Fix neo geo 4 slot work ram error

[GoodTofuFriday]

version 1 4 slot has the below work ram error. I replaced the sony cxk58257m-12l wram with samsung KM62256ALG-10 which are compatible. Ive replaced both work ram chips with no change and contintuity seems to all be there. Ie also tried with a diag bios with the same result.

Anyone help me out here? Thanks

 

[GoodTofuFriday]

Nothing at all guys?

 

[daskrabs]

Are you sure you replaced the correct chips?

http://www.neo-geo.com/forums/showt...o-RAM-errors&p=2233466&viewfull=1#post2233466

 

[Xian Xi]

Nothing at all guys?

Why did you replace them? That's not what the error is indicating.

4555 means your 13th bit aka D4 on the upper ram isn't reading right, most likely a bad trace.

 

[GoodTofuFriday]

Why did you replace them? That's not what the error is indicating.

4555 means your 13th bit aka D4 on the upper ram isn't reading right, most likely a bad trace.

Looked at the upper work ram on i/o4. It connects directly to an ls174. Is it poasible this is whats bad?

 

[Xian Xi]

Looked at the upper work ram on i/o4. It connects directly to an ls174. Is it poasible this is whats bad?

Are you sure you're tracing the right pin? It should connect to the CPU.

 

[Xian Xi]

To be clear, CPU, Bios and LSPC.

 

[GoodTofuFriday]

To be clear, CPU, Bios and LSPC.

Fairly confident. Second chip from the bottom which im sure is upper work ram. pin 15 which is i/o4 connects to a ls273p

 

[GoodTofuFriday]

Are you sure you're tracing the right pin? It should connect to the CPU.

I did find where it connects to the cpu and the trace is fine. Continuity is there.

 

[Xian Xi]

Fairly confident. Second chip from the bottom which im sure is upper work ram. pin 15 which is i/o4 connects to a ls273p

Both RAMs will connect to the CPU, just remember that the lower RAM will connect to the lower 8 data pins on the CPU meaning D0-D7 and the upper RAM will connect to D8-D15.

And don't forget that it has to connect to everything listed, not just the CPU.

 

[GoodTofuFriday]

double post

 

[GoodTofuFriday]

Both RAMs will connect to the CPU, just remember that the lower RAM will connect to the lower 8 data pins on the CPU meaning D0-D7 and the upper RAM will connect to D8-D15.

And don't forget that it has to connect to everything listed, not just the CPU.

Is there a schematic I can follow? Other than me thinking the z80 might be bad I just cannot find this fault.

 

[GadgetUK]

Is there a schematic I can follow? Other than me thinking the z80 might be bad I just cannot find this fault.

Yes - just search for the MV1FZ schematics (or even the AES schematics that were released earlier) - You can use those to follow connections between RAM and CPU etc.

It's also worth really closely inspecting the board to see if you can find any broken / scratched traces on the top of bottom of the PCB.

 

[GadgetUK]

This post can be deleted - I posted on the wrong thread >.< dumb!

 

[GoodTofuFriday]

So far Ive gone through the traces with a magnifying glass. Ill try looking for that shcematic.