Teardown, Repair & Analysis of an Agilent E4443A 3Hz - 6.7GHz Spectrum Analyzer - Page 1
Forum section: electronics / testgear

author: Hugoneus
author_rank: Frequent Contributor
timestamp: October 10, 2017, 07:55:58 pm
content: You can watch the video here: [54 Minutes]youtu.be/i2BU5sVgHvQMore videos at The Signal Path:www.TheSignalPath.com

author: technogeeky
author_rank: Frequent Contributor
timestamp: October 10, 2017, 08:07:23 pm
content: Quote from: Hugoneus on October 10, 2017, 07:55:58 pmGreat video again, as always. Who else repairs things with their mystery box parts instead of finding the original?You are the person who makes me the happiest I provide what little patreon support I can.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: October 10, 2017, 10:32:28 pm
content: Quote from: technogeeky on October 10, 2017, 08:07:23 pmThank you for supporting me. It makes these repairs possible!

author: TheSteve
author_rank: Unknown
timestamp: October 10, 2017, 10:59:23 pm
content: I believe you mentioned the final amp was labeled "S1" - is it possibly a Sirenza Microdevices SNA-176?

author: Hugoneus
author_rank: Frequent Contributor
timestamp: October 10, 2017, 11:07:41 pm
content: Quote from: TheSteve on October 10, 2017, 10:59:23 pmIt could have been! How did you find it?!

author: TheSteve
author_rank: Unknown
timestamp: October 10, 2017, 11:32:45 pm
content: Quote from: Hugoneus on October 10, 2017, 11:07:41 pmI used my magic 8-ball.No actually I just googled for MMIC and S1I believe you said it had 50 ohm bias resistor - that would mean the voltage supply was likely around 7 volts, is that correct?

author: Neganur
author_rank: Unknown
timestamp: October 11, 2017, 05:12:32 am
content: Sirenza sounds correct from memory, I can't find the folder with the schematic I derived anymore.Had a couple of those A9 boards. You can still buy the DRO from Elcom by the way - $2000 is what their quote said (the Keysight repair/replace price for the whole board was some 3.3k iirc). So the fix is cheaper if the phase noise isn't compromisedOpening the lid of that DRO is totally worth the look imo!

author: Cubdriver
author_rank: Unknown
timestamp: October 11, 2017, 05:28:51 am
content: Once again, an excellent and engaging video, Shahriar. Nicely done, as usual.-Pat

author: technogeeky
author_rank: Frequent Contributor
timestamp: October 11, 2017, 05:33:15 am
content: Quote from: Neganur on October 11, 2017, 05:12:32 amIs the overall phase noise of the E4443A still world class or something? I would guess without digging into datasheets that his Keysight EXA is better in almost every way.

author: Neganur
author_rank: Unknown
timestamp: October 11, 2017, 08:26:04 am
content: Actually no, the EXA is a lower tier category (Entry vs. Performance) even though it is of the X-series (BSA->CXA->EXA->MXA->PXA->UXA something like 'basic' 'entry' (low cost) 'mid' 'performance' 'high performance' )The UXA (similar to PXA) is mainly a lot faster, more BW (especially a lot wider real time BW), a lot more SW bells and whistles, also connectivity since USB on the PSA is an option (but has LAN) and the phase noise is pretty spectacular compared to the older performance PSABut then again the UXA is not something I could afford, the PSA is very good compared to all of the other typical 'legacy' spectrum analyzers (HP 859X 856X ESA etc, the Rigols are not even worth mentioning)

author: Hugoneus
author_rank: Frequent Contributor
timestamp: October 11, 2017, 03:38:28 pm
content: I have done extensive reviews for both the EXA and MXA-B on my website. You can see the differences in performance between them.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: October 12, 2017, 05:46:34 pm
content: Quote from: TheSteve on October 10, 2017, 11:32:45 pmNice find! Thanks.

