Hi Massimo;
i found another thread from Caesar and made him following mail: (I hope he will respond).
Hello Caesar.
I have serious problems with my dearest HP8711a analyzer; already tried a lot, but the problem now is missing schematics around the power supply unit. See threat:
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Problem is that the analyzer sometimes will boot as nothing seems to be wrong, but suddenly shuts down, or mostly the analyzer will not boot at all; the SPMS unit red light blinking; sort of current_limiting hick-up mode. Most discussions with Massimo are indicating defective capacitors anywhere in the analyzer; I already had a defective CAP on the CPU board some years ago; and replacing this one (+5V) was very effective. While inspecting the electrolithic caps in the SMPS I noticed a lot of them leaking electrolithic. So I exchanged ALL 22 caps within the SMPS with high temp, long life and higher voltage rated caps.......no effect. So I Changed ALL CAPS and tantalium ones (more than 20 pieces) on the CPU board..............no effect.........
Currently I am running tests with only the SMPS and the CPU board running; also the monitor supply cable from the CPU board towards the monitor unit is not connected. Still the analyzer will not boot and stays in this hickup mode; FAN silent and no power_up; CPU board status LED only indicating blinking number 8 (only initial power, no software boot possible.) Sometimes at power-on there is a boot as-normal.....strange... I also have the idea that it takes the SMPS an enormous time to recover from an error....when i try it an hour later, mostly there is a boot possible.......Logically I cannot explain this...current limit or no current limit....but no reset time normally with this sort of SMPS units.
I would like to know which one of the voltages is causing the problem:
+5, +12, +15 or -15 Volts... Therefore I need the schematics of the SMPS. As I understood you are the proud owner of a schematic set.... Would you be so kind to make me a copy with a scanner of the SMPS schematic set? I am using this analyzer at home in my "lab" here in Borne in the Netherlands, together with a HP8594E and a HP8559A spectrum analyzers an I cannot live without a working 8711...........
Thanks in advance; Ivo Maatman.