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Video Teardown, Analysis and Repair of an Agilent E4407B ESA-E Spectrum Analyzer
Posted by
Hugoneus
on 02 Oct, 2014 18:45
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In this episode Shahriar takes a detailed look at an Agilent (Keysight) E4407B ESA-E Spectrum Analyzer. The instruments reports an “Unlock LO” error message which prevents internal alignments from being performed. Before the repair process can begin, the firmware of the instrument must be updated. The firmware upgrade requires the installation of additional flash memory ICs which is presented in the video. The main processor board with its various components are also described in the video.
The complete block diagram of the spectrum analyzer is presented with a detailed look at the principle of operation of the instrument. All the main functional blocks such as the YIG Oscillator, Phase Detector, LO Path, LO Amplifier, Charge Pump, Pre-tune segments, digital circuits, IF and LO paths are analyzed both in schematic and on the PCB. Several potential faults are investigated and measured.
Watch here: [2 Hours]
http://youtu.be/gb1QMJtwumQMore videos at The Signal Path:
http://www.TheSignalPath.com
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#1 Reply
Posted by
kg4arn
on 02 Oct, 2014 21:01
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Really enjoyed the extra detail and explanation. Thanks
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#2 Reply
Posted by
Hugoneus
on 02 Oct, 2014 22:27
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Really enjoyed the extra detail and explanation. Thanks
Great. Glad to hear it.
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#3 Reply
Posted by
Wytnucls
on 02 Oct, 2014 22:40
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Shahriar, the Steven Spielberg of electronics videos...
Fantastic, keep them coming.
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#4 Reply
Posted by
poida_pie
on 02 Oct, 2014 22:56
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Yet another excellent video. I liked the sigma-delta A-D one as well.
I particularly enjoy the repair type videos you do.
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#5 Reply
Posted by
Hugoneus
on 03 Oct, 2014 03:00
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Shahriar, the Steven Spielberg of electronics videos...
Fantastic, keep them coming.
That is awesome! Thank you.
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#6 Reply
Posted by
vaualbus
on 03 Oct, 2014 05:26
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I really love the video. The schematics seem very hard to understand at first look.i just have a question. This scope go from 9khz up to 2ghz. I see the new agilent/keysight sa (psa and pxa).
For the psa the top model (e4448) go from 3hz up to 50ghz. How it can achive this resolution? What could be different from this sa?
Also I saw on eb a couple options for your sa . For example there is the high stability crystal oscillator for less tha 100 bucks and the fast adc board a cople of houndred of dollars.
By the wave keep on doing this amazing teardown!
Also any idea how the divider can be get wrong?
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#7 Reply
Posted by
miguelvp
on 03 Oct, 2014 06:03
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I did doze off at the beginning because I just ate dinner but then I rewind it and watch the whole thing.
I think your video was plagued with the absence of Daves #666 that's why your divider was dividing by 6 instead of by 4
Awesome repair even if I don't understand why the divider was affecting the voltage reference to jump all over.
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#8 Reply
Posted by
Nermash
on 03 Oct, 2014 06:22
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Watched it all the way through, great content, great presentation
Please keep doing this kind of elaborate videos.
One thing does puzzles me: why the NI input on the U93 opamp was jumping? With stable positive and negative opamp supply, stable reference voltage, I can only guess that inverting input was being slammed beyond the CMIR, but I sure could use 2 minutes explanation why and how the fracN divider wrong division ratio influenced charge pump and voltage integrator:)
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#9 Reply
Posted by
Hugoneus
on 03 Oct, 2014 17:08
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Thank you all.
To answer a few questions,
The Op-Amp which I replaced is a fully bipolar implementation with input protection diodes between the terminals. Saturating the input/output of such an Op-Amp can cause current to flow between the terminals which is what we were seeing.
With the main Divider/4 block non-functional, the phase detector will continuously attempt to push the YIG frequency to extreme ends of its range which causes the Op-Amp (the main integrator) to saturate.
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#10 Reply
Posted by
German_EE
on 03 Oct, 2014 17:34
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Two hours of RF goodness whilst the girlfriend is at the gym. Life is good
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#11 Reply
Posted by
Hugoneus
on 03 Oct, 2014 17:39
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Two hours of RF goodness whilst the girlfriend is at the gym. Life is good
Haha, lucky you. My girlfriend was sitting across the room making faces at me while I recorded.
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I just watched your video completely through and would like to say thank you for these repair videos. They are just perfect and definitely not too long. I have never seen an OpAmp behave like this, so that was something new. And so many other great points you made. Just make more repair videos on Agilent test equipment, I really deeply enjoy them.