author: CNe7532294
author_rank: Regular Contributor
timestamp: October 13, 2017, 12:32:35 am
content: Quote from: Neganur on October 11, 2017, 05:12:32 amWOW.I'm even more shocked.I'll say what I said on youtube as well.The part itself is subpar to be installed on an Agilent/Keysight unit. A unit that could be destined for use in critical applications. The military or satellite/comms troubleshooting in NASA or SpaceX to name a few.Its not hermetically sealed first of all. Therefore O2, CO2, and H2O can get in. There are no gold plated copper traces. Its just the bare copper therefore its gonna tarnish from said molecules in the air. Then there is the PCB substrate instead of ceramic Alumina for the substrate. The amplifier failing was no surprise. The inside must be like an oven to it. Death by heat exhaustion or stroke. Laminated fiberglass is not the way to conduct heat to the metal housing.....What in the world was Agilent or Elcom thinking? Poor undersight, cost cutting, or engineered to fail?Back in the day an assembly like this was done right by being sealed with o-rings or a rubber seal, nitrogen purged/assembled in a positive pressure container, the circuit was ceramic based with gold plated traces and gold bond wires ultrasonic welds instead of solder for connections. How times have changed...Picture attached is from a 87405A preamplifier. Its a prime example of what I mean. Seen are the gold plating, the ceramic subtrate, and the bond wiring. Unseen, is the cover with the rubber seal. I have a vid and can post pictures from a 85644A low band assembly as well. Same thing. The exception is that its not sealed.All in all great repair on the spot with what you've got.My question is, are your components are able to handle the heat for long term use?EDIT: added comparision picture and extra rant.

author: 1design
author_rank: Regular Contributor
timestamp: October 13, 2017, 06:56:31 am
content: Absolutely no need for bonding and alumina at these low frequencies. I used the TSM-DS3 at E band frequencies and it still worked well.If you go for a metal backed substrate and add a few copper filled vias you can get rid of a lot of heat for very little money. The PA we used dissipated 3W in WLCSP package and we still managed to cool it down appropriately with this method. The substrate was 100um thick though.I completely agree with you in regards to plating, the filter should have been gold plated to prevent oxidation. Maybe you can measure its S parameters and lets see if we can replace it with a few mini-circuits parts

author: CNe7532294
author_rank: Regular Contributor
timestamp: October 13, 2017, 03:14:36 pm
content: Quote from: 1design on October 13, 2017, 06:56:31 amYour first point is interesting and I have questions about that. True you can get away with material using laminated fiberglass. I've seen parts like microwave couplers designed exactly like the filter seen on the vid (bare copper, fiberglass laminate) and currently there are actives installed on this substrate from components here and there. However I still have doubts about the material.Mainly for long term use.Here are my questions.Did your design have other assemblies or components close to it generating heat that would need to be dissipated as well?Here in the vid we clearly see the Elcom part sandwiched between 2 boards possibly generating heat. It does have free space between the boards for airflow though. Then there are boards opposite and adjacent to the microwave side on the part itself.An important question is how long did your design last or rather intended it to last?As mentioned, you can get away with this thermal design if you don't use it heavily and expect it to last for a certain occasion.Basically we both know the point here is pricing and cost. For that reason I currently still have to stand by my comment that it is subpar.Why would I pay $2,000 or $3,000 for a part that substandard for the Agilent brand, a SA unit that still runs for $10,000+ used at least, and its potential use in high stakes environments as stated above? When I think of HP/Agilent/Keysight, I think of reliability. If this part was brought down to $1000 or rather under that I would maybe consider it. I also think its just plain insulting to recommend the same part that will fail as the replacement. Its as insulting as the Nvidia mobile video chip fiasco back in the late 2000s. See service note.http://literature.cdn.keysight.com/litweb/pdf/E4443A-19.pdfThere is a use for this however and not completely all bad. I could see this unit from Elcom being put to use in space but only because there is vacuum up there and it is cold. Just because I labeled it subpar does not mean it is subpar in general. It is only subpar because of how it was applied. Specs provided courtesy of Elcom Tech and Shahriar. Notice the operating temperature range.http://www.fei-elcomtech.com/assets/s-1006a-fei-elcom-datasheet-(mar-20%2C-2014).pdfAgreed for sure on the gold.That was the most shocking considering the price for replacement. As for S parameter, a VNA set was the one thing I had to put off for my collection.The grounds would quake and crumble, fire and brimstone would try to rise up from below and would rain all over for taking the sacred rock called "house space"if you know what I mean (+1 if you can get the tv series reference, hint: abc). This is also why I got a 8563E vs the 8566B as my main SA for use. If anyone is able to do S-Parameter measurements, I'd be interested in the results as well.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: October 13, 2017, 05:36:42 pm
content: Interesting discussions.I was so curious about this issue that I went and bought another one of those LO modules from eBay. It was listed as unknown condition and when I measured its output was at -8dBm. Undoubtedly a similar problem.I wonder how much interest there is in me fixing the other one through some plating technique.By the way, in the one that I fixed in the PSA, I used two amplifiers after the mixer. The second one operates (somewhat) in compression and so even if the input to the whole chain degrades a little, the output will remain fairly constant in power.

