From Newsgroup: rec.games.pinball

Am 23.01.2025 um 17:00 schrieb John Robertson:

On 2025-01-09 5:03 p.m., Jan Ernst Vo|f wrote:

Thanks for your replies!

To say the truth, i am not really new to this group, but that's been
more than 30 years ago.

Over the time, i owned 67 pinball games, all of them but the first
one, a Gottlieb's "Super Soccer" had failures. I've searched the
"Super Soccer" about a zillion to find the bad zero switch at the drum
units. I was 15 at this time, now i'm 62 years old.

I repaired more than 100 machines, EM and SS as well.

But games build by Playmatic are special: they use CMOS instead of TTL
logic.

I bought a Big Town in 1987. The price was cheap, 70 DM (around 35$).
Both RAMs, both ROMs, and the CPU were dead.

And other chips on the MPU were dead. I was able to get another
machine month later. It had good ROMs. This game was cheaper, 50 DM
(around 25$). I build a small circuit, using just 8 IS to do the job
of the 1834 ROMs.

The ROMs were replaced by an EPROM 2716. The game went in attract mode
at once. Both games had a bad 74C42 on the decoder.

Due to my job, i know most assembly languages of former machines. The
knowledge about these, i've made a "diagnostic board" for the
Playmatics, which was very helpful to find errors in the MPU of the
games.

Now I have 2 bad "Big Town". Both are faulty.

1) Does not recognize contacts other than the coins, the credit, the
ball resting, reset, and the test buttons.

2) Shows irretating scores. "20" is the high score to date, new games
start with 200.020 points.

That's it.

Kind regards,
Jan

Hi Jan,

Wow, that is an unusual MPU and wiring diagram for we North Americans!
I'm going by manuals and schematics I downloaded from ipdb.org - specifically Antar for the theory and schematics and Chance for the
overall MPU diagram.

The Antar schematic shows that the switches that are working share a
common return line (page 24 of 35 in download Antar manual PDF) - so I suspect that you have an issue with other returns - and a logic probe
that is happy with CMOS should help here.

And as for the '20' on your display, I assume you have tried clearing
the 5101 CMOS RAM (disconnect battery overnight - worst case clear), so
it may be time to find a replacement RAM that is known-to-be-good.

John :-#)#

Hi John,

first of all: a happy new year and so sorry for the endless delay.

These machines have no 5101 but 2 RAM's 1824, one of them powered by an electronic capacitor. The games have no batteries. I guess, now the
stand to long. They reach the attract mode, but there is no reaction to
any switch. I hate these machines, but can use their playfield glasses
for other games. I have a "Four Seasons" (Gottlieb) and a "Banzai Run" (Williams). Both of them are easy to repair and are in need of new
glasses for their playfields.

So, thanks a lot for your patience and sorrow for my awful english.
Kind regards, Jan.
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