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#13 Reply
Posted by
Lukas
on 03 Oct, 2014 20:49
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I watched the video from the beginning to the end, was really informative. Keep it up!
You asked why the LO sweeps at varying speeds, my take on it: (Select text to see it) On the first ramp, it uses the fundamental of the LO, on the second the first harmonic and so on. Since the sweep speed is constant the LO sweep speed has to be halved when using the first harmonic to maintain the sweep speed.
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#14 Reply
Posted by
saraht
on 03 Oct, 2014 22:37
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I watched it last night. I'm not a short-attention-span person, I love longer format videos like yours. I'd hate to miss the detail.
Great work, please keep it up! :-)
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#15 Reply
Posted by
Hugoneus
on 03 Oct, 2014 22:50
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I watched the video from the beginning to the end, was really informative. Keep it up!
You asked why the LO sweeps at varying speeds, my take on it: (Select text to see it) On the first ramp, it uses the fundamental of the LO, on the second the first harmonic and so on. Since the sweep speed is constant the LO sweep speed has to be halved when using the first harmonic to maintain the sweep speed.
Yes, you are right! Thanks for posting the answer!
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#16 Reply
Posted by
G0HZU
on 04 Oct, 2014 00:56
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It's interesting to see inside one of these analysers. We have several of these at work for doing simple system work etc.
I only skimmed the video to look at the schematics and the PCB layout bits but a few things in the video confused me a lot. eg there were several references to an IF at 312.4MHz
I can't see how the IF can be 312.4MHz because most oldschool HP uW analysers have an IF at 321.4MHz. This allows easy generation of the 300MHz LO (from 10MHz) to mix 321.4MHz down to the common 21.4MHz IF.
The 5.5GHz filter looks like a simple LPF using radial stubs and I can't initially see how this can provide a BRF notch at 5.5GHz whilst passing about 3.92GHz with low loss. This is despite the block diagram showing a 5.5GHz BRF symbol. Very confusing. The filter is too simple to allow this (unless some tradeoff against highish insertion loss at 3.92GHz is tolerated?). At a guess those radial stubs will give notches up around 6.5GHz or higher. Normally an analyser will have a steep LPF here in order to provide some isolation between the first two mixers across as much of the LO1 range as possible. My guess is that they have cascaded two LPFs here in order to try and get some steep rolloff to get LO isolation to minimise spurious terms in the two mixers. eg ABS(nLO1 - mLO2) = 321.4MHz. There's lots of smaller radial stubs littered along the IF path and I think these will be there for similar reasons. i.e. to notch out harmonics of the LOs to provide mixer to mixer isolation at many, many GHz. But that is just a guess.
At 1:16:58 the prescaler output is to the left rather than on the right as the bit pointed to by the finger looks like a control line used to select different division ratios in the device?
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#17 Reply
Posted by
apelly
on 04 Oct, 2014 03:11
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Thanks for the video. I could watch quality content like that for hours.
If anything, I thought the end felt a bit rushed. I'm sure you were getting a bit sick of it by then though! I certainly wasn't.
You make great videos, and I appreciate the effort you put in. Thanks again.
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Woot woot. Thanks for doing that.
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#19 Reply
Posted by
Hugoneus
on 05 Oct, 2014 18:26
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Thanks everyone for your contribution.
Don't forget about the Twitter account (@TheSignalPath)!
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Thanks for your videos, I really like the longer videos which go down into the details.
When you show the repaired SA with the PLL module in the last few minutes of the video with the full sweep (before zooming in on the freq of the pll), there is a large signal just at the left side of the display. What is that? Shouldn't the signal level be at the noise floor on the left side?
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#21 Reply
Posted by
Hugoneus
on 05 Oct, 2014 20:10
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Thanks for your videos, I really like the longer videos which go down into the details.
When you show the repaired SA with the PLL module in the last few minutes of the video with the full sweep (before zooming in on the freq of the pll), there is a large signal just at the left side of the display. What is that? Shouldn't the signal level be at the noise floor on the left side?
The PLL is unlocked and the instrument is trying to interpret various IF signals it receives from its several converters. I suspect that some DC offset signal from a mixer is wrongfully interpreted as a tone. Once the PLL is locked, this issue is resolved automatically.
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The PLL is unlocked and the instrument is trying to interpret various IF signals it receives from its several converters. I suspect that some DC offset signal from a mixer is wrongfully interpreted as a tone. Once the PLL is locked, this issue is resolved automatically.
