If you currently have 3 DC-DC converter modules for each CPU, I'm afraid all of them are needed for the system to work.
1.) If the OS was running, the suffix of the "model" command would identify the CPU speed in the rp24xx series. But now the system obviously does not run, so you'll need something else. Can you see model numbers on the CPU modules? You might look them up at http://partsurfer.hp.com.
The system model rp2470 actually suggests your processors should be even faster: either 650 MHz or 750 MHz.
2.) If you have a hardware support agreement for your server, you can just let the hardware support people to diagnose and fix this. But if you need to diagnose this yourself, here is one idea:
Do you have another rp2470 you could use to temporarily "loan" a known-good set of power converters from?
You could swap the modules one by one and test each time. Once the problem goes away, the last module you swapped was the faulty one.
I don't recommend removing a CPU if you don't have prior experience on handling the PA-8700 CPU modules: there is a part between the actual CPU and the CPU socket that contains a lot of tiny conductive rubber balls. During use, this gets very hot and often sticks to the CPU socket, so the rubber balls are likely to get damaged when removing the CPU. Therefore, this part is to be regarded as a consumable item when swapping CPUs. (In practice, it's sometimes possible to remove the CPU without damaging the rubber balls, but you must be both very careful and a bit lucky.)
> What happen if i boot the machine with 550 CPU with just one DC-DC Power Converter?
That would be a configuration that is mismatched to the CPU type. You would see the same error message you're seeing now, telling you that the low voltage DC power module is "failed or mismatched to the CPU".
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