author: SeanB
author_rank: Super Contributor
timestamp: October 13, 2017, 06:54:18 pm
content: If you are going to re plate I would suggest silver, and then a thin conformal coat over it, or just polish the filter copper and apply the thin conformal coat to it.

author: texaspyro
author_rank: Super Contributor
timestamp: October 13, 2017, 09:46:25 pm
content: There is a product called Cool Amp. It is a powder that you mix with hot water and rub onto well cleaned copper. It plates a (very thin) layer of silver onto the copper. The layer is thin enough that you can sort-of see the copper underneath the plated layer. The layer is thin because it only reacts with copper and as the silver builds up it stops plating additional material.Brush plated gold or silver will plate a thicker layer of material, but the plating voltage might not be good for the surrounding electronics. There all lots of gold brush plating kits available that are used to repair printed circuit board edge connectors.A conformal coat on a microwave device is probably not a good idea...

author: CNe7532294
author_rank: Regular Contributor
timestamp: October 14, 2017, 09:43:08 pm
content: Quote from: SeanB on October 13, 2017, 06:54:18 pmReplating with silver is good. Not the best like gold but better than no plating. Conformal coating is a bad call. Microwave circuits (in this case 3.6GHz) are subjected to things like skin effect. Also theres an article I read somewhere about the percentage of water retention going up with coating vs no coating at all. H2O tends to get trapped in the coating somehow. Water no matter how small is a big no-no we'd like to avoid.Quote from: texaspyro on October 13, 2017, 09:46:25 pmAgreed. This can be a solution.Quote from: Hugoneus on October 13, 2017, 05:36:42 pmIt wouldn't hurt. What @texaspryo said was best. Tinning the trace was a great idea if left with nothing else but I would bet it would change its luster and other properties along with it over time plus its currently an uneven surface. Studies have been done on solder joints mainly but it applies here too. How long this change would occur I really can't say. It depends on the user and the environment. The harder anyone uses this instrument, the more it'll degrade due to microscopic cracking. This results from constant on/off cycles. Metal expanding in heat then contracting when cooled. Link to this study.https://nnsa.energy.gov/sites/default/files/ase/files/1-3-Holm.pdfThe other option, alot of work and only included to give an idea in future designs, would be to keep the bare copper but somehow machine in a "purge port". Alternatively you could assemble the part in a positive pressure "hood" or container of nitrogen. Both cases require creating a close to air tight seal between the covers and housing. An early HP YIG (5086-7781) I pulled from a HP 8561B had this design. Notice the screw port in the middle of the bias/opamp board. Using ebay photo since I can't find my own photos.You can displace any oxygen containing air with nitrogen. I had done this mainly for night vision (PVS-14s) of all things but mainly for water vapor issues (fogging). It would still be able displace oxygen and carbon dioxide. The downside to this would be that this would add to the to-do checklist on maintainance for the unit. Nitrogen and air tends to go to equillibrium eventually (nothing really has a perfect seal).Heat is also a concern as mentioned. But unfortunately there is nothing that can be done about that at this point unless you would want a major overhaul of the unit. The filter portion would be okay if the above are taken care of but the poor transistors would be cooking good. Typically I alway see actives being the point of failure if someone doesn't inject too strong of a signal or there is some good protection against that. This is due to the label "aging" which