TECH: Ram test help request

Archived from groups: rec.games.video.arcade.collecting (More info?)

Maybe someone can help me. I have a Space Encounters arcade cabinet
which I am trying to revive. I have verified the motherboard PCB and
daughter board are receiving the appropriate power supply levels.

I have some new 2107 Ram replacement chips which I just received and
am trying to locate which Ram chips are bad. I am trying to do this
by setting the DIP switch settings to "RAM test" and then placing one
new Ram chip on top of each of the 16 existing non-socketed Ram chips
on the motherboard PCB. I was hoping this would tell me which Ram
chip was bad by eventually displaying the nice RAM test display on the
monitor, however, this never occurred.

I actually tried every combination of one new RAM chip piggy-backing
the exist RAM chip as well as even combo of 2 new RAM Chips
piggy-backing two existing RAM chips. No luck.

The following are pictures of what I am seeing:

1) This shows what I see when the RAM test DIP switch IS NOT on when
the cabinet is powered on.

http://unclet.arcadecontrols.com/SpaceEn/myRamTestDipOff1.jpg


2) This is what my monitor fades to every now and again while the RAM
test DIP switch IS NOT on.

http://unclet.arcadecontrols.com/SpaceEn/myRamTestDipOff2.jpg


3) This shows what I see when the RAM test DIP switch IS on when the
cabinet is powered on.

http://unclet.arcadecontrols.com/SpaceEn/myRamTestDipOn.jpg


4) This shows what I see when the RAM test DIP switch IS on and one of
my new RAM chips is on one of the old non-socketed Ram chips on the
PCB.

http://unclet.arcadecontrols.com/SpaceEn/myRamTestDipOnWithNewRam.jpg


Any help with what I should do to resolve the problem as to why I can
not see a nice game image would be nice.....


QUESTIONS:

a) Are my Roms bad (based on the images ... if you can tell)?

b) Can I simply piggy-back all 16 socketed RAM chips with 16 new 2107
replacement RAM chips all at the same time?

c) Am I damaging my PCB or RAM by piggy-backing RAM chips?

Thanks
UncleT
3 answers Last reply
More about tech test request
  1. Archived from groups: rec.games.video.arcade.collecting (More info?)

    Piggybacking is only 50% of the game. If one of the rams has dead line,
    piggybacking it will bring that line back up.. if the line is stuck
    high on the other hand, no matter what you piggyback onto it there is
    still a gate inline that is stuck high and whereever it leads will
    continue to see a high line.

    Let me ask you this. does that game play blind? have you verified the
    cabinet voltages and reset line?
    for the ram test you are to pull the ROM at location H and if that
    doesn't get you good lines pull them all.

    then we go to the next step when you come back with those answers.

    Alex yeckley.. it's your turn :)

    - Matt
  2. Archived from groups: rec.games.video.arcade.collecting (More info?)

    I sent you some email ..... or if you prefer and I can post my
    findings here instead ...... Let me know.

    Regards,
    UncleT


    On 10 May 2005 16:43:25 -0700, "Matty-t" <matthews@audio-doctors.com>
    wrote:

    >Piggybacking is only 50% of the game. If one of the rams has dead line,
    >piggybacking it will bring that line back up.. if the line is stuck
    >high on the other hand, no matter what you piggyback onto it there is
    >still a gate inline that is stuck high and whereever it leads will
    >continue to see a high line.
    >
    > Let me ask you this. does that game play blind? have you verified the
    >cabinet voltages and reset line?
    >for the ram test you are to pull the ROM at location H and if that
    >doesn't get you good lines pull them all.
    >
    > then we go to the next step when you come back with those answers.
    >
    > Alex yeckley.. it's your turn :)
    >
    > - Matt
  3. Archived from groups: rec.games.video.arcade.collecting (More info?)

    post it here.. that way there's a record for others who may have similar
    problems...

    "uncletr" <uncletr2@bellsouth.net> wrote in message
    news:3ba5815h1klganivk1sp4hohpnger25i3v@4ax.com...
    >I sent you some email ..... or if you prefer and I can post my
    > findings here instead ...... Let me know.
    >
    > Regards,
    > UncleT
    >
    >
    >
    > On 10 May 2005 16:43:25 -0700, "Matty-t" <matthews@audio-doctors.com>
    > wrote:
    >
    >>Piggybacking is only 50% of the game. If one of the rams has dead line,
    >>piggybacking it will bring that line back up.. if the line is stuck
    >>high on the other hand, no matter what you piggyback onto it there is
    >>still a gate inline that is stuck high and whereever it leads will
    >>continue to see a high line.
    >>
    >> Let me ask you this. does that game play blind? have you verified the
    >>cabinet voltages and reset line?
    >>for the ram test you are to pull the ROM at location H and if that
    >>doesn't get you good lines pull them all.
    >>
    >> then we go to the next step when you come back with those answers.
    >>
    >> Alex yeckley.. it's your turn :)
    >>
    >> - Matt
    >
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