It’s so crazy, that’s still a $40,000-$70,000 Spectrum Analyzer. Not just anyone is going to take on a piece of kit like that. You do excellent work and explain it well. thanks for the video.
I so enjoy watching someone of your skill set, who's day job involves bleeding edge research, that still enjoys getting your hands dirty fixing equipment. And your explanations are so clear. The subject is often over my head and yet I can understand your explanations. You have a gift.
Thank you once again for showing us your thought process! I legit got nostalgia when you upload another HP/Agilent equipment repair vid, it is precious. Cannot wait for part 2!
Thanks, Shahriar for making these educational (on many levels) videos and explaining how so many "black" boxes are designed and constructed, allowing the possibility of repairs. On another level showing how using a methodical and intelligent approach is very efficient and being rewarded with a mostly working instrument.
We had the 6GHz model at the radio club with some similar sounding faults and our diagnosis was a faulty highband mixer and no budget for replacing it. Couple of steps on the frontend attenuator did not actuate either, but the RF side was electrically fine. It was given away as a parts machine in frustration and to regain the space it took.
Attennutator problems are the best problems to fix. :) I cleaned the attennuator pads on my 8566B, then it was just like new. One of the common problems of the E4406A and E4448A series is that the CCFL tube backlight dims and the light diffuser panel behind the LCD turns to yellow. You can order new CCFLs for a few dollars and do a replacement, it is worth it. Screen becomes much brighter. Or as an alternative you can connect to an external VGA display and have a much better picture, but mine radiates around -80db at 72 Mhz, and it becomes visible on the analyzer.
I thought I had seen an LED replacement for the CCFL, but I can't find it now. I use a 7 inch external VGA display on my E4406A, but I'd prefer to have the LCD working again. I haven't noticed any spurious signals but then I rarely use it below 2 GHz.
yes please part 2 -- great repair, good to know that the attenators are sometimes repairable. I assume someting in the YIG YTF after the RYTHM switch because it disappears at 2.85GHz (assume) till half of the spectrum width e.g. 26ghz. The SBTX Path for >26Gz till 50 Ghz path seems to work.So could be the YIG preselector or the follow up mixer. with 3-7GHz LO , also that could be a problem. So measure at coax W17 first.
Always enjoy your repairs bu this one even more becaise of the initial transistor repair. I did a similar one on my HP 8350 regulator board since i did not want to take it apart but always considered a noob lame repair. Thanks
Great troubleshooting work, narrowing down the PSU issue to the SBTX. Wish I had time to record my repairs; I recently picked up an E4448A and rebuilt the 2 attenuators, along with a flaky 50 GHz transfer switch for opt 110 (full band preamp). Btw the attenuators can be fully disassembled down to the plungers to replace the o-rings. I've done 26.5 GHz and 50 GHz units, all pass cal at Roseville. As far as signals disappearing > 3 GHz; try using the "Preselector Center" key in the amplitude menu. The PSA manual recommendeds applying this setting for measurements > 2.85 GHz. If you cannot manually adjust the preselector and get a signal between 2.85 to 26.8 GHz, the RYTHM (also a part of the SBTX "tower") might be the culprit. Try measuring where W17 connects on the tower. I have seen an SBTX tower repair service on eBay for roughly $1700 flat rate. Usually this is for units that experience amplitude drop in highband due to excessive preselector drift that cannot be adjusted using N7800. Maybe the repair also covers adjustment of the RYTHM YIG and SBTX? A new 50 GHz tower is around $18K from Keysight last time I checked... Btw, above 26.8 GHz, the highband preselector and mixer use Barrium Ferrite instead of YIG. BaFe has much higher magnetic permeability than YIG so the magnetic field required is a lot smaller for higher resonant frequencies. Pretty cool patent by Hassan Tanbakuchi...
I should be doing other things, but a TSP video means everything stops! I need to fix one of my ESG series signal generators with an amplifier UNLEVEL fault, so it's time to rewatch your E4433B repair vids.
Great work, but it seemed that this is the problem of power supply. Yes, I also thought that the attenuers would not repair. Thank you. I'm waiting for the second part.
