Thanks to everyone who responded to my "6507 pin description" problem.
I tied pin 1 of the 6507 directly to +5v, jumpered from pin 20 of the TIA
I tied pin 2 directly to ground
When I cut out a section of the PCB, a chunk of metal on the PCB got
isolated from the "main ground". When I connected this "metal island" to
the main ground, the Atari finally started working.
I discovered this when I checked the output voltages of the cartridge port.
Instead of +5v, it was reading +2v. The grounded lines of the cartridge
port end up being connected to this "metal island" that I mentioned before.
The cartridge port was never TRULY grounded.
I know my direct jumpering of the 6507 probably isn't the healthiest way to
do things, but it works. Does anyone predict any possible future problems
with fixing things this way?
Also, I've taken a look at the composite mod in the 2600 faq. Is it just
me, or does this circuit use WAY too many resistors? I can understand why
the resistors for the LUM lines are needed, but why all the intricate setup
of resistors connecting +5v to ground?
The circuit mentions using the CD4050 chip to buffer the luminance lines
because the LUM lines on the TIA chip are "open collector". Does this mean
that all collectors on a transistor gate should be properly grounded
somehow?
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