I will add after each IC what it does...
Quote:
Originally Posted by Sean Williams
Righto, Power supply now repaired - a 5v regulator had decided to act as a short circuit.
A list of "Big" ICs on each board.
CPU Board
D8251AC - USART -- serial chip, maybe serial port to the line
D8259AC - Interrupt controller
D8253C-5 - Counter.timer -- maybe used for baud rate generation as the 8251 doesn't include that function.
Program Eprom
Printer Drive Board/Decoder Board
D8243C - I/O expander for the 8048 family. More ports to drive motors, printhead,etc ?
D8741AD - Slave microcontroller
D8039HL - ROMless microcontroller.
2 Eproms - For the 8039 I guess
Is this another PCB?
D8259AC - Interrupt controller
D8251AC - USART serial chip
D8243C - I/O expander for the 8048 family
D8253C-5 - Counter timer -- again maybe baud rate generator for the 8251
D8039HL - ROMless microcontroller
1 Eprom - Firmware for the 8039 I guess
Keyboard
D8039HL - ROMless microcontroller
22-950-38 - I think that's one possible interface chip for a Keytronics capacitive keyboard. How many pins?
FX1 059 - No idea, How many pins?
1 Eprom - firmware for the 8039
There are also 2 memory boards - from the description of the German machine that is similar, these two cards are only used for message storage functions, so as far as I can tell these will have little bearing on the basic start up of the machine.
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Unless there's RAM on one of the other boards, I would assume it needed at least one good memory board to start up.
I think if it were mine I would now consider tracing out the full schematics. It will take a long time, particularly if you are not used to doing it, but then you would know what is going on and how it should work.