RE: Major Havoc help (was: Vectrex on Vector Monitor?)

> >quit reading it after arguing with some twit for far too long about
> 6809
>
> "twit" huh? Not very nice :)
>
:-) *grin* I probably should've put a smiley in there, but I was
typing fast before a meeting... ;-)

> Speaking of twits, I have a couple MH boards I would like to resurrect
> from the grave. Board repair is not my specialty, but I have the
> capabilities to do it. Anybody have some tips/Atari signature guide/
> anything to help me with this task?
>
What kind of problems are they exhibiting? I've had good luck fixing
vector boards just starting at the crystal and tracing through the game
with nothing fancier than a logic probe. (A LOT of vector boards are
"resurrected" just by replacing a dead crystal, IMHO.) Just step
through it logically:

Is the clock running? (check crystal and clock on microprocessors)
Is the board coming out of reset? (check watchdog outputs and reset
pins)
Does it look like the processor is running? (check datalines and address
bus for activity)
Is it doing something useful? (see if chip selects on multiple ROMs are
occuring)
Is the Vector generator running? (check the signals in the vector
generator-- "GO, Reset, etc." is it hitting the Vector generator ROM?
Is the vector generator ASIC good?)
Are the DACs getting input data?
Are the DACs generating output voltages that make sense?

I find the majority of problems in the clock circuit, followed by the
vector generator (usually after the DAC outputs), and then the program
ROMs....

-Clay
Received on Wed Aug 12 12:57:52 1998