PS3 PS3 DIA-002 – Cell OC causes no video output!

[manuki]

Hi everyone,
I'm having a strange issue with overclocking the Cell on my PS3 and I'm running out of ideas where the problem might be.
Setup

• Motherboard: DIA-002
• UART: 100% correctly wired and confirmed working
• Console works perfectly on stock clock values (FF for Cell)
• RSX overclock works without any issues
• Cell undervolting works correctly

The problem

I've tried multiple times to overclock only the Cell, without touching XDR. Even a minimal OC from 3.2 GHz to 3.3 GHz (Cell only) results in the same behavior.
The console powers on normally:

• Green LED turns on
• No YLOD
• No shutdown

However:

• No video output at all
• Controller does not connect
• No characteristic yellow LED flash from webMAN at boot
• Resetting video output does nothing

I also tried booting and monitoring through UART. There are no visible errors in the logs (screenshot) - nothing indicating a crash or panic. I'm attaching the logs for reference.
What's interesting:

• After failed OC attempts, I reverted Cell clock values back to FF and the console boots normally again.
• Undervolting works perfectly fine.
• RSX overclock works perfectly fine.
• The issue happens even with the smallest possible Cell-only overclock.

So the board is stable on stock clocks, stable with undervolt, stable with RSX OC, but completely refuses any Cell frequency increase.
Question

Where could the problem be?

• Is this typical for some DIA-002 boards?
• Could it be related to XDR timing even if I'm not modifying it?
• Could this indicate a weak Cell that simply cannot handle even a minimal frequency bump?
• Is there anything else I should check on UART logs specifically?

Any ideas or similar experiences would be greatly appreciated.