24c04 on 550 backplane

[rickhunter]

In the old forum there was a post regarding an issue running G+ CPUNXT games on a conversion.  It boiled down to a problem with the 24c04 chip that was on the backplane.  It is not regarding G+ games, but games that use a specific OS card.   Recently I've run into a similar problem and I've tried 2 brands of 24c04's.  The original poster found  the solution to be using a specific type of 24c04, and I'm trying to see if it will work for me.  Does anybody remember the topic?

My issue is that on 2 of my 3 backplanes (and I've actually pulled the backplanes independently and confirmed this issue) the  game works as it should.  On the 3rd backplane, the boot process just aborts with a "file not found" type error.  These backplanes just have some resistors and about the only "active" part is the eeprom.  I have switched the eeprom with ones I purchased for S+ repairs, but I get the same sympton and I don't want to go a desolder one from a working game.  Is there a known difference between 24c04's?  The ones on the two working boards are 24c04P, the ones I have as spares say 2404a.

[uniman]

Found this post, maybe it helps?

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.
 

[cfh]

Is there a known difference between 24c04's?  The ones on the two working boards are 24c04P, the ones I have as spares say 2404a.

I would say "yes" there is a difference. The "P" means plastic case.
that does not matter. but the "C" is for CMOS, and that does usually
matter. I would order some from Mouser (they are cheap) with the
"C" code.

[KirkLasVegas]

The problem with CMOS is the drive current available at a "Node". usually limited to 10 Ma. A CMOS chip can not drive another chip unless it's also CMOS (4016/4066 are the exception) and a TTL chip will pull down a CMOS output...

In other words..the "C" is VERY important. A 24C04 is differant than a 2404, much power power in and out.Same rule applies to 27C256 VS. 27256

See pictures...both are 27256 EPROMS..one is 27C256 the other 27256 *NOT* the same

Hope this helps...

Kirk

[rickhunter]

That was not the correct post.  It starts like this as found on google, but they don't have the page cached anymore 

CPUNXT HELP
I am trying to run some of the knew G+ games in a 550 and NXT board, with filter and auxilery cable installed. All of the games get past the signature ...


I do have 24c04, but I'm pretty sure the orignal poster found a solution by buying a specific 24c04.

[StatFreak]

That was not the correct post.  It starts like this as found on google, but they don't have the page cached anymore 
...

I noticed that the google cache links for the old site are no longer returning results. 
However, technically, they do have the page cached, they've just taken it off the menu.