Agilent PSA E4440A spectrum analyzer: LO1 unlock  - Page 1
Forum section: electronics / repair

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 22, 2024, 04:39:19 pm
content: Hello,I am trining to fix a Agilent E4440A 26.5 GHz spectrum analyzer. I will post here the repair avancement.Any help will be appreciated on this repair. Thank youFirst inspection:The SA boot but I have two type of error :- "1st LO unlock"- "1st LO unlock, Failure to acquiring single loop FracN LO loop"If I lower the SPAN down 2 MHz, the SA stop sweeping. For a SPAN value > to 2 MHz it start to sweep again.To investigate I have a generator up to 3GHz another SA (not the same) and a scope.The schematic and service manual can be find here :https://www.testworld.com/wp-content/uploads/service-guide-keysight-agilent-e4440a-e4443a-e4445a-e4446a-e4447a-e4448a-spectrum-analyzers.pdfhttps://www.keysight.com/us/en/assets/9018-04012/service-manuals/9018-04012.pdf?success=true

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 22, 2024, 04:54:11 pm
content: Here is the E4440 block diagram

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 22, 2024, 08:25:11 pm
content: Just got the result for the A18 YTO output. I insert a coupler to mesure to rf sweep.The spectrum analyzer sweep from 10 MHz to 26 GHz.I was forced to increase the sweep time to be able to mesure it with my spectrum analyzer.Sweep frequency span seems to be OK. Output power is approximately 15 dBm.The YTO seems to be OK.What should I look at next ?

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 22, 2024, 09:24:47 pm
content: Looking at the A21 SLODA unit (LO distribution amplifier)The "first LO out" port seems to be OK. Same response than the YTO and 13 dBm output signal.The "LO band output" seems to be OK. 3.8 to 6 Ghz frequency response with 14 dBm output power (don't know why it doesn't go up to 7GHz for the Lo band)The "HI band output" seems to be OK. 3.2 to 6 Ghz frequency response with 14 dBm output power (don't know why it doesn't go up to 7GHz for the HI band)Need to look at the "Sampler output", I will do it later.

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 22, 2024, 10:21:21 pm
content: Now I will look at the A20 low band unitI applied a 800 MHz (-18 dBm) signal at the input of the spectrum analyzerLooking at J1, input port of the A20 board, signal is here at -40 dBm. That seems OKLooking at J7, output of the A20 board, the signal is strange. I should normally get a 321.4 MHz IF signal at -43 dBm. What do you think ?

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 08:33:29 am
content: Hello,Does the J7 output signal seems OK for you ?I think it is OK for a spectrum analyser FI output.

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 09:02:59 am
content: Another point:- When the Span is set with a value superior of 2 MHz, (2.1 MHz in this mesure) the unit is sweeping. On the A21 LO output. The LO is sweeping on a 60 MHz bandwidth.- When the Span is set with a value inferior of 2 MHz, the unit is not sweeping and I have got the error "system error, Pretune DAC calibration Fail"With the Span set to SPAN ZERO, the LO is completely unlocked :With the Span set to 1KHz, the LO is first unlock but converge after a time to a lock :

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 10:18:13 am
content: From what I see and understand :A18 YTO oscilator, A21 LO distribution oscilator and A20 Lowband board seems to be OK.Problem seems to be more on A13 Front end driver board or A12 LO Synthesizer board.Can you help me on this repair ?From what i read in the service manual the error message I have ("1St LO unlock, failure acquiring FracN frequency lock") refer more to the A12 board.Here is what I plan to do:1-Verify the sampler out signal, should be 0dBm at 4Ghz at the power on of the unit.2-Verify the 600 MHz signal from the motherboard. It should be at about -5 dBm3-Verify the 10MHz signal , it should be at 2 dBm

author: iAleks
author_rank: Regular Contributor
timestamp: December 23, 2024, 12:00:55 pm
content: Hi! I have this error 1st LO unlock on my Agilent E4440A, and repair it, but it was a long time ago, I don’t remember all the details, when I get home maybe there’s some information or photos left. I remember i found not working amplifier (MGA-86576) on board but im not remember what board name, maybe A12.. I think this amplifier was right after some SMA connectors.On youtube you can watch channel "Signal path" he repair similar errors, and explained the diagnostics in great detail.Maybe this amplifier placed after this SMA

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 12:27:26 pm
content: Hi iAleks,Thank you for your help, it is appreciated ! I fell lost on this repair.From my measurement the problem is from the A12 board but I do not have the E4440-60049 Extender Board to investigate more.How did you proceed to find the non working amplifier on A12 ?I have not see any similar problem on the Signal path channel for the E4440. One repair is on the LO2 filter part and the second is on the pre amplifier optional module.Can you find back how you solve this OL1 unlock on your unit ? It will help me a lot.

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 12:44:10 pm
content: iAleks,Here is the A12 board. Does it look familiar to you ?A12 is a module with two pcb, I do not see a MGA amplifier on the TOP. Was it at the bottom ?

author: iAleks
author_rank: Regular Contributor
timestamp: December 23, 2024, 01:04:17 pm
content: I dont have extender board toi think im solder some flexible rf cable> then turn on analyser> then do measurements> then turn off analyser> then resolder on other place> turn on> do measure like this, "signal path" do like this method on some video.About signal patch he repair similar model from agilent or HP with similar block diagram, in this moment i cant find it (I'm at work now, cant watch youtube here)In my memory that unit with that amplifier looked like this photo but i'm not sure, i need to go home and try to restore my memory.

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 01:29:24 pm
content: Great ! Let me know if you can find back something on your E4440A or if it was a repair for a different Agilent unit.I am clearly stuck at the moment.

author: matthieu.e
author_rank: Regular Contributor
timestamp: December 23, 2024, 07:37:39 pm
content: iAleks,Thank you for all the details. I will check this gain block and let you know the result.