*Agilent 50GHz PSA (E4448A) Spectrum Analyzer Teardown & Repair - Part 1* * *0:10** Initial Problem:* The Agilent E4448A spectrum analyzer (up to 50GHz) exhibited intermittent power-on issues, often shutting down during boot. * *1:12** Internal Inspection:* The analyzer uses a triple conversion superheterodyne architecture. Initial suspicion fell on the power supply or the power switch. * *2:17** Power Switch Verification:* The service manual revealed a straightforward power-on sequence involving MOSFETs. The front panel switch was confirmed to be functioning correctly. * *3:38** Power Sequencing Investigation:* Further probing indicated that the power supply was likely being overloaded, causing the shutdown. * *5:52** Isolating the Fault:* Disconnecting assemblies one by one revealed that the dual YIG pre-selector assembly (A19) was the likely culprit. * *6:57** Pinpointing the Issue:* Further isolation pointed to a potential issue with the YIG pre-selectors themselves or their driver circuitry. * *7:55** YIG Pre-selector Details:* The A19 assembly contains two YIG pre-selectors covering different frequency bands (millimeter wave and high band). High currents through the YIG coils were a potential concern. * *8:17** Evidence of Prior Repair:* The analyzer showed signs of a previous repair attempt, with improperly tightened coaxial cables and a concerning proximity of coil wires to the chassis. * *9:27** Short Circuit Found:* A short circuit was discovered between one of the YIG coils and the chassis, likely explaining the intermittent power issues. * *10:06** Reassembly and Testing:* After insulating the shorted coil, the analyzer successfully booted and completed its internal alignment procedures. * *11:12** Attenuator Step Error:* An "attenuation steps error" was encountered, a common issue in older spectrum analyzers due to failing electromechanical attenuators. * *11:39** Attenuator Testing:* Using a Keysight FieldFox, the attenuator was tested across its frequency range (DC to 50 GHz), revealing that the 20dB and 30dB attenuation paths were faulty at lower frequencies due to poor contact. * *13:25** Attenuator Repair:* The attenuator was disassembled, and the individual attenuation pads were carefully cleaned to improve contact. * *18:12** Lid Details:* The attenuator lid features RF absorbers, gaskets for RF sealing, and adjustable screws that likely serve as fine-tuning elements for the frequency response. * *19:16** Second Test and Result:* After reassembly, the attenuator functioned correctly across its entire range. The alignment errors were also resolved. * *20:19** Remaining Issues:* Despite the fixes, certain frequency bands still failed to measure correctly, suggesting problems with the front-end YIG switching or mixers. * *20:41** Conclusion of Part 1:* The video concludes with a preview of Part 2, where the remaining frequency band issues will be investigated. I used gemini-1.5-pro-exp-0827 on rocketrecap dot com to summarize the transcript. Cost (if I didn't use the free tier): $0.03 Input tokens: 22922 Output tokens: 672
I've had an interest in electronics for most of my life. Being raised in a lower middle-class family, i didn't have the means to let the hobby really take off. But as an adult i've had the chance to start putting some money into it. I just bought my first scope not long ago. I have a rigexpert AA-600 for my antenna tuning. And some other odds and ends on my tiny little work bench. I'd give body parts to own some of the equipment i see people working with on youtube. Especially the high end "costs as much as a car" kind of equipment. I'll never be able to own stuff like that.
Everyone who gets into the electronics hobby suffers from gear envy at one time or another, but truthfully, if you've got a couple of decent power supplies, a modest oscilloscope, a couple of multimeters, some good quality soldering equipment and a handful of specialty tools that suit your specific interests, then you've got what you need. Heaven knows I salivate every time I see a wide shot of Shahriar's lab, but honestly, I wouldn't know what to do with 90% of his equipment. I'd probably sell most of it to finance a lavish retirement!