Before I ask my question, I need to say, that I have not done much with RF, but find it fascination.
So, may be the answers are obvious to an RF specialist...
1)
I have an older HP Spectrum Analyzer Model 8596E.
This one also shows a peak at the very beginning of the sweep, when it starts the sweep at 9 kHz.
(Noting connected to the input)
Is it possible that this is inherent to HP spectrum analyzers?
I get a -1dBm at -100Hz
(see pictures)
2)
Why can I set my HP Spectrum Analyzer to start sweeping at a negative value?
i.e. -100 Hz
3)
And one more question, if you know the answer....
Why do most of these spectrum analyzers have a listed start frequency of 9kHz?
Why not 5kHz or 10 kHz or any other value?
Even some HP RF signal generators start at 9 kHz?
Was this an arbitrary selection by HP at the time or is there a significant technology reason behind this number?
Thanks for all your great videos.
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#23 Reply
Posted by
Hugoneus
on 06 Oct, 2014 14:34
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The PLL is unlocked and the instrument is trying to interpret various IF signals it receives from its several converters. I suspect that some DC offset signal from a mixer is wrongfully interpreted as a tone. Once the PLL is locked, this issue is resolved automatically.
Before I ask my question, I need to say, that I have not done much with RF, but find it fascination.
So, may be the answers are obvious to an RF specialist...
1)
I have an older HP Spectrum Analyzer Model 8596E.
This one also shows a peak at the very beginning of the sweep, when it starts the sweep at 9 kHz.
(Noting connected to the input)
Is it possible that this is inherent to HP spectrum analyzers?
I get a -1dBm at -100Hz
(see pictures)
2)
Why can I set my HP Spectrum Analyzer to start sweeping at a negative value?
i.e. -100 Hz
3)
And one more question, if you know the answer....
Why do most of these spectrum analyzers have a listed start frequency of 9kHz?
Why not 5kHz or 10 kHz or any other value?
Even some HP RF signal generators start at 9 kHz?
Was this an arbitrary selection by HP at the time or is there a significant technology reason behind this number?
Thanks for all your great videos.
The signal you see below 9kHz is actually at DC. It is normal that spectrum analyzers show that signal especially the ones which are AC coupled at the input.
Spectrum analyzers (in normal sweep) will mirror the signals at 0Hz if you set the start frequency to a negative value. This features is useful when using external mixers or frequency offsets where the frequency axis can show relative negative frequencies.
The 9kHz value is the cut-off frequency of the internal DC blocking capacitor. This is a standard value. Making it less than 9kHz is very difficult while simultaneously meeting the higher bandwidth requirements. Very high performance spectrum analyzers are actually DC coupled and can measure down to 3Hz.
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Very high performance spectrum analyzers are actually DC coupled and can measure down to 3Hz.
But they usually have a big downside: you have to be very careful when measuring with such an instrument as the input stage will be destroyed if you input a dc signal.
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#25 Reply
Posted by
Shock
on 06 Oct, 2014 18:03
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Thanks for the video, I was cheering you on there in the middle when you faltered, but you came through in the end and nailed it, well done.
Often when we sleep on it things become clearer. I think you have got the gear and the knowledge to never back down from a challenge now.
Don't worry about the length of the videos you can always throw some quick ones in. There is no harm in making them episodic, as long as we don't have to wait.
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#26 Reply
Posted by
Hugoneus
on 06 Oct, 2014 22:46
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Very high performance spectrum analyzers are actually DC coupled and can measure down to 3Hz.
But they usually have a big downside: you have to be very careful when measuring with such an instrument as the input stage will be destroyed if you input a dc signal.
Yes, these instrument have a big label at the input connector warning the user that only 0-VDC is allowed.
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#27 Reply
Posted by
G0HZU
on 06 Oct, 2014 23:20
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If the 10dB (or more) attenuator is selected I think the DC tolerance goes up to several volts but it isn't wise to chance this!
For my old 22GHz HP8566B I bought a high quality DC block (N type) that works from about 100kHz to 18GHz. It wasn't cheap but it does prevent damage from external DC.
At my place of work, the most common way that uW spectrum analysers get damaged is from external DC rather than from high RF power.
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#28 Reply
Posted by
all_repair
on 06 Oct, 2014 23:44
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When the content is there, length is not a problem. Each and every video of yours, no skip or fast forward when I was watching with full attention.
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#29 Reply
Posted by
Hugoneus
on 07 Oct, 2014 00:41
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If the 10dB (or more) attenuator is selected I think the DC tolerance goes up to several volts but it isn't wise to chance this!
