Rik,
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It sounds like your problem is a little deeper inside the instrument? But if it ever turn out to be the step attenuator (HP part # 33321-60036) this experience might offer some past dealings with the 8594E.
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A unit I initially obtained had problems with intermittent levels when switching gains.? It turned out that the tiny rubber O-rings on the ends of the step attenuator solenoid plungers had deteriorated over time and several simply fell off.? This resulted in the leaf contacts not securely touching the plated contacts on the glass substrate.
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I started to seek replacement O-rings but then found out that selection of the material was somewhat critical to prevent out gassing of the synthetic rubber from compromising the conductivity of the substrate contacts.? This then led me to search for an agency who could repair the attenuator.
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I eventually found a concern who specialized in repair of these attenuators ¨C Test Equipment Plus located in Arizona ().? But if you use them their prices are rather beefy for repair - $400 for this particular one.? But if this is (or will be) one of your mainline analyzers I highly suggest using them.? When the attenuator was returned it was accompanied with network analyzer plots showing the performance of the repaired item.
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If you so choose to attack an attenuator problem yourself I will caution you to be extremely careful when disassembling these items.? Yes, simply getting them out of the spectrum analyzer is a little labor intensive but taking apart the attenuator can easily lead to possible damage.? I have the experience to do so but obviously defer repair to a fully capable company.
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As for your problem since it has more or less determined that the attenuator has not sustained damage there may have been possible damage to the first converter from the input being overloaded with the attenuator in the 0 dB state (direct pass-thru).? Looking at the CLIP it appears that the levels found at each input stage are:
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CAL input signal: -20 dBm @ 300 MHz
Attenuator setting: 10 dBm attenuation
Attenuator output (A4 first converter input): -30 dBm (obviously)
A4 first converter output (A5 second converter input): ~-41 dBm +/- 2 dB @2.1214 GHz
A5 second converter output (A9 third converter input): -44 dBm +/- 2 dB @ 321.4 MHz
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All levels are referred to 50 ohms impedance.
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Hope this helps.
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Greg
