Teardown, Repair and Experiments with the Anritsu 37347A 20GHz Network Analyzer - Page 1
Forum section: electronics / repair

author: Hugoneus
author_rank: Frequent Contributor
timestamp: March 11, 2016, 04:15:43 pm
content: Here is the long awaited VNA repair!You can watch it here: [46 Minutes]youtu.be/dwAieDTRMdQMore videos at The Signal Path:http://www.TheSignalPath.com

author: TheSteve
author_rank: Unknown
timestamp: March 11, 2016, 05:36:45 pm
content: Thanks for the video Shahriar, it's a glorious old beast! The PLL issue would be interesting to pursue but being it works fine it is pretty hard to justify.

author: ahakman
author_rank: Regular Contributor
timestamp: March 11, 2016, 07:07:29 pm
content: Where do you manage to find such nice stuff that has relatively minor problems? I'm pretty sure the only way I could ever own a VNA (well, at least to justify the cost to myself) would be to find a broken one and fix it...

author: BFX
author_rank: Frequent Contributor
timestamp: March 11, 2016, 11:43:14 pm
content: I can't believe it againso difficult unit and again so simple repairYou are very lucky manBut thx for video

author: Hugoneus
author_rank: Frequent Contributor
timestamp: March 12, 2016, 12:08:54 am
content: Quote from: BFX on March 11, 2016, 11:43:14 pmYes, it is always luck, all my repairs. There is no other explanation.

author: Earendil
author_rank: Regular Contributor
timestamp: March 12, 2016, 12:44:33 am
content: Quote from: Hugoneus on March 12, 2016, 12:08:54 amLOL.You make it look too easy, that's the problem

author: rx8pilot
author_rank: Super Contributor
timestamp: March 12, 2016, 02:47:38 am
content: Smacked with a PhD and a lot of practical experience. Or luck.Sent from my horrible mobile....

author: kazam
author_rank: Regular Contributor
timestamp: March 12, 2016, 03:57:24 am
content: Nice video, thanks!I never liked the Anritsu VNAs though. The HPs just seemed to stay in cal longer. Inconvenient with mechanical cal kits and a chore.I'm sure it must have been a pretty penny back in -94 to get a 20GHz unit!I must say I enjoy your repair videos the most, it's so satisfying. Great service to the community. I always hope for an RF related problem and not some RTC or PSU triviality.Anyway, here is my idea for a video.Design, manufacture and verification of an impedance transformer. This is very basic stuff but a lot of the comments seem to display a lack of knowledge of what you would use a VNA for. Qucs could be used for the design as you probably want to stay with free tools.Almost everyone knows of 50 and 75 ohm cables though and this would be an easy introduction to characteristic impedance, or as it was historically known, surge impedance. If you design for 500MHz you could possibly even demonstrate in time domain. This is something even experienced microwave designers sometimes struggle with as they are so used to frequency domain techniques. I routinely integrate an oscilloscope in my lab setup now to capture waveforms at RF frequencies. Of course this wasn't possible just a few years ago.Just a thought since you seem to like RF equipment!/K

author: bitseeker
author_rank: Super Contributor
timestamp: March 12, 2016, 06:23:44 am
content: Another great instruction and repair video, Shahriar. You do make it look very easy.

author: JoeO
author_rank: Frequent Contributor
timestamp: March 12, 2016, 04:45:54 pm
content: I am not knocking Shahriar or the work he does. He is definitely extremely knowledgeable and competent and really loves what he does.Please remember that youtube video bloggers do NOT have to post all of their videos. They may have many repairs that they can not fix. Those videos may never make it to youtube.Dave seems to post all of his repair videos, the failures and successes. I give him credit for doing that.I just tried to repair a VIZIO flat screen. I looked at many of the VIZIO repairs on Tampatec, Norcal715 and 12voltvids. It wasn't caps and it wasn't the eprom. It is still broken.I can fix about 50% of what I work on. Maybe others have a higher success rate. But youtube is not an accurate representation of reality.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: March 12, 2016, 05:10:01 pm
content: Quote from: JoeO on March 12, 2016, 04:45:54 pmI post 100% of all repairs that I attempt, including the unsuccessful ones like the 600V Matsuada power supply which had potted modules. I simply do not have the time to record something and then not post it. The Signal Path is not my job, I have a whole other full-time career. If I wanted to make money from The Signal Path I would not be making 1 hour technical videos. I spend a large portion of my weekends and sometimes late at night to shoot videos. If anyone wishes to think that after all that work I cherry pick what to post on YouTube, be my guest. Either way it will have zero influence on how I will do things.

