Trying to fix Agilent n5181a - Error 508 frac-n loop unlocked

[DavidAlfa]

No obvious damage, the instrument always boots with this error, defaulting to 3GHz -110dBm.
Nothing comes out of it at any frequency or power.

There's no schematic and the service manual just says "Instrument may need servicing".
The lowest the service manual goes about this is : "Replace RF assembly".

Based in the available info from other models, this seem a frequency synthesizer error.
Found the 10 & 100MHz reference clocks, they seem healthy.

The board is huge, has thousands of parts and there's no silkscreen, would appreciate any info shedding some light at this.

I'm pretty sure circuits will be very similar to other models, but again zero schematics found.

Found this E4400B thread having the same issue:
https://www.eevblog.com/forum/testgear/a-look-inside-of-an-agilent-e4400b-signal-generator/

Linking to this board:
https://groups.io/g/HP-Agilent-Keysight-equipment/topic/synthesizer_module_in_esg/28079593

Tomorrow will check if this model has the problematic 1GC1-4210 ICs.

Thanks!