David Savery <
djsa...@gmail.com> wrote:
> The screen works just fine, the sound works, the cartridge slot
> identifies the game loaded in, but on power-up I cannot get (and
> have never seen) the menu, and any game comes to a stop at Player
> 1 immediately after the requisite title screen. This happens
> whether the controller is plugged in or not. That it can read
> carts, play into tunes and display legible information about the
> game before coming to a halt means, I assume, that things like
> the processor and timing are good.
>
> Does anyone have any experience of this kid of fault or any
> suggestion of where to go from here? I've been scouring the
> interwebs and I've found suggestions that the AY-3-8912 could
> perhaps be responsible. I still have two Amstrad 464's in the
> loft - I'm wondering if I should crack one of those open for some
> donor parts as I believe they used the same chip (and may even
> have one in a DIL socket for easy extraction), but I thought I'd
> ask here in case someone had any information that might save a
> wild goose chase!
Holding down controller buttons at the game title screen and not
releasing them seems to have this effect, so the theory about the
AY-3-8912 would be that, as the chip that reads the controller
buttons, it's reading one as pressed down all the time and that
prevents the game from starting. Swapping it over seems like a
good starting point. Another possibility is that one of the
capacitors (C214 - C221) on the logic board that connect to the
controller input signals has shorted. Check the resistance over
them with a multimeter.
Finally, it could also be an issue with one of the address signals.
In that case, given that it happens with both cartridges and
Minestorm, that would most likely be a problem with the 68A09 CPU.
That might better explain the problem you had before with not
seeing "PLAYER 1" at all, because there was an address signal issue
which made the game jump ahead of that part. It could also be that
a faulty AY-3-8912 used to always pulse button 4 during start-up,
but odd that the same behaviour wouldn't continue once the game had
started.
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