author: Earendil
author_rank: Regular Contributor
timestamp: March 12, 2016, 05:27:10 pm
content: Quote from: JoeO on March 12, 2016, 04:45:54 pmSmacking it with your PhD apparently helps

author: vaualbus
author_rank: Frequent Contributor
timestamp: March 12, 2016, 06:21:18 pm
content: Quote from: Hugoneus on March 12, 2016, 05:10:01 pmYou are 100% fine, you even record a video on 25 december! Keep doing good videos.I even think that for all the time you us for doing these video should create a patreon account so people if want, can contribute in your work!.Any ways I think the locking problem is normal operation of the unit.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 12, 2016, 06:35:39 pm
content: Quote from: Hugoneus on March 12, 2016, 05:10:01 pmWhatever your motivation, I will do my absolute best to encourage you to keep sharing. The level of detail and intuition demonstrated is so interesting and useful for me. This holds true for me personally AND professionally. Deconstructing your logic almost always provides guidance for me to better understand my own shortfalls in knowledge. This allows me to better understand what to study, what to experiment on.The experiments that show what an instrument is truly capable of provides a TON of information on the practical nuts and bolts of test and measurement and where it could go wrong. Most educational resources do not get into the level of detail I get on these videos.Many thanks.

author: bitseeker
author_rank: Super Contributor
timestamp: March 12, 2016, 06:42:30 pm
content: Every repair is an adventure and learning opportunity. But I get what Joe is trying to say. Just because you see others successfully repair things, doesn't mean you'll necessarily have the same success rate. So, as always, buyer beware.

author: AF6LJ
author_rank: Unknown
timestamp: March 12, 2016, 07:11:21 pm
content: This is going to be Good.

author: AF6LJ
author_rank: Unknown
timestamp: March 12, 2016, 08:08:09 pm
content: Thanks; this was good and enlightening.

author: TheSteve
author_rank: Unknown
timestamp: March 12, 2016, 10:33:32 pm
content: Shahriar would it possible for you to monitor that PLL at a much higher sample rate to see if it happens to be following a regular pattern or if it is randomly jumping around, or perhaps only locking when a sample is taken?For the others reading this thread - When buying broken equipment to repair you really need to cherry pick only the good stuff. I generally aim for products from companies that offer service manuals, or at the bare minimum a block diagram. It is also good to really focus on the pictures, they can often reveal a lot of information. Such as if someone else has had a go at a repair. I think most of us prefer to not avoid items others have tried to repair(and usually made worse). I've had insanely good luck buying broken items from ebay such as power supplies, a network analyzer, frequency gen, pulse/pattern gen, AWG, DMM's, frequency counters etc. I was able to repair all of them which is very lucky. But it also helps when you have the tools to really troubleshoot items and in many cases with enough experience you may have a good idea of the problem before you even receive it. In Shahriar's case he is not only very very experienced/knowledgeable with electronics he has access to world class test and measurement equipment.

author: bitseeker
author_rank: Super Contributor
timestamp: March 13, 2016, 07:19:17 am
content: Great points, Steve. I'd also add that it's good to do some searching here for the instrument you're interested in and studying up on it, especially what kinds of problems people have encountered and if/how they are addressed.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 13, 2016, 07:24:46 am
content: On this unit, I would be nervous about the HDD going south. Curious what bus it uses and if it can be cloned. On my old PnP machine I converted the HDD to an SSD and made some addl clones to ensure I always have a working image. Not sure it is practical on this VNA.Sent from my horrible mobile....

author: AF6LJ
author_rank: Unknown
timestamp: March 13, 2016, 03:57:46 pm
content: Quote from: rx8pilot on March 13, 2016, 07:24:46 amFrom the video it looks like a laptop IDE drive.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 13, 2016, 04:18:31 pm
content: If that is indeed true, there are IDE SSD drives. I would be able to trust that instrument so much more with a full image backup. It woule be such a bummer to get it up and running, calibrated only to have the HDD crash rendering it useless.Sent from my horrible mobile....

author: TiN
author_rank: Super Contributor
timestamp: March 13, 2016, 04:19:52 pm
content: It's always an excitement to see that "Signal Path posted a new video" notification pop-up on my phoneWell worth the time watching.One thing I wondered, if it's possible to have basic intro on S-parameters and perhaps some experiments in future with them, to get better idea of practical use of them in high-speed electronics design. Still feeling fuzzy comparing some of the test data with S-parameters. I think it's going to be more and more important topic for today's and future engineers generation as with electronics evolution, with all these USB3, hi-resolution video, faster interfaces speeds we deal with today and such. Connecting two jump wires for 10G differential line on 2-layer PCB will not work anymore, like it was with USB 2.0 years ago...I think Shahriar have lots of experience in this field, which we all can learn.