We have a couple spec-ans at work that are similar and failed calibration on certain bands, I have a feeling they've got similar issues to this one. I am definitely not allowed to open them to try to fix them though xD
Excellent video! I like how you layout your thought process clearly and prove it through experiments. I hope it's not the YTX or what is called on your unit. It's prohibitively expensive to replace. I had one with a broken rod that holds the YIG balls. It could be remounted and tuned by some very experienced folks with special equipment but it's $$$. The other time I was lucky on another HP SA where the 2-22Ghz bands were dead but lower band works. It turned out that the power transistor on YTX driver was dead so that the YTX preselector is not being driven. Much cheaper to repair comparing to a broken YTX. Looking forward to your next episode!!!
Wow 50Gig! Where did it come from... how much did it cost?. How lucky was that find... Anyone else it would be junk because we wouldn't have a chance of fixing it.
OMFG!!! I actually understood 100% of this video on the first pass!!! Normally I have to pause / rewind / rewatch a few bits to give my brain time to 'catch up', but not this time... Either I am learning more, or Shahriar is slowing down as he gets older...
These are the type of videos I really enjoy watching.
It’s so crazy, that’s still a $40,000-$70,000 Spectrum Analyzer. Not just anyone is going to take on a piece of kit like that. You do excellent work and explain it well. thanks for the video.
HP 8566&8568 is $500 on ebay with a little luck, nowadays.
Plenty enough for most simple tasks
@@hinz1 Year back, I paid $55K for my 8566, ouch! Seeing what they go for now is just crazy.
(years) that was back in 84/85
I so enjoy watching someone of your skill set, who's day job involves bleeding edge research, that still enjoys getting your hands dirty fixing equipment. And your explanations are so clear. The subject is often over my head and yet I can understand your explanations. You have a gift.
My favorite type of TSP video. Thanks for posting this.
This is a bit above my head, but it is a lot of fun to watch someone who knows what they are doing working on such specialized equipment.
Thank you once again for showing us your thought process! I legit got nostalgia when you upload another HP/Agilent equipment repair vid, it is precious. Cannot wait for part 2!
we had 4 pcs of #4448A in our calibration lab during my time in Keysight Russia. All PSGs adjusted using this spectrum analyzer
Thanks, Shahriar for making these educational (on many levels) videos and explaining how so many "black" boxes are designed and constructed, allowing the possibility of repairs. On another level showing how using a methodical and intelligent approach is very efficient and being rewarded with a mostly working instrument.
We had the 6GHz model at the radio club with some similar sounding faults and our diagnosis was a faulty highband mixer and no budget for replacing it.
Couple of steps on the frontend attenuator did not actuate either, but the RF side was electrically fine.
It was given away as a parts machine in frustration and to regain the space it took.
Always enjoyable to watch your analysis to find the fault. Incredible skill required to fix and re-assemble the attenuator.
Nice, finally one where it's not just a dead LDO somewhere, yet you managed to get somewhere without any special parts
Your happiness is contagious. Good job! 👍
One of the best channel for great learning 🎉🎉🎉
The repair steps seem very clear, organized and logical until you try it yourself 😨
Attennutator problems are the best problems to fix. :) I cleaned the attennuator pads on my 8566B, then it was just like new. One of the common problems of the E4406A and E4448A series is that the CCFL tube backlight dims and the light diffuser panel behind the LCD turns to yellow. You can order new CCFLs for a few dollars and do a replacement, it is worth it. Screen becomes much brighter. Or as an alternative you can connect to an external VGA display and have a much better picture, but mine radiates around -80db at 72 Mhz, and it becomes visible on the analyzer.
I thought I had seen an LED replacement for the CCFL, but I can't find it now. I use a 7 inch external VGA display on my E4406A, but I'd prefer to have the LCD working again. I haven't noticed any spurious signals but then I rarely use it below 2 GHz.
yes please part 2 -- great repair, good to know that the attenators are sometimes repairable. I assume someting in the YIG YTF after the RYTHM switch because it disappears at 2.85GHz (assume) till half of the spectrum width e.g. 26ghz. The SBTX Path for >26Gz till 50 Ghz path seems to work.So could be the YIG preselector or the follow up mixer. with 3-7GHz LO , also that could be a problem. So measure at coax W17 first.
