Re: ms pac voltage trouble

Kev, this answers your question i think...

Honest, in certain circumstances it can (and does) work. It may help that i'm
not so technically minded just yet so i look at it from a more logical point
of view. I don't know all the ins and outs of why maybe it didn't ought to
work, but from a simplistic point of view:

If you stick a good chip on top of a good chip you should see no difference,
both chips will do exactly the same (unless maybe they are different speeds or
something) and you should see no difference in the game. Granted, do it with
the power on, and if it's program ram you'll almost definately crash the
program. Not sure about video ram. Bottom line you shouldn't really do it with
the power on - but surely everyone knows that anyway :)

If you put a good chip on top of a bad chip then at the very least i'd expect
to see a difference. Yes, if it's program ram it may not suddenly make the
program run since the outputs from the chip could affect the good one. Seeing
a difference warrants further investigation in that area, you can be lucky and
find it solves it completely.

So, in the case of the Frogger, i did admittedly have a bit of a head start.
Half the screen was full of rubbish, the other half fine so i knew it was a
video fault of some sort. Powered off, put a good ram on top of one of the two
2114s in the video ram, switched back on, perfect screen. Switch off, remove
it, crap back again.

Bingo, fault found.

Something i always do with things like galaxians and in this case frogger
simply because it's quick and easy to try befor digging even a logic probe or
meter out.

Going back to the original post, i don't know if it will help or not since i
don't remember what the original problem was (and am recompiling my OS so have
no email history), my point was merely if it appears to be a graphics issue,
give it a try it'll take no time. Just be careful not to short anything out or
other.

Something that works for me and now i'll shut up since i've waffled on far too
much already :) YMMV

Regards,
Martin.

John Robertson <jrr@flippers.com> wrote:

> I will have to try that sometime, can't hurt!
>
> Still it might surprise me to see it works, but perhaps if it is a
> bad (open) output on the RAM then your idea would certainly work even
> with static RAM like 2114's.
>
> John :-#)#
>
> At 6:47 PM +0000 3/18/05, martin@guddler.co.uk wrote:
> >Well, it's certainly far from foolproof, but it takes no time at all to
> >quickly do and if your problem is completely solved when piggybacking a
> single
> >IC then it was worth it :)
> >
> >I often find it helpful with logic chips too but that is definately not
> >foolproof, the bad chip often still affecting the inputs and outputs of the
> >good chip. Again, it's quick and it sometimes get's me quick results
though.
> >
> >Martin.
> >
> >John Robertson <jrr@flippers.com> wrote:
> >
> >> Generally speaking that only works with Dynamic RAM that has floating
> >> outputs. I'm surprised it works with 2114s, however it should work
> >> with the Video RAM on the Pacman/Ms Pacman boards.
> >>
> >> John :-#)#
> >>
> >> At 12:26 PM -0500 3/18/05, Electronicamuse@aol.com wrote:
> >> >In a message dated 3/18/2005 8:47:19 A.M. Eastern Standard Time,
> >> >martin@guddler.co.uk writes:
> >> >
> >> >More times than not i find piggybacking each of the 2114's in turn
> >> >with a known good one will reveal which one(s) it is
> >> >
> >> >Do other folks concur that this can be done? I am not looking for
> >> >100$ accuracy, but any fast tips can be of help.
> >> >
> >> >Thanks
> >> >
> > > >Dave
> > >
>
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Received on Fri Mar 18 14:16:06 2005