author: bitseeker
author_rank: Super Contributor
timestamp: March 14, 2016, 06:09:58 am
content: Quote from: AF6LJ on March 13, 2016, 03:57:46 pmIt sounded older, but maybe that's just a sign (and the first thing that caught my ear in the video). Hopefully, it is an IDE or othernormaldrive/interface so it can be readily cloned. The custom OS or whatever that's on there shouldn't matter. Just a straight dd of the whole thing.However, I think Shahriar said he wasn't keeping it.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: March 14, 2016, 04:42:21 pm
content: Thanks for all the comments. I will keep them in mind.I want to replace the HDD, fix the LCD screen with LED backlight and possibly tackle the PLL issue. Maybe make another video out of it.

author: AF6LJ
author_rank: Unknown
timestamp: March 14, 2016, 05:39:10 pm
content: Quote from: Hugoneus on March 14, 2016, 04:42:21 pmThat would be good; looking forward to the video.

author: gslick
author_rank: Frequent Contributor
timestamp: March 14, 2016, 06:50:30 pm
content: We all know that Poochie does the hard work of fixing the issues that stump Shahriar.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 14, 2016, 06:53:25 pm
content: In the meantime, I am studying more on the uses of this instrument.Finally made the decision (at 42 years old) to finish my EE degree and go on to get a masters. Since I spend most of my days learning, I figured I should add some structure and get some credit for the effort.Sharir, you have been a considerable inspiration to do this.

author: Hugoneus
author_rank: Frequent Contributor
timestamp: March 14, 2016, 06:54:43 pm
content: Quote from: gslick on March 14, 2016, 06:50:30 pmThe other day I was working on a broken scope and there was a small connector with a short cable attached to it. When I was trying to close everything up I could not find that cable no matter what. Eventually I gave up and made one from the parts in the lab. Next day when I went to feed Pooch, it was in his food bowl. He keeps taking stuff and putting it in his food bowl!

author: wkb
author_rank: Super Contributor
timestamp: March 14, 2016, 06:55:17 pm
content: Again a very interesting video! Thank you!

author: Hugoneus
author_rank: Frequent Contributor
timestamp: March 14, 2016, 06:57:07 pm
content: Quote from: rx8pilot on March 14, 2016, 06:53:25 pmThank you, I hold this type of compliment in the highest regard. My intention for starting The Signal Path has always been to provide free education and (humbly) some inspiration.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 14, 2016, 07:06:57 pm
content: Quote from: Hugoneus on March 14, 2016, 06:57:07 pmShahriar (spelled correctly this time)I can see you blasting through sophisticated challenges because you have built up the knowledge, skills, and experience to make it seem easy. While I have been able to tackle some big challenges, every step of the process is a learning experience. The end result is that it takes me a long time to get what I want and many times it is just too far out of my intellectual reach to be practical. I really don't like running into my own limitations. Those limitations are considerable since I don't have the foundation - my self-education is full of holes.I may be the only kid in class with an electronics design and manufacturing business. No problem finding lab partners.

author: bitseeker
author_rank: Super Contributor
timestamp: March 15, 2016, 12:41:04 am
content: Quote from: Hugoneus on March 14, 2016, 04:42:21 pmThat's sounds great. Lots of stuff out there that could use similar HDD and LCD fixes.

author: AF6LJ
author_rank: Unknown
timestamp: March 15, 2016, 08:30:24 pm
content: Quote from: Hugoneus on March 14, 2016, 06:54:43 pmMy former Cat Kayles use to do that. She loved to tune around on my amateur radio.I also have a Weller hand piece she has chewed up the outer silicone jacket on.I miss my Cat.Yes that is her in my avatar.

author: TiN
author_rank: Super Contributor
timestamp: March 15, 2016, 11:02:52 pm
content: QuoteHe just contributes his part of help. Instead of looking for stuff everywhere, you will just need to check one place to find needed things!

author: TheSteve
author_rank: Unknown
timestamp: March 15, 2016, 11:21:35 pm
content: Quote from: Hugoneus on March 14, 2016, 06:54:43 pmYou're lucky, my cat puts everything in his water bowl.