HP8594E 3GHz Spectrum Analyser fault diagnosis, detailed testing & analysis & diagnosis of fault.

Here we look at a Hp Agilent spectrum analyser 9khz to 3GHz model with a reported foul of not able to calibrate & RF level reading low. We embark on a path of verification, & a series of tests of internal circuits & modules inc the calibrator & 600MHz oscillator & reference oscillator, PLL circuits & 3rd converter analysis finally we diagnose the fault. During this process we use numerous test instruments to measure signals & help diagnose the fault.

[@M0XFXUK]

I really enjoyed the video, I think the problem is on the A25 counter board as a cap may of leaked and taken out an 8 pin PLL IC, it's just a guess but I seem to remember fixing the same problem some years ago. It's a shame that Keysight / Agilent / HP will not release the component level schematics and service information on which is now quite old equipment. Keep up the good work

[@alandrury9955]

Thanks for a great video. I really thought you were going to get it, shame it wasn't to be. I too was given an 'almost working' spectrum analyser which I'm still trying to fix!

[@jr_electronics]

Great video. Is the 10MHz jumper to REF IN on the back of this unit? Can it be bridged with just an simple BNC to BNC cable? That is the main cause of the "REF UNLOCK" seen on the display... no 10MHz signal. In the service manual, page 649, states: Troubleshooting Hints Refer to Foldout 11-2, 11-3, or 11-4, RF Section Overall Block Diagram for your analyzer, for more information. 1. Check the rear-panel cable connections for the 10 MHz reference. When using either the standard 10 MHz timebase or the precision frequency reference, make sure that the 10 MHz REF OUT on the rear panel is connected to the EXT REF IN. The W6 jumper is supplied with the analyzer for this purpose. When using an external 10 MHz reference, make sure it is connected to the EXT REF IN on the rear panel. Are you sure there was a 10MHz signal fed to EXT REF IN?

[@microwave-vh2uc]

I was thinking the same thing during the whole video

[@microwave-vh2uc]

and then he went back to the analyser and connected the ref out to the ref in and wow it works now.. Then a few hours of reversing all the previous unalignment procedures and everything works as it should.

[@dragonlard4595]

Thats very valuable Information, youre providing there. Keep up with it. :)

[@b16a2Johnk]

I’m no expert but I suspect your A25 Counter lock bord is not getting 10MHz reference The message on the display REF Unlock is telling you the pass through BNC on the back of the unit is missing failing to pass the INT 10MHz back into the machine Please try looping the 10 MHz reference back to the analyser then continue your diagnostics The missing pass through is shown on the block diagram however not present on your analyser

[@Aligreta]

I think thats key first to verify before further trying steer oscillator that is just free running

[@gizzzmonic]

does RFMan stand for "read factory manual?

[@ptronix]

The clue was on the screen, ref unlock. No connection on the back of the unit , on mine I had a big metal bnc to bnc Bridge. Use a siglent these days, much better unit, but of course its much more modern

[@rfmanrfman4536]

Negitive my friend, it was nothing to do with the rear connections at all, also the message on the screen was present when in the cal adjustment mode, this clears when the cal adjustment secret code is exited, if you watch the video carefully you will see mid way that internal signals in the 3rd converter are incorrect due to the PLL unlock condition, the int ref oscillator is running fine, & as you can see in the video the 10MHz ref oscillator signal is getting to the 3rd converter. Nothing to do with rear connections in this case.

[@jr_electronics]

@@rfmanrfman4536 A great video, just wondering, as you have not said, was the rear jumper on? I have just acquired my first SA, and this is the one, and it does not have the jumper. Wondering if I can just use a short BNC to BNC 50 ohm cable to bridge the 10MHz output to the ref in on my unit?

[@bb-andersenaccount9216]

great, great content

[@Aligreta]

While ref unlock is present, that vco is free running and wont be spot...

[@michsmi8297]

I have a similar model to this with a faulty power supply. Do you have your own contact details in case someone wants to send a repair for you to look at? I should like to send my spectrum analyser in!

[@dayleedwards3521]

In random twiddling the monitor, you have buggered the geometry. Open your eyes and look, the words are small at the top, big at the bottom. READ the bloody manual first. This is not the way to tackle any repair.

[@rfmanrfman4536]

I did chuckle when i read this, Dave strewth mate i did read the manual, you sotherners down under telling us lot 🤗from the old country how to go on well i never.

[@Samucas81]

Hello, if anyone can help, I need the firmware for the HP 8594A, thank you.

[@johndavis1465]

Dumb measurement for cal port using Power meter because waveform is squarewave thus has harmonics.

[@Dickwooten]

I'm glad I read your comment. I could have made the same mistake if I had a power meter (which has always been low on the list for my bucks)-even though I should know better. I just use another spectrum analyzer when I look at it, so I haven't had that issue.

[@sathishnadar5433]

softEX softs like a mouthorgan.. why?