ok so after some research and some more testing I can confirm its a bad Yig.
I removed the YIG and ran it externally with three PSU's, two for voltage and one for a current limited source to control the main coil (didn't bother with the FM coil) .
This proved to me that the YIG has two problems, it wont cover the required operational frequency span (it has gaps) and then it shuts down after 5 minutes of operation from cold.
So a new YIG is needed.
This seems to be the most common fail on these SA's, 2nd hand Yig's can be got from the far east but you takes your chances there!!!
A company is CA can provide recondition units with a guarantee, provided you donate the faulty Yig.
But it's a tough call to know if the Analyzer is worth the 1000 Euros (approx) it would cost for a Yig.