I agree! Thanks :)
Another Great Video... Looking forward to Part 2, the hard part. ;)
Excellent video as always, thanks. Sure wish you would do the Part 2 of the Siglent SNA5000 review soon.
Excellent video.
Thanks for posting it.
Always enjoy your repairs bu this one even more becaise of the initial transistor repair. I did a similar one on my HP 8350 regulator board since i did not want to take it apart but always considered a noob lame repair. Thanks
Great troubleshooting work, narrowing down the PSU issue to the SBTX. Wish I had time to record my repairs; I recently picked up an E4448A and rebuilt the 2 attenuators, along with a flaky 50 GHz transfer switch for opt 110 (full band preamp). Btw the attenuators can be fully disassembled down to the plungers to replace the o-rings. I've done 26.5 GHz and 50 GHz units, all pass cal at Roseville.
As far as signals disappearing > 3 GHz; try using the "Preselector Center" key in the amplitude menu. The PSA manual recommendeds applying this setting for measurements > 2.85 GHz. If you cannot manually adjust the preselector and get a signal between 2.85 to 26.8 GHz, the RYTHM (also a part of the SBTX "tower") might be the culprit. Try measuring where W17 connects on the tower.
I have seen an SBTX tower repair service on eBay for roughly $1700 flat rate. Usually this is for units that experience amplitude drop in highband due to excessive preselector drift that cannot be adjusted using N7800. Maybe the repair also covers adjustment of the RYTHM YIG and SBTX? A new 50 GHz tower is around $18K from Keysight last time I checked...
Btw, above 26.8 GHz, the highband preselector and mixer use Barrium Ferrite instead of YIG. BaFe has much higher magnetic permeability than YIG so the magnetic field required is a lot smaller for higher resonant frequencies. Pretty cool patent by Hassan Tanbakuchi...
Thanks for your comment! Would you mind dropping me an email?
@@Thesignalpath Sent. Hopefully I have the right address (gmail on the signal path site "about" page)
I'm not smart enough to have any suggestions, but I love these videos! 😀
I should be doing other things, but a TSP video means everything stops! I need to fix one of my ESG series signal generators with an amplifier UNLEVEL fault, so it's time to rewatch your E4433B repair vids.
Great work, but it seemed that this is the problem of power supply.
Yes, I also thought that the attenuers would not repair.
Thank you. I'm waiting for the second part.
*Agilent 50GHz PSA (E4448A) Spectrum Analyzer Teardown & Repair - Part 1*
* *0:10** Initial Problem:* The Agilent E4448A spectrum analyzer (up to 50GHz) exhibited intermittent power-on issues, often shutting down during boot.
* *1:12** Internal Inspection:* The analyzer uses a triple conversion superheterodyne architecture. Initial suspicion fell on the power supply or the power switch.
* *2:17** Power Switch Verification:* The service manual revealed a straightforward power-on sequence involving MOSFETs. The front panel switch was confirmed to be functioning correctly.
* *3:38** Power Sequencing Investigation:* Further probing indicated that the power supply was likely being overloaded, causing the shutdown.
* *5:52** Isolating the Fault:* Disconnecting assemblies one by one revealed that the dual YIG pre-selector assembly (A19) was the likely culprit.
* *6:57** Pinpointing the Issue:* Further isolation pointed to a potential issue with the YIG pre-selectors themselves or their driver circuitry.
* *7:55** YIG Pre-selector Details:* The A19 assembly contains two YIG pre-selectors covering different frequency bands (millimeter wave and high band). High currents through the YIG coils were a potential concern.
* *8:17** Evidence of Prior Repair:* The analyzer showed signs of a previous repair attempt, with improperly tightened coaxial cables and a concerning proximity of coil wires to the chassis.
* *9:27** Short Circuit Found:* A short circuit was discovered between one of the YIG coils and the chassis, likely explaining the intermittent power issues.
* *10:06** Reassembly and Testing:* After insulating the shorted coil, the analyzer successfully booted and completed its internal alignment procedures.
