HP8648C Acting Up?

[Electro Fan]

After completely normal operation the 8648C turned on with a display that says "5 second self test" - which would be fine if it didn't say on for about 10 minutes.  After about 10 minutes I heard a relay click and the normal display came up but none of the buttons seemed to cause normal actions.  Power cycling it has put it back into the "5 second self test" mode again.

Below is a snippet from the manual.  It talks about the GPIB but there is nothing attached to that....

Any idea what might be up and how to fix it?  Thx

[Electro Fan]

Update:  I think the 10 minute interval might have been somewhat longer - but when it happened again I hit the local button and the Sig Gen returned itself to normal.  Maybe I got it into the non-local mode and there was no good way to get it out since the GPIB isn't in use?  Anyway, it's back to normal.

My theory is that that it knew I was checking with the guys on EEVblog - and it decided it was about to get fixed one way or another - so it decided to go back into normal operation.  Kind of like when someone calls IT for support and the IT guy shows up and everything is running fine.  These boxes can sense when they are going to get fixed so sometimes they just give up and behave.    It wasn't operator error, honest. 

[tautech]

Update: ........
It wasn't operator error, honest. 

Yeah right.