HP 8568A Spectrum Analyzer display fault.

[Simon Spiers]

Hi all, wonder if you can help>
I have just moved my 8568a  from one side of the workshop to the other and now it has a problem.
When the unit has been on for a while the CRT starts to show scrambled characters and the graticule seems to vanish.
I have been over both units cleaning edge connectors and checking ESR of the tant caps but still no joy,
It also shows the check instrument 1 led one this fault starts. Which is instrument 1?
The actual waveform displayed looks un corrupted, so I am guessing the fault must lie in the display units character generation section?
Any ideas please.
Simon

[rob.manderson]

Hi Simon
  the instrument check leds don't directly correspond to display/rf unit in the way you're asking.  I just checked in my manual and Instrument 1 corresponds to a digital display failure.  Their instructions are to check the bus interconnect cable (the 50 pin one).  I had a connector failure on mine - I found that using a very fine pair of tweezers to push the edge connectors out slightly resolved a lot of intermittents.  (I'm referring to the end that plugs into the RF section (bottom section)).  If you remove that end of the cable you should see what I mean.  In the end I bought a 50 conductor DB50 printer cable and a replacement Amphenol connector and rebuilt the cable from scratch.

Even though you have an 8568A I highly recommend the Artek manual set (US$20) for the five manual set.  I'd ask if they have the 8568A RF section.  The only difference is that the 8568A has the older HP proprietary processor whereas the 8568B has a Motorola 68000 processor (and of course all the changes that entails) but it's all confined to the processor section - all the interesting bits, RF, are the same.