Re: Gottlieb RAM question

OK, three weeks later and I finish my experimenting. I robbed one good MK4801 off
another Gottlieb board so I can test a single 6116 instead of two and doubling my
potential problems.

I lifted pin 19 and tied it to +5 (pin 24 of the 6116). Didn't work.
Tied pin 19 to GND (pin 12 of the 6116). Didn't work.
Tried Roger's suggestion of tying pin 19 to another select line (pin 23 in this case)
- still didn't work.

At this point can I safely assume the Gottlieb board doesn't like the extra 8K in the
6116? Suggestions?

tom

solarfox@texas.net wrote:

> On Sun, 13 May 2001 20:01:35 -0500, you wrote:
>
> >Quite interesting. So the MK4801 was the cheaper alternative to a 16K ram - even
> >though it was technically the same chip. Hmm.
>
> Not at all uncommon - and actually, the MK4801 was an alternative to an
> 8K RAM, not a 16K RAM, since half of the matrix was defective. :)
>
> >Well, I took a look through some Gottlieb schematics, and it seems that both 4801
> >SRAMs have pin 19 labeled as "L" with a bar over it. Am I assuming correctly that
> >this means logic Low?
>
> Afraid not... it means a signal called "L-not"; i.e. a signal called
> "L", which is active when low instead of high. What "L" means is anyone's
> guess, unless you have the data sheet...
>
> >Following the traces on the board, it appears each pin is connected to another
> >device (the schematics only show a connection to a resistor). I know I'm showing
> >my ignorance, but would I lift pin 19 on these 6116 RAMs and still have a
> >functioning external circuit?
>
> Lift pin 19 on the 6116 chips _and_ tie it either to ground or to +5
> through a 10K pullup resistor. (Tie each one separately; don't connect
> them all to one pullup.) Don't leave it floating, or signal noise will
> make the 6116 keep flipping back and forth between the two 8K banks
> randomly.
>
> -----------------------------------------------------------------------------
> "There is no virtue in suffering fools gladly, for it only encourages them to
> persist in their foolishness." --Kehlog Albran
> -----------------------------------------------------------------------------
> solarfox@DON'TMESSWITHtexas.net (Gary Akins jr.)
> http://lonestar.texas.net/~solarfox
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Received on Thu Jun 07 22:53:59 2001