MVS 4-slot issues

[RandomRetro]

Just getting started on this issue but any initial guidance is welcome. When powered on the attached picture is what I see. Is this a common display for a known issue like RAM?

Steps so far:

• Worked without issue for past year
• Checked voltages and all check out
• Tried swapping carts out and around
• Led panels still cycle like on initial boot sequence
• No visible bad traces
• No visible cold/bad solder joints
• No visible battery damage
• No visible puffy or leaking caps

Thoughts to try:

• Swap Bios chip (no luck)
• Recap
• Look with scope for bad solder joints and traces

 

[everten]

Looks like watchdog? Pretty sure Neo will tell you on screen if ram is bad. Could be bad IC or trace damage under an IC. I have 2 MVS boards that look decent on the surface but after removing a chip it was bubbling and rusty underneath.

edit: check here looks very similar

 

[stj]

caps only really effect audio, other than maybe a startup cap to reset the cpu.

you should pull and check the bios, but chances are you have bad ram
just about every neo board i'v worked on had bad ram.

 

[pacoarcade]

I'd say it's caused by something related to BIOS. I got a similar screen from a MV2 without the BIOS installed.

 

[Rom1]

It's a click of death.

Try a diagbios, it involves no skill so it's always the first step for a diag.
Then we'll search deeper.

 

[RandomRetro]

Tested a known UniBios 4.0 and same issues. Going to burn a diag chip and give that a try and then focus in on the probe.

 

[pacoarcade]

If Diagbios doesn't throw any info I'd check continuity between BIOS and M68K. Sometimes broken traces are difficult to notice.