Vector ROMs - strange copying problem

Now THIS is extremely strange ..............

Regarding the two 2716 EPROMs (positions N/P3 and R3) on one of my Lunar
Lander boards - I can easily make a copy of these (both are HN462716's) and
put the copies into the correct locations on the board, fire up the game
and all works just fine and dandy. Nice display, etc. However, if I then
put the game into test mode, the display is blank although the test runs
just fine (you can hear the four levels of the thrust sound, see the LEDs
blink as they should, etc).

If I put back the original EPROMs then both the game AND the test mode
displays just fine.

Why on earth should I get a blank screen in test mode with these two copied
EPROMs?

I've made various copies onto different makes and speeds of EPROMs but to
no avail. I've tried downloading copies off the Internet and blowing them,
but same problem - game mode is fine, test mode has a blank screen but *is*
working.

I'm certain that my EPROM programmer is copying okay as evidenced by the
fact that I've copied numerous other EPROMs with it over the past few weeks
with no problems whatsoever, and can still copy others for other
applications which work just fine.

Is this a speed issue with the EPROMs, or something more subtle?

Can anyone make any suggestions please?

Thanks,
Phil

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Received on Wed Mar 6 02:14:04 2002