E4438C ESg Vector Signal Generator Repair FRAC N Module

[Uselesss]

Hi guys,

I was able to loot an Aligent E4438C ESG generator from the scrap container.

At least the Fractional N module of this one is defective and somebody made it rather worse during the repair  .

Up to 250 MHZ the generator delivers a much too low output power, which is independent of the set power, and above 250 MHZ it delivers no signal at all.
An IC U310 shortly before the output of the Frac N module was replaced by a dual gate MOSFET.
As you can see on the photos.



The self-test shows this:





Can anyone tell me what a U310 component is? Maybe this could solve the problem and if not I can still learn something.

Do you know a simple trick to build an extension cable for the digital pins so I can measure in the open circuit?

For measuring I have an oscilloscope and a spectrum analyzer.

Many thanks in advance

P.S. sorry for not using the tumpnails for the pictures but some how the upload function was not workig