* *11:12** Attenuator Step Error:* An "attenuation steps error" was encountered, a common issue in older spectrum analyzers due to failing electromechanical attenuators.
* *11:39** Attenuator Testing:* Using a Keysight FieldFox, the attenuator was tested across its frequency range (DC to 50 GHz), revealing that the 20dB and 30dB attenuation paths were faulty at lower frequencies due to poor contact.
* *13:25** Attenuator Repair:* The attenuator was disassembled, and the individual attenuation pads were carefully cleaned to improve contact.
* *18:12** Lid Details:* The attenuator lid features RF absorbers, gaskets for RF sealing, and adjustable screws that likely serve as fine-tuning elements for the frequency response.
* *19:16** Second Test and Result:* After reassembly, the attenuator functioned correctly across its entire range. The alignment errors were also resolved.
* *20:19** Remaining Issues:* Despite the fixes, certain frequency bands still failed to measure correctly, suggesting problems with the front-end YIG switching or mixers.
* *20:41** Conclusion of Part 1:* The video concludes with a preview of Part 2, where the remaining frequency band issues will be investigated.
I used gemini-1.5-pro-exp-0827 on rocketrecap dot com to summarize the transcript.
Cost (if I didn't use the free tier): $0.03
Input tokens: 22922
Output tokens: 672
tnx Shahriar, is there any troubleshooting checklist in your mind that you can share for diagnosing devices such as an oscilloscope
Two more parts please, with more details :)
I've had an interest in electronics for most of my life. Being raised in a lower middle-class family, i didn't have the means to let the hobby really take off. But as an adult i've had the chance to start putting some money into it. I just bought my first scope not long ago. I have a rigexpert AA-600 for my antenna tuning. And some other odds and ends on my tiny little work bench. I'd give body parts to own some of the equipment i see people working with on youtube. Especially the high end "costs as much as a car" kind of equipment. I'll never be able to own stuff like that.
Everyone who gets into the electronics hobby suffers from gear envy at one time or another, but truthfully, if you've got a couple of decent power supplies, a modest oscilloscope, a couple of multimeters, some good quality soldering equipment and a handful of specialty tools that suit your specific interests, then you've got what you need. Heaven knows I salivate every time I see a wide shot of Shahriar's lab, but honestly, I wouldn't know what to do with 90% of his equipment. I'd probably sell most of it to finance a lavish retirement!
@@FlyingShotsman :)
Very interesting video. Please, continue.
We have a couple spec-ans at work that are similar and failed calibration on certain bands, I have a feeling they've got similar issues to this one. I am definitely not allowed to open them to try to fix them though xD
DC and up, nice !
Cat at 20:54
Puch says yes
At 2:31 there is a rectangle on the left under the symbol of C5. What does this rectangle mean?
It’s a three terminal tantalum capacitor. It just says two of its terminals are connected to ground.
@@Thesignalpath Thank you very much.
Excellent video! I like how you layout your thought process clearly and prove it through experiments. I hope it's not the YTX or what is called on your unit. It's prohibitively expensive to replace. I had one with a broken rod that holds the YIG balls. It could be remounted and tuned by some very experienced folks with special equipment but it's $$$. The other time I was lucky on another HP SA where the 2-22Ghz bands were dead but lower band works. It turned out that the power transistor on YTX driver was dead so that the YTX preselector is not being driven. Much cheaper to repair comparing to a broken YTX. Looking forward to your next episode!!!
Wow 50Gig! Where did it come from... how much did it cost?. How lucky was that find... Anyone else it would be junk because we wouldn't have a chance of fixing it.
OMFG!!! I actually understood 100% of this video on the first pass!!! Normally I have to pause / rewind / rewatch a few bits to give my brain time to 'catch up', but not this time...
Either I am learning more, or Shahriar is slowing down as he gets older...
The one who sold the analyzer and watching this video is banging his head against the wall.
50GHz analyzer? Alien tech if you ask me :D
👍👍
Nice one as always! But.... Pooch is getting old :(
Witchcraft