AnsweredAssumed Answered

HP8591A problems

Question asked by bob47 on Jan 6, 2010
Latest reply on May 19, 2010 by MikeM
Hello All.
I have "2" HP8591a's which seem to have various faults of which I am unable to diagnose and repair.

The first unit has a tg unlev displayed on the screen. Freq and ampl cal have been performed and then tg cal.
Everything seems to cal sucessfully but tg unlev seems to always be displayed when using the tracking generator.
When the src power level is adjusted it seems the trace jumps 10db steps instead of the smoother 1db.
The original fault was that when the src level was adjusted above -6db the tg unlev message would come up.
By calibrating the tg has made the unit worse. I am unable to get it back to where it was.

The second unit is worse. It has the freq uncal on screen all the time and changing various spans can make it go away.
I have tried the freq cal method but it reports no cal signal found. I have verified the cal signal is there and the amplitude is correct
with another analyzer.
If I set the centre frequncy to 300mhz and span to say 100khz the cal signal is displayed.
According to the manual if the freq uncal is displayed the yto is out more than 20mhz.
Other strange things must be occuring in software.
If I display options it reports option 001 and 011 of which 010 is installed.
No 75 ohm options are fitted.
The serial number is corrupt.
The clock shows funny characters and the year 2066
When preset is pressed the ref level displays 23.69db

The default cal data is present so sometime earlier it has been reset.
I reset the ram again but It is still unable to be cal'd.

Can anyone advise where the default cal data, options etc are stored?
It seems the default cal data is corrupt. My understanding from the manual is
there is default software to get the unit going and then the cal data is stored
in ram when a cal has been performed.

Regards Bob.