On Sun, 10 Jun 2007 12:03:04 -0400, "Leland C. Scott"
wrote:

+++James;
+++
+++One of the problems buying used test equipment is the manufacture finds
+++there is some weakness in the design resulting in frequent failures, one
+++reason why they may quit manufacturing it.
+++
+++I don't know if the HP signal generator you mentioned is one such item. I
+++remember in some back issues of QEX somebody came up with a modification to
+++replace a section in the output of a HP signal generator that was known to
+++be particularly failure prone, the original part used isn't available
+++anymore if I remember right.
******************

The HP generator I have is a standard that HP sold for commercial and
industrial use throughout much of the 1990's but now is discontinued.
The one I have is a HP8656A with the attenuator replaced with the
same one that was used in the HP8656B. One of the HP8656A's main
weakness was that of the attentuator at the output. The genreator has
an input for connection to a high stability time base which improves
the performance especially when using it at frequencies around 800
MHz. I also have a 10MHz. high stability TXCO that keeps the accuracy
of the generator frequency set to less than +/- 1 Hz.

Obsolescence is not necessarily due to problem plagued unit though
that can be a cause. WIth HP8656/57 series that may not have been the
problem. Lower demand and cost of manufacturing can also lead to
obsolescence. Lack of demand can be due to not having features and
options that the end user demands. Often a new model is introduced
with more bells and whistles as well as defect fixes that will all but
obsolete the previous model.

I have been very happy with the unit I have. The front keypad is still
in very excellent shape as the unit I have was on the factory floor
and control of it was via the GPIB connection from an HP workstation.

james