HP 8592B spectrum analyzer

[taydin]

Finally got a chance to look at this again. After giving the power supply an ultrasonic bath, the power supply is still behaving the same way. All outputs measure normal when not loaded, but the PSU cuts out when any output is loaded. So it seems I need to build an equivalent PSU for this SA.

I have done the cal tests and both frequency and level CAL's are failing with SRQ 110.

I have checked the output of the YIG using my scope, while the SA was scanning the entire span. The YIG output always stays very close to zero So I guess I will either need a new YIG, or build an equivalent circuit in there (perhaps some kind of high precision VCO).

I have seen YIG's for this SA for sale on ebay, but those are not new and are probably salvaged from other old SA's. Chances are they don't work, either.

[taydin]

Spent some time reading the "performance verification manual" of this SA. And good thing I did! Realized that I have measured the YIG output not correctly. The RF front end of this device is quite involved. It has two LO's, and two mixers. One is for the low band (0 - 6 GHz), and the other is for the high band ( 6 - 22 GHz). For the low band, the YIG oscillator is used for LO generation. For the high band, a YIG filter is used to isolate the third harmonic of the YIG oscillator output.

Based on this new information, I have reassembled the RF front end and measured the YIG output at the CORRECT SMA port, and I have seen 2.85 GHz output using my scope. The amplitude, as measured by my 1 GHz BW scope was -0.5 dBm, so probably closer to +10 dBm in reality, which makes sense for YIG oscillator. So that was a big relief

[taydin]

A few pics of the RF front end assembly:





The YIG oscillator and YIG filter

[taydin]

After putting the YIG oscillator and filter back in, I started to see of the step attenuator at the input is working properly. Removed the rigid SMA cables from the input and output of the 0 - 70 dB attenuator, and connected my signal generator to the input and the scope to the output.

The attenuator's control port was still attached to the SA, so I was able to change the attenuation using the SA's control menus. Applied 20 MHz, 0 dBm test signal to the input, and at 10 dB attenuation was expecting to see - 10 dBm at the output, but saw much, much less than that. In the end, it came out that one of the 20 dB segments in the attenuator is stuck, so the attenuator seems to be adding +20 dB more to whatever is programmed.

I adjusted the reference level setting in the SA to compensate for the step attentuator extra attenuation, and i was able to see a peak for the first time! The peak level was completely off, and the frequency indicated by "peak search" was was by 2 MHz from 20 MHz, but I'll worry about that later. For now, my focus is to get the step attenuator to work. One step at a time 

[taydin]

This is actually good news! Step attenuators are much cheaper than YIG's. But I don't know if these are available on ebay, need to check. But I've also seen videos where people attempt to repair these.

[taydin]

There were two observation that initially seemed strange to me. Below is how the spectrum looks like when it's doing a sweep of the entire 22 GHz span and nothing is connected to its input.

1) The spectrum is drawn outside of the grid. I think this is because of the step attenuator working incorrectly, and once that is fixed, I think the graph will move into the grid.

2) The spectrum has an unexpected step at about 6 GHz. I interpreted this as a possible damage in the mixer, but now I'm thinking isn't probably the case. The RF front end has two separate paths, one low and one high, so I think that step corresponds to the point where the sweep changes from low to high range. But I won't be sure until I feed this a slowly sweeping signal between 0 - 15 GHz.

[LatethanNever]

Hi, Sorry if I am hijacking this thread.

I recently acquired an HP 8592B spectrum analyzer and it is in good working order.   However, it has no options installed but I would like to find a way to connect it to a computer to control it and/or pull data from the unit.  There is no HP-IB interfce (Option 021) and no RS-232 interface (option 023).   There is only a 9-pin "AUX Interface".   I've skimmed through the 8592B Spectrum Analyzer Installation, Verification, and Operation Manual https://literature.cdn.keysight.com/litweb/pdf/5958-7098.pdf and I can't find much information about this connector.   I was hoping it is some sort of serial connector which would give me some control/access.

Does anyone have any experience about this "AUX Interface"?

Thanks