For my old 22GHz HP8566B I bought a high quality DC block (N type) that works from about 100kHz to 18GHz. It wasn't cheap but it does prevent damage from external DC.
At my place of work, the most common way that uW spectrum analysers get damaged is from external DC rather than from high RF power.
Yes, this is indeed a problem in many places. While I was doing my Ph.D., another graduate student accidentally screwed an SMA into a V connector on a VNA. It was a thread-on-thread mess and the whole connector needed to be replaced. Another time, a student put 8V on the input of a 70GHz sub-sampling scope module, killing it instantly.
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#30 Reply
Posted by
dentaku
on 07 Oct, 2014 02:50
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I would be interested in seeing a video explaining PLLs.
If you haven't watched Alan W2AEW's video on PLL already I would suggest you don't so you're not influenced by his really excellent demonstrations then see how your method of explaining it differs.
then you can watch the W2AEW video after you've done editing yours
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#31 Reply
Posted by
ivaylo
on 07 Oct, 2014 06:05
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Yes, don't change anything. Your videos are excellent!
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Another time, a student put 8V on the input of a 70GHz sub-sampling scope module, killing it instantly.
Thanks for answering my previous questions.
One has to wonder, why HP would not install a DC block at the manufacturing level.
Why is there even a DC input path open, if it is so dangerous for the instrument?
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#33 Reply
Posted by
Hugoneus
on 07 Oct, 2014 14:48
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Another time, a student put 8V on the input of a 70GHz sub-sampling scope module, killing it instantly.
Thanks for answering my previous questions.
One has to wonder, why HP would not install a DC block at the manufacturing level.
Why is there even a DC input path open, if it is so dangerous for the instrument?
Well, for the PXA/PSA with a 3Hz low-frequency limit, they have no choice. There is no way to meet 3Hz low cut-off and 50GHz high cut-off simultaneously.
As for the scope module, it has to be DC coupled, because it is suppose to measure DC offsets. It was just rated to only 5V and not 8V.
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#34 Reply
Posted by
vaualbus
on 07 Oct, 2014 22:24
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Do you know how on the new agilent/keysight spectrum analyzer can achive a range from 3Hz to 50Ghz?
What could are the differences between the SA you bought and the new agilent models?
Best regards, Alberto.
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#35 Reply
Posted by
mhuffman77
on 07 Jan, 2016 20:16
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Bump on this topic. Any chance you could scan and upload the Schematic you are using. Schematic #E4403-60057? Great video, thank you very much for recording and sharing this. I watched it from end to end yesterday trying to repair an E4403B with an LO unlock failure. Unfortunately I received erroneous readings at the pretune circuit so we I had to part ways there in terms of failure. Pretty much dead in the water without that schematic.
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#36 Reply
Posted by
smgvbest
on 26 Aug, 2018 19:27
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#37 Reply
Posted by
mbielman
on 23 Mar, 2022 22:55
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Our E4407B at work developed an "LO Unlocked" error and decided to take a look. I have repaired two ESA's with this problem, same IC as in Signal Path repair videos. But when I started looking at the RF Deck PCB, it's different! Labeled as p/n E4403-20100. The divider chain has different parts. Uses an Agilent 1GC1-4210 divider (similar to HMC862) divide by 2/4/8/16 I believe, selectable via 3 inputs. It's driven by a differential receiver/driver MC10EL16.
CANNOT find a CLIP for this one!
But the MC10EL16 has 0 dBm coming in, and -15 dBm coming out.
Looks suspicious!
Mark
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#38 Reply
Posted by
mbielman
on 24 Mar, 2022 01:45
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Correction: I think E4403-20100 might be the blank PCB.
The label on the PCA is E4403-60107. But NOT in the CLIP.
Mark
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#39 Reply
Posted by
DavidAlfa
on 14 Mar, 2023 05:27
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#40 Reply
Posted by
anotherlin
on 14 Mar, 2023 13:03
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Does anyone where to find the schematics shown in the video?
Try artekmanuals.com, but it's not free. They have the component level manual for E440xB.
I've not tried for that model in particular. But I've bought quite a few manuals for Tektronix plug-ins, the scans are really excellent, worth the money.
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#41 Reply
Posted by
vaualbus
on 24 Apr, 2023 09:41
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Indeed it would cool to have his copy too as his version apparently were digital all the time, the artekmanual version is the scanned manual.
Note the artekmanuals now is a little bit slow as the owner just recently passed away.
Them business is now handled by his wife but for now only the bay store is handled due to IT problems apparently.