| Products > Test Equipment |
| HP8595E spectrum Analyzer: readings at -40dB and CAL SIGNAL NOT FOUND |
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| MarkL:
One other thing that might be worthwhile is to look at your calibration constants (CAL --> Service Diag --> DISPLAY CAL DATA) to see if anything is way off. Typical values are described on page 584, and/or share here. The cal data and correction constants are stored in NVRAM, and the only reason I bring this up is the unexplained weird (corrupted?) date. If CORRECT OFF gives you pretty much the same results as before, meaning approx 40dB down when the 40dB attenuator step is supposed to be out, I would say it's time to isolate the attenuator and take a closer look at what it's doing. The other dB differences you're seeing are relatively much smaller in magnitude, and I wouldn't worry about them yet. Successful self-calibration might take care of them. Since you have a signal source and another SA, I would connect the source to the 8595E input (say 300MHz @ 0dBm), and the other SA to watch the signal coming out of the 8595E attenuator. The attenuator output is the SMA connector on the top (on the end with the ribbon cable). You can then exercise the attenuator like you did before and watch the changes in output amplitude. If you get bad behavior with the 40dB step, I wouldn't jump to disassemble the attenuator just yet. I would confirm that the 40dB step control input is working. There is a section in the Assembly Repair Guide on what to expect from the control signals on page 291 and table 6-11. |
| MarkL:
And also, if you haven't done it already, backup your correction constants using the procedure described in Chapter 3 in the Assembly Repair Guide. If something goes wrong and you lose the NVRAM, or your battery dies unexpectedly, you'll be much happier. |
| auato:
I'm having trouble extracting the assembly to which the attenuator is attached. In meantime I share with you that CAL --> CORRECT OFF does not produce any change and and calibration constants appear as below. I'll update you when I get the attenuator out the assembly... now I have a coaxial that is pulled like a string and I don't understand where it is hooked up and what else I have to dismantle |
| DavidAlfa:
You can easily check the attenuator without fully disassemblying it, only remove the coax connections and measure resistance with the DMM between input and output. Adjust the attenuation level with the knob, from 0dB all the way to -75 or the max. it allows, if it measures open circuit at some point it's very likely you have a bad element. That's how I got the definitive hint before opening it, the module either bypasses (shorts) or leaves the elements in series, there's no way to create an open circuit except by broken elements. |
| rf-loop:
--- Quote from: auato on December 12, 2023, 09:24:47 am ---I'm having trouble extracting the assembly to which the attenuator is attached. In meantime I share with you that CAL --> CORRECT OFF does not produce any change and and calibration constants appear as below. I'll update you when I get the attenuator out the assembly... now I have a coaxial that is pulled like a string and I don't understand where it is hooked up and what else I have to dismantle --- End quote --- Are you serious you do not have service manual. There is all explained including disassembly and assembly procedures. For take attenuator out... you need take rf frontend out first and after then all is more easy. It is very easy when do it just right way. And note that some filters and some other components are mechanically fragile even when they do not looks like fragile and then also care ESD and repeating again: ESD! Also I recommend keep your tools and fingers out from YTO YIG tuned oscillator except is absolutely necessary. And then... never enter any DC after attenuator... (or DC to RF input when DC bloc is turned off...) You can find a lot of instructions here as well, if you look carefully at what is there to apply. https://xdevs.com/doc/HP_Agilent_Keysight/08590-90316.pdf Also due to its age it is wise to check and replace battery. (and even when service manual do not ask to use support battery.. I have always done it with support battery (but it need also take care how to use it) for keep Mr Murphy outside from my work bench) There is also somewhere available full CLIP for these (I have only original paper versions, whole repair service set, long time ago purchased from HP/Agilent) |
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