommon the newer PCB actually is out there!
I had already acquired some of those PLCC packaged EPROMS (yes, with the UV window for erasing) anyway, so was going to try to use the Figtronix setup for my main M100. But I'm contemplating abandoning that idea in favor of Mike Stein's board. On Wed, Aug 23, 2017 at 5:11 PM, Brian White <[email protected]> wrote: > The problem is that the new adapter is too tall for the available space, > if it's plugged in to the original socket. > > The reason it's too tall is because of the plcc socket. Through-hole style > plcc sockets are pretty tall. > > The way that adapter works, you lose the ability to plug the original rom > back in, but but the new rom is removable and rewriteable without any > further special adapters. You just pop the bare chip out and it pops into a > standard reader, with an adapter too, but a standard one that comes with > the reader just to adapte the physical form, notrearrange pins into a > special pinout. > > There are lots of possible work-arounds, but they all have some kind of > down-side just like desoldering the original socket is a down-side. > > You could make a board where the chip is soldered on, and that would fit > in the original socket. > > The problem then is, that chip would not be re-programmable very easily, > because the combined chip-on-adapter creates a non-standard pinout that a > programmer doesn't support. > > You would have to make a "reverse adapter" to ever reprogram later, or get > a test-clip that clips righ onto the chip on the board. > > I *think* it should bebpossible to make an adapter that plugs in to the > original dip socket and still has a plcc socket itself, by using a surface > mount plcc socket instead of a throu-hole one. There is a figtronix option > rom board that uses that. I have made a few and they work. But the > down-side in *that* case is that a low profile surface mount plcc socket > can only be soldered with an oven or hot air and paste. It's MUCH simpler > to solder the through-hole kind for the average hobbyist. I have managed > it, and did it using a cheap $20 hot air gun instead of a $60-$500 "real" > hot air soldering station, but it was tricky and finnicky and not reliably > reproduceable. I also botched it several times and had to keep starting > over. (heat it all up enough to come off, clean off all solder, and start > over very carefully applying new paste and flux and trying lay the socket > in exactly the right position...) > > No mmatter which way you turn, there is either one problem, or some other > problem. > > Mike Stein has a board that uses a full dip chip, and can plug in to the > original socket, but I don't think it can accomodate a socket to make the > new, standard 27C256 removable for reprogramming and still all fit in the > case. If it can, that would be the way to go. Otherwise it's just one of > many equally good-with-a-problem options. > > Remember, this is all only for M100's that have the original non-standard > pinout main rom. Some late M100's and all T102's don't have any problem and > don't need any adapter. > > -- > bkw > > On Aug 23, 2017 5:18 PM, "Gary Weber" <[email protected]> wrote: > >> Hello all, >> >> I have a question for anyone out there who has created a main ROM adapter >> for their Model 100, using these parts and following these instructions: >> http://tandy.wiki/FigTronix#Model_100_Main_ROM_27C256_PLCC_Adapter >> >> My question has to do with this statement: >> "Unfortunately, using this adapter requires desoldering the original >> socket from the motherboard. It IS possible to do this, without damaging >> either the motherboard or even the old socket, with flux, solder wick, and >> patience." >> >> I'm a little confused as to why the original socket would have to be >> de-soldered. Can't this adapter just be plugged into an empty CPU socket? >> Or is it the case that the M100 case can't close again because of something >> so high in that socket pressing against the keyboard circuit-board? >> >> Thanks for the info! >> >> >> -- >> Gary Weber >> [email protected] >> > -- Gary Weber [email protected]
