Hi,
Thank you rastro for your advice.
The SHF-0189 I have ordered (to Utsource, good service, two week delivery from China to France) have arrived. I had ordered 3, just in case (which has proved to be a good decision)...
I managed to remove the defective chip with my dremel, did not succeed to completely desolder the ground pin, but I removed enough metal to be able to solder the new chip. I had to remove the shield above the IC, to gain access to the pins.
The first soldering attempt failed, I broke the case while trying to bend a pin.
I did a much better job on the second try, see photo.
It is not perfect, but it is not easy because of the very small size of the IC (~4mm width) and the adjacent components are very close.
I did not bother to rebuild the shielding.
And voilĂ : No more errors, self calibration passes, output signal is in spec.
Just the backlight intensity is a bit low, due to the high hour count. I can live with that, but if anybody has an idea ?
While the beast is open, I have moved the back connectors to the front: quite easy, all the cables, even the semi-rigid one can go back or front.
In the meantime, I have upgraded the firmware to the latest available version 5.93HX on R&S website (lost the self calibration tables in the operation, but not a problem now that everything works, it is rebuild in a few seconds)
You know what? ...
Michel.