Model 40x Wms: dreaded Fail LED and 24C04 backplane chip - repost

[cfh]

reposted from original NLG site...

So i'm working on a bunch of Wms dotmation machines, got from a guy
that i suspect kind of gave up on a bunch of them. But anyway, this
Pharoah's Fortune is the problem.

Test the I/O board in another machine, works great!
Test the processor board in another machine, works great!

But in the Pharoah machine, after about 3 seconds of boot time,
the Fail LED comes on. All voltage good and all power LEDs
are on (using a computer power supply by the way).

So what's left? not much! try disconnecting just about everything.
Only leave the Power, Coin Validation/chute and Game Button
connectors on the back panel. Same thing, Fail LED on.

So i take another backplane board from a junk machine,
plug in the Power, Coin, Button connectors and the I/O
and processor board. BINGO!  Game comes up.

So what's up with this? well it's the 24C04 chip (8 pins)
on the backplane board (heck it's the only component on
the board!) This is a serial EPROM 4k in size (512x8).
This is the same technology that IGT uses on their S+
machines (when you have a bad motherboard on an
IGT, this is the component that goes bad).  These are available
from Mouser.com part# 511-M24C04-WMN6P, 46 cent each!
Stock up now, before they go obsolete. Though
I've never seen a bad one on a Wms slot (just IGT), but
i guess it figures.

But the way, getting that backplane board out of a Wms
game is a bitch. you have to remove the reels and undo
four nuts that hold the board tray in place. it's difficult to
get to those four nuts!

Anyway, i thought this may help someone.