Does hp 8568 spectrum analyzer unit work with other hp display units

[jyrgen]

Hi, I'm looking into buying a spectrum analyzer and see that the cheapest option at the moment would be to buy the hp spectrum analyzer and display unit separately. If I buy the 8568 spectrum analyzer unit, could I then buy for example a 8566 display unit? 

[Mr Simpleton]

TTBOMK Display unit 85662A is used both in the 8566 and 8568.

Make sure you do have proper working cables between the two boxes. These are turning into hens teeth... and will set you back plenty of $$$

[G0HZU]

I have both 8566 and 8568 models here and although I've never actually tried swapping the display units between them I think they are compatible.

However, I agree with M.S. that you may have issues obtaining the necessary cables.

Also this approach is highly likely to prove to be a false economy because the market will be awash with split units. i.e. usually either the RF unit or the display fails and the owner then splits the unit and sells the good half at a premium price. But some will then also sell the bad half as 'untested'   and they will also sell the cables separately. This will bring in more money then just selling the complete unit as faulty.

So my advice would be to pay the extra for a complete working analyser (RF unit + display unit + cables). But you still need to allow for the risk that the analyser will have niggles or faults because few people will be able to fully test/prove these analysers.

I bought my 8566 as an ex rental unit and I got it cheap as a direct purchase from the rental company when they retired it. Whilst it is a bit scruffy with a few battle scars it should at least have been maintained and calibrated by the (top UK) rental company I got it from.

It's proved reasonably reliable in the 4 or so years I've had it but I've had to replace a few caps in the RF unit and I also had to spend some time inside the display unit getting the best from the CRT. It now has a really crisp display and I didn't have to use any scary cathode zapping methods to get this performance from it. I just studied the circuits that drove the CRT and fixed and adjusted it all for best performance.

But there are plenty of display units out there that will have very tired CRTs or other issues. Also plenty of RF units with overloaded/blown up RF front ends requiring a new mixer or attenuator assy.

[MarkPalmer]

Try to avoid buying the RF deck and display sections separately if at all possible, and buy a working pair with the cable set.  This will often save you a lot of hassles in getting a used analyzer up and running.  If no other choice is available, 85662A displays will swap between analyzers with one exception, and you have to watch closely for it with display sections for sale.  There are 85662A's with option 67, it is only labeled on the back serial number tag as an option under the serial number. This display is made for the 8567A RF deck and if it is used with the 8566 or 8568 analyzers it will operate, but there will be some functionality limitations on the 66/68 RF decks that require some internal modifications to the display to get full functionality.  The 8567A was an economized version of this analyzer series and the last one of the 856X series to be developed.   

-Mark-

   

[PaulAm]

If you buy the pieces separately, you can probably get them much cheaper, but it is a gamble.

I did that, but I like fixing test equipment.  I came out relatively well, I got a good working display unit and an OK RF section that needed the bulb replaced in the main control.  I still have a problem with no response below a certain frequency; I need to get some extenders to track that one down.

You can make the cables, but it is not fun.  The bus cable is a 50 conductor with a centronics connector on one side and a db50 on the other.  It is not wired 1:1, but the connection chart is buried in the service documentation.  You can put a db50 on a 50 conductor SCSI cable for that.

The other cable uses 4 coax connectors in a DB shell.  Those are easy to make up, but the parts are expensive.  Unless you can find a good surplus source, the connectors alone can run over $80 US.

So yeah, if you can find a complete working unit with cables for a price you're willing to pay, that's the way to go.

[jyrgen]

Thanks for your help! I will probably save some more money and buy a working unit then.