Re: Defective Power supply in HP8711a Network Analyser.

Hello Massimo.

Going back to basics it proved that the SMPS of the HP8711a hates it
to be plugged into the cabinet, even only connected to the backplane;
result: hickup mode. (so no 8711 units in the 8711 rack at all!!)
In the open the SMPS works fine (all voltages unloaded), but I found
out that the -15 Volt GND return hates it to be connected to GND of
the cabinet (this connection is on the backplane of the 8711) or to
GNDs of the other voltages.
All voltages are fine, no DC shorts between anything, and I can GND
all voltages, except the -15V. By grounding only a few mA will float
though, but this brings the SMPS in the hick-up mode, like it does in
the 8711.

Could no-load situation bring this? Or is something wrong with the
current sense system, so the SMPS does not boot?

Do you have any idea?

Ivo.
.

Relevant Pages

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