[Test-Equipment] HP 8640A

[Marv E Ads]

On Tue, 05 Feb 2002 09:23:44 -0700 gil smith <gil@vauxelectronics.com>
writes:

Hi Gil,

> Hi folks:
> 
> I just got an HP 8640A generator, and it seems to work pretty well, but
a
> couple of things need attention.  
> 
> 1) There are a couple of spots on the Range switch where the output
drops
> 10 or so dB until I wiggle the knob a bit -- can this switch be
cleaned,
> and if so how?
> 
> 2) The output is quite flat on the low ranges (though my 8601A covers
that
> nicely already, so I'm mostly concerned with 100-500MHz on the 8640). 
But
> on a couple of the upper ranges, the output level varies by almost 10
dB as
> I crank the freq through the range.  Is this just an alignment issue,
or is
> something else perhaps wrong?

  There is nothing to align.

   You might check the mechanical coupling on the range switch shaft to
see if it has slipped.  I think the forward part selects the range and
the rear section selects the appropriate low pass filter.  If those are
out of sync it might cause something like what you're seeing.

   Easy to see with the bottom cover off.

>  On the SA, the harmonics look reasonably
> low, so I'm hoping it's an adjustment and not something damaged.
> 
> 3) What is the external doubler that is used for the upper range?

  It is a simple diode doubler -- operates at a fixed level. 
Mini-circuits sells a functional equivalent with BNC connectors for about
$30, if I recall correctly.

> 
> 4) What is different in the 8640B, besides the counter and the optional
> internal doubler?

  The synchronizer, so that the thingy doesn't drift!  :-)

> thanks in advance,
> 
> gil smith
> 

Good evening,
   Marv  WC6W  


P.S. -- I found a pair of the male connectors for the HP-141 service
cables but, not the females... they seem to have wandered off.












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