Re: Atari Space Riders...

Hi
You stated that the regulator was bad. If it was
shorted, there are most likely a number of bad parts.
As John mentioned, people like to swap the switch
connector with the solenoid connector. It tends to
blow a number of parts as well.
One thing to check is to first remove the switch connector
and rotate both rotory switches to "0". C9 pin 13 should be high
and C9 pin 12 should be low. If not, that will give you a place to
start.
If this fails, it is a good indication that someone tried to swap
the connectors to see if it would work better.
The DMA INT will pulse without or without a working processor. This is
normal.
As John suggested, check that the data lines look like
they are all toggling. Also check C9 pin 6. If there is no pulse
at this point, the processor just isn't running code.
Make sure the reset line ( pin 40 ) of the processor is high.
I've seen cpus fail to run for any number of problems. Could be
bad ROMs, bad RAMs bad CPU, bad address decoders,
you name it. A lot has to work right to keep the CPU happy.
You mentioned that you had hot parts. Which ones are hot?
Do you mean just warm or "ouch" hot. If they are really hot,
it is most likely that they are blown.
The fact that you hear noises from the speaker when probing
means little.
Here is a trick you can used to do a general check of addressing
and the processor. Remove all the ROMs and RAMs. Make
a set of resistors up, such that the data lines D7 through D1
are pulled to zero, through about a 1K resistor. Pull D0 high
with a 1 K resistor as well to 5 volts. Disable the watch
dog timer.
This will allow the processor to run constant NOPs. It will
cycle through the addresses. You should now see pulses
on the select lines to the ROMs and the RAMs. The outputs
of C6 and D1 pulse low. You can also check the address
lines coming from the processor.
With out knowing more, I could only guess your problems.
Dwight

.

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