Neo 2 Slot issue

[alphagamer]

I get the following error on a Neo Geo 2 Slot system:



Backup RAM error
-ADRS- -WR- -RE-
00D00010 5555 55FF


I got my multimeter out and tested all the traces, without luck so far (all traces seem to be good).

What else can I test? How can I verify the chips are working correctly?

Even funnier: With a Unibios I can force the system to boot, but the only setting that boots games is JAPAN - ARCADE.

[Twimfy]

I get the following error on a Neo Geo 2 Slot system:



I got my multimeter out and tested all the traces, without luck so far (all traces seem to be good).

What else can I test? How can I verify the chips are working correctly?

Even funnier: With a Unibios I can force the system to boot, but the only setting that boots games is JAPAN - ARCADE.

How many games have you tested on this unit? Back up Ram would suggest a game error.

[alphagamer]

It is the same with all my games, that is not it.

I get the same error when no cartridge is inserted.

[Calpis]

The /OE signal (which on the Neo is a fully decoded read) is broken on the low byte chip, check both to figure out which one it is.

[alphagamer]

Thanks! You mean the CXK5864BSP-10L, right?

They should connect to the SNK CORP LSPC2-A2... damn, I need a fine soldering iron for that 176pin chip.... I only have a hot screwdriver right now....

[Calpis]

No not at all! The 64 kbit chips are palette RAM.

I was wrong about the backup RAM being fully decoded, only WRAM is, so /CE must be checked as well.

The only way to check continuity on these chips is to trace the signal back to the ASIC it came from, and that could be difficult without a schematic since it could require desoldering SMT chips. If your model has the NEO-C1 chip though, I know the approximate pins from a bad schematic.

First, find the "43256" chips near the battery, the specific chip code will change. Next, find the chip that is connected to 68K pin 64 (top right pin), this is the problem chip.

From there note the pins :
RAM pin 20 - /CE - connects to the nearest 74HC/LS32 pin 11
RAM pin 22 - /OE - connects to the nearest 74HC/LS32 pin 6
RAM pin 27 - /WE - connects to NEO-C1 pin #7. It's either 27,37,57,87 or 97, I can't tell.

If all those are fine, you have to trace from the 74HC32 back to the NEO-C1 which is more difficult. For that look at 74HC32 pins 1,2,5. If THOSE aren't the problem, then you have a problem with the battery circuit and probably should send it to someone.

[alphagamer]

Thanks. I owe you a beer.

Looks like I will have some fun with this tomorrow, but first I need to get some proper equipment.

[l_oliveira]

I've repaired a lot of MVS units with that issue ...

The SANYO/Maxwell-Hitachi MnO2-Li rechargeable battery leaks a lot less than those YUASA or similar NiCd batteries (similar to what was used then on 386s and 486s for rechargeable CMOS battery) you find on the early Neo Geo units ...

But then once in a while I get an newer unit with a MnO2-Li leaked battery (damn it's gooey) :DOH:

A great tool to test the rest of the system is Razoola's Unibios. :thumbsup:


Edit:

Make sure you check the battery for leaks !!! And if it leaked, make sure you neutralize the acid !
(got carried away and forgot that this is what I meant to say when I hit the reply button lol)