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Namco ND-1 board - Namco Collection vol 2 with ISSUEs

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iTRDC2

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Hello all,

I have a faulty Namco ND-1 PCB (with Namco Collection vol 2).
When I turn on the arcade, the board does the RAM test and it passes that test, then it does the SUB test and after that the board reboots and keeps doing that (it is in an infinite loop).

I already tunned the Power supply 5 volts according to the manual and it did not solved the ISSUE.
The board does not have any visible bad traces.

I researched a bit and found that the SMD electrolytic capacitors have tendencies to leak or malfunction and that can cause video and sound ISSUES.
Nevertheless I did not found any information about the infinite loop ISSUE that I have.

Anyone have any idea of what can be the root cause?

Thanks in advance and happy gaming.

BR,
iTRDC2
 
It's not completing SUB CHECK.
If OK, it should display "SUB OK".
If not, it should display "SUB NG" and spin forever.

It shouldn't reboot like that. The routine that does the SUB CHECK communicates with the NAMCO CUSKEY CHIP which (also) handles protection.
I _might_ be able to narrow it down further looking at the code.
 
tcdev said:
It's not completing SUB CHECK.
If OK, it should display "SUB OK".
If not, it should display "SUB NG" and spin forever.

It shouldn't reboot like that. The routine that does the SUB CHECK communicates with the NAMCO CUSKEY CHIP which (also) handles protection.
I _might_ be able to narrow it down further looking at the code.
Click to expand...

I did not found a fix for this yet. How do you have access to the code?

BR,
iTRDC2
 
iTRDC2 said:
I did not found a fix for this yet. How do you have access to the code?

BR,
iTRDC2
Click to expand...
I don't have access to any source, just my own reverse-engineering (disassembly). I'm actually looking at implementing it in MiSTer atm, and have cracked open the code to look at a few of the details for the configuration of the video timing in the graphics processor - YGV608 (8C).

One of the first things it does is feed the entire 68K program ROM (13D,14D) into the CUSKEY, which presumably must be happy with the contents before it proceeds. Unfortunately the schematics aren't readily available but I'd guess the CUSKEY is able to reboot the system (directly or otherwise) if it's not happy, as it is responsible for the protection functions. Whether it does that immediately, or after a delay just to make things harder to hack, is anyone's guess. This is likely the reason you can't run Vol 2 ROMs on a Vol 1 PCB, aside from the issue that the (SMT) graphics ROM will be completely wrong.

It's a difficult one to debug without a logic analyzer on the address & data bus to see exactly where the 68K gets interrupted. The fact that it reboots suggests to me it's something to do with CUSKEY, but it could be a few things... schematics would be nice!

An aside - have you seen this? Unfortunately your board doesn't get far enough in the boot process...
Namco Classics Debug routines
 
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