"At the next startup, the processor executed the DESELECT variable from the 2k EEPROM, entered the DESELECT state and was essentially dead. Since the code to get out of DESELECT was removed by QSI at the request of MTH, there is no way to fix the error without replacing the EPROM. "
Yes there is. With a chip that allows you to reset the ID in the EPROM. That is how I clear the boards.
You have far more electronic technical training and education than me, but most of what you said (less the detailed electronic parts) you may have found in some of my former posting on this, and possibly some data from the old QSI website that is no longer available.
Your still missing the most important part which is software versions and subtle hardware changes on top boards. Some ROM chips only work on certain top boards and vice versa. Software was different and there are compatibility issues. Now I don't know where the difference is, but the 3 clanks also shows up when a non compatible chip is used on a top board. It means a software conflict. There are boards that will execute the correct start up sequence and sounds, followed by 3 clanks and no operation. Versus an engine that starts up with 3 clanks. Read my post above a little more closely. C3, C4, C5 top boards. There was a secret squirrel process for changing the software that involved a reset and chip swap while powering down that was never really disclosed by QSI and now that Art Boynton passed probably never to be known. So you can buy a new upgraded version of a chip and find it does not work with your top board. Or you have a bad engine and replace the top board to find it still does not work so you assume the chip is bad. It is not. Need the correct top board.
I am more of a practical engineer. I reversed engineered the repairs to the PS-2 3V board. Tracing all components without the technical education you have. Just treat chips as on and off switches and check valve. Observation of cause and effect. Even removed a few good chips to see what they did. Got to the point I knew more that MTH did on component level repairs. The tech document has a lot of errors and they really only taught audio and speed control. Not lights, battery, DCS signal, Bell/Whistle, Power supply etc...
Interesting diversion, but I imagine folks are more worried about support for DCS engines with PS-2 and 3 then PS-1. There are enough parts out there to fix all the remaining PS-1 engine twice over from all the upgrades. I have about 75 sets worth. Like I said originally it is rare to have to actually replace a board or chip. Mostly bottom board component repair. G
