Agilent 8594E – Newly aquired, first questions . . . - Page 1
Forum section: electronics / repair

author: K7SJB
author_rank: Newbie
timestamp: January 25, 2021, 01:29:40 pm
content: Agilent 8594E – Newly aquired, first questions . . .Greetings all, I spotted a reasonably priced Agilent (not HP) 8594E Spectrum Analyzer on eBay. In viewing the listing pictures, what lit my fire was seeing an N-connector for the tracking generator option. Sweet! So, I did what any irresponsible collector of test equipment would do, I put in an offer. And much to my surprise, it was accepted!Long and short is, it was missing the display module. And, of course, while searching for a used or repairable display, again on eBay, I found slim pickin’s. I did see the flat-panel upgrade being offered, but it seemed to be excessively priced. And, the reviews did not strike me as stellar. I also knew that I had a small (12”) black-and-white NTSC surveillance monitor packed away somwhere. . . But within a few days, I spotted another HP (not Agilent) 8594E in as-is condition with an error messages on the screen. I did some research and came to believe that a likely cause of those errors was simply a dead battery! Anyway, the unit in question had been rack mounted and at first glance looking a bit ragged. I downloaded the listing pictures so I could view them with full pan-and-zoom on my more familiar Windows image-viewing software. And convinced myself that far from ragged, the unit seemed exceptionally clean! I jump in it. Again, placing a “Best Offer”. And, like before, I got it!Did I mention that the first unit was also sold as-is? The listing claimed: “powers on, fan and pilot light working – but display dead”. No lie! It’s kind of hard to see images on a screen if that screen is infact; unpowered, defective, run over by a bulldozer and sitting hundreds of miles away in a landfill. (Okay, so I’m speculating a little here.) 😊 Because of the darkened-glass-window and RF-shielding mesh, seeing that the display was missing required opening the case. Other than the missing display, I was quite happy with the unit. And I was thrilled to see nothing else appeared to have been disturbed. Even that sweet little tracking generator was seen nestled into its happy little home – and all appeared to be pristine. Being that the unit was sold as-is made me feel especially lucky that only the display was missing.So, I have some questions:1) What can I do with the parallel port? Can I find software to work with it? Especially, to save and restore “Correction Constants”?2) Same question as above; But, substitute GPIB for “Parallel Port”. Is anyone knowledgeable about using the free version of LabView with these analyzers?3) I fear my analyzers may both have lost Correction Constants. Can I reasonably expect to have a useful instrument by simply loading in the default values? (Calibration may have to wait.)4) Generally speaking, how far off of “flat” can one expect an uncalibrated (default) unit to be? And can I expect an uncalibrated unit to pass the startup assurance test?5) Does failing the startup assurance test prevent the unit from working?6) Should I be looking for memory cards? Or, are they useful?7) Of what use is the rear-panel “AUX” connector?8) Assuming I trust the leveled-output on my HP 8657D RF generator (up to 1,030 GHz), can I use it to “fake” calibration and then extrapolate my way up to 2.9 GHz? In other words, can I expect a certain amount of linearity with the Correction Constants?9) Can the membrane buttons be cleaned?10) * Possibly, more questions later. * 😊Now, all that aside, I did spend my time waiting for my units to arrive doing my homework. I downloaded manuals and pictures, and read up on maintenance issues. I even found this EE blog forum! I watched a ton of YouTube videos, and I copies out and photoshopped a few block-diagrams and other tidbits. I will upload a few to share now. I also created a few text files bringing together some useful (and/or uncluttered) information. Oh, and I mistakenly out-took one block-diagram not useful to me. But, as long as I have it, I will upload it too (Agilent 8590 Block Diagram).Enjoy,Stan

author: K7SJB
author_rank: Newbie
timestamp: January 25, 2021, 01:34:09 pm
content: (More Attachments)

author: KB7ZUT
author_rank: Newbie
timestamp: February 22, 2021, 03:10:22 am
content: Hi Stan,Congrats on the new acquisition!I just stumbled into your post here looking for info on GPIB interfaces for my newly acquired HP8591E. I found my SA on Craig's List while searching for the end of the internet one evening. Initially was looking at Ebay, but on a recommendation from an YouTuber, I decided to go looking on Craig’s List to see what was out there. Bingo! I found a "low mileage" hp8591e with the tracking generator (option 10) and the high accuracy oven controlled xtal + the 30Hz BW (option 140, which is options 4 and 130 combined). I offered the seller full asking + shipping before I got finished reading the description.The seller had it in storage and had not used it in over 6 years, so I was really buying without having a clue if it was still fully working. At the price being asked, I was willing to roll the dice "sight unseen" and pull the trigger. I lucked out, and the 8591E was fully functional and the Lithium memory backup battery, installed in 1993, was still alive with all of the flatness data and step attenuator data safe and sound. I spent the first 30min after unpacking it and plugging it in just copying the calibration data into a notebook per the service manual procedure. I know the data can be recreated, but some of the required equipment I don’t have access to.On my 8591E, the flatness data is rather mundane (<1dB +/-) until above 1.5GHz. Then the offset are as high as 3db+/-. Using a trusted signal gen you might be able to back into the required flatness data. That said, I have not tried to do it myself. If I understand correctly, the tracking gen is calibrated using the SA, so you end up having more error if the SA is not correctly offset.I have a replacement 3.6V AA lithium battery on order from Mouser, but it is stuck in Texas after the huge winter storm hit last week. I did check and the original battery is holding on at 3.7 volts. Truly amazing after 28 years.As I'm relatively new to this instrument, I'm not going to be much help on your other questions, but I will stay tuned to this thread to see what you find out.73,-AndyKB7ZUT