Re: Re[2]: Millipede to JAMMA? Anyone?

On Wed, 23 Nov 2005 18:55:42 +0300, you wrote:

>> I do have the resets hooked up as required, so Im a bit confused as to
>> why its not working :-(

>2 - millipede uses an eerom, so it probably needs 12v connected to some 14.5v
>transformer input or something - check the schematics. i had this problem
>starting a starwars on the scope so it's probably the same.

        Millipede requires the +22Vdc and -22Vdc supply rails from the ARII
board in order to generate the -28Vdc programming voltage for the EAROM...
but unless I'm missing something in the ER2055 EAROM's data sheet, all that
will happen if the ER2055's negative VEE supply is absent is that the
ER2055 can't successfully do a write cycle. The board should still boot
without the +22V/-22V supplies; it just won't save high scores.

        However -- looking at the Millipede schematics, I see two things you
should check:

(1) The board will not come out of power-on reset until it gets the 10.6Vdc
(unregulated) voltage from the power supply. Do you have anything tied to
pin "E" and pin 18 on the Millipede board? If not, try connecting it to
+12Vdc from the JAMMA harness. (Since the original voltage supply was
unregulated, and the TL082 op-amp driven by it is rated for supply voltages
up to 36V, the board shouldn't have a problem with getting a regulated +12V
on that line.)

(2) The +22Vdc supply is _required_ for the video outputs to work, because
the final output stage of each color is a single-transistor amplifier that
runs off the +15V which Millipede derives from the +22V input. (The +22V
goes through an LM7815 regulator, so just hooking +12V to pin 3 on the
Millipede board won't be good enough; the input voltage to an LM78-series
regulator needs to be at least 1.5V higher than the rated output voltage,
if memory serves.)

-----------------------------------------------------------------------------
"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
-----------------------------------------------------------------------------

---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com
Received on Wed Nov 23 21:54:36 2005