EEVblog #217 - Lecroy 9384C Oscilloscope Teardown - Page 1
Forum section: electronics / general

author: PeterG
author_rank: Frequent Contributor
timestamp: November 18, 2011, 09:39:27 am
content: YouTube is saying it has been removed?Did Dave remove it or is YouTube on the fritz?Regards

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: November 18, 2011, 09:52:20 am
content: Working link here :

author: EEVblog
author_rank: Unknown
timestamp: November 18, 2011, 10:04:45 am
content: Quote from: PeterG on November 18, 2011, 09:39:27 amBoth.Youtube screwed the original upload. It turned out 4:3 with a corrupted start.Deleting and re-uploading fixed the problem.Also, I learned the hard way that Youtube does not allow you to upload the same video twice (it does a checkum), so you can't leave the old one up until the new one uploads, you have to delete first.Dave.

author: Unknown
author_rank: Unknown
timestamp: November 18, 2011, 10:24:52 am
content: How about a small competition?Who can guess correctly what the problem is before #218 is uploaded?The winner gets special recognition for remotely diagnosing LeCroy 9384C Oscilloscopes.Also my special bonus "Pi to the precision of the Feynman Point" for free.

author: phil_jp1
author_rank: Regular Contributor
timestamp: November 18, 2011, 11:37:20 am
content: Quote from: HAL-42b on November 18, 2011, 10:24:52 amMy guess is video #218 would be not about LeCroy scope repair.

author: EEVblog
author_rank: Unknown
timestamp: November 18, 2011, 11:50:52 am
content: Quote from: phil_jp1 on November 18, 2011, 11:37:20 amYou are likely correct!I have the service manual now, but it takes time to debug digest it and debug these things.If anyone knows what #218 will be, please let me know, because I have no idea!Well, actually, I do have 3 videos to edit from the HAM radio meeting I went to the other night. I don't really like giving those types of videos a blog number, but I guess it doesn't really matter and help identify them?Dave.

author: Unknown
author_rank: Unknown
timestamp: November 18, 2011, 11:59:50 am
content: Quote from: EEVblog on November 18, 2011, 11:50:52 amEngineers for ya

author: samgab
author_rank: Frequent Contributor
timestamp: November 18, 2011, 12:51:43 pm
content: Quote from: EEVblog on November 18, 2011, 11:50:52 amExcluding the ham radio stuff, maybe 218 can be your solution to the Agilent upload problem and analysis of the second 1000 resistors?

author: lindworm
author_rank: Contributor
timestamp: November 18, 2011, 01:19:50 pm
content: Seems like 217 isn't in the actual blog but on youtube only?

author: McMonster
author_rank: Frequent Contributor
timestamp: November 18, 2011, 01:30:52 pm
content: Sometimes