Re: derkom's attempt
Posted: 03 Dec 2019 19:00
Okay, I have good progress to report. Not success yet, but it seems within reach.
First today I reflowed all the PLCC chip sockets, MFP, and all the RAM, and what do you know, the bus errors went away. I could see on the logic analyser that the system appeared to be running properly. One bus error on startup, followed by zero bus errors and plenty of activity on all address lines. Plugged in a keyboard and sure enough, a floppy LED! However, still just white screen video and no diagnostic cartridge output on serial.
So I reflowed pretty much everything else on the board, hoping that my video and serial issues might go away, but to no avail. Still white screen, still no diagnostic cart on serial. I should note that the serial chip I'm using is also pulled from Atarian Computing's Alpha board and is not known to work, although there is no reason to believe it wouldn't. When I ordered all my items from Mouser, they didn't have any of the MAX238s in stock. I ordered one on fleabay, but it has yet to arrive.
So, what is one to do with an ST with a floppy LED and no video output to confirm things are running? Why, hook up a floppy drive and try out an autobooting game of course! I soldered on the floppy connector, attached a floppy drive, and popped in a copy of Lotus III and turned it on, and sure enough, it runs the game. Still no video of course, but this certainly confirms that the system is indeed running.
Suggestions for diagnosing the video and/or serial issues are welcome. I figure I can look at the appropriate YM2149 pins to see if anything is being sent over to the MAX238. Don't have a clue about tracking down the video stuff. I sure hope I haven't cooked any of the SMT stuff, because I do not look forward to doing that again.
First today I reflowed all the PLCC chip sockets, MFP, and all the RAM, and what do you know, the bus errors went away. I could see on the logic analyser that the system appeared to be running properly. One bus error on startup, followed by zero bus errors and plenty of activity on all address lines. Plugged in a keyboard and sure enough, a floppy LED! However, still just white screen video and no diagnostic cartridge output on serial.
So I reflowed pretty much everything else on the board, hoping that my video and serial issues might go away, but to no avail. Still white screen, still no diagnostic cart on serial. I should note that the serial chip I'm using is also pulled from Atarian Computing's Alpha board and is not known to work, although there is no reason to believe it wouldn't. When I ordered all my items from Mouser, they didn't have any of the MAX238s in stock. I ordered one on fleabay, but it has yet to arrive.
So, what is one to do with an ST with a floppy LED and no video output to confirm things are running? Why, hook up a floppy drive and try out an autobooting game of course! I soldered on the floppy connector, attached a floppy drive, and popped in a copy of Lotus III and turned it on, and sure enough, it runs the game. Still no video of course, but this certainly confirms that the system is indeed running.
Suggestions for diagnosing the video and/or serial issues are welcome. I figure I can look at the appropriate YM2149 pins to see if anything is being sent over to the MAX238. Don't have a clue about tracking down the video stuff. I sure hope I haven't cooked any of the SMT stuff, because I do not look forward to doing that again.