I translate to heat over time. Technically its not bad if an instrument was designed for 10 years and failed a little over that.At this point I'll be "splitting hairs" (paraphrasing a fellow electronics youtuber).The laminate they are on top of I do not trust. If this were the design stage, that would be replaced with ceramic. The board in the back is contributing to heat as well and I would put insulating material between it and the side of the case closer to the microwave portion. Then I would put thermal conductive padding on any area running hot to the screw-on-cover on that side. I'd also seal up those holes that feed thru the bias to the unpopulated transistor areas. At this time, you'll have to leave it alone and keep note of it. Maybe fix up the circuit with proper discrete components if you would want that.The more and more I look at that part and think over it, the more I'm convinced this was mainly designed to be included into something which would shoot high in the sky then orbit over our heads. Any earth bound application is an after thought. I wonder how much it weighs. Nothing on the spec sheet for that. Notice that SATCOM is even in all caps on the datasheet. The attention getter for whom they were truly marketing to. I just wonder what they were thinking when designing the SA.This much lack of attention to detail makes no sense. Me thinks either someone at Elcom got greedy and did some sweet talking (see mentioned applications on datasheet) or someone at then Agilent slammed their fists hard against the table and said "WE MUST HAVE THIS SAT PART FOR OUR NEW INSTRUMENT!" and so it was done. Maybe both. Someone was caught with their pants down.TL;DR a.k.a. Summary:Go ahead for plating the other unit with preferably gold to get rid of the oxidation problem. Fix up the 3.6GHz amplifier section with the proper discretes (mainly the resistor and the feed thru for the bias). Maybe find something that can run in a hotter environment. Nothing else can be done about the heating issue at this point unless you've got something on hand. Just going to have to note and monitor this part over time.Adjustments to any of the above are up to you. I'll respect your decision in any case. Thank you for providing this teardown.

author: texaspyro
author_rank: Super Contributor
timestamp: October 14, 2017, 10:11:12 pm
content: Here is a place that sells a PCB repair kit for lotsa bucks (but less than others). They have a video showing how to use it.http://www.soldertools.net/products/Gold-Contact-Replating-Kit.htmlThey also sell the chemicals for a LOT less. You would need a power supply (something tells me that's not going to be a problem). I have seen people use a carbon rod with a swab head for the wand. I've heard stainless steel also works...

author: 1design
author_rank: Regular Contributor
timestamp: October 15, 2017, 03:04:41 pm
content: The material I mentioned is not a laminated fibreglass like the FR family of laminates. It is a ceramic-filled reinforced material with high thermal conductivity.Also, the substrate itself is just one part of the thermal design, parts usually have thermal pads. When you connect those to the base with copper filled vias that are 100um wide in a 100um thick material you get very good thermal and electrical performance.The design was a mmW radio front end, designed to work outdoor at up to +55degC of ambient temperature.And yes, there we other component heating the unit. Mostly the modem, ADCs and the 2GHz BW baseband VGAs.We did extensive simulations and post design testing(thermal cycling for accelerated aging from -33degC to +55degC in 2 hour cycles) to confirm it would work in mass production, all SMT of course.In my humble opinion chip and wire is OK for very high end or low cost(packing to expensive, LCD displays for example), in between it just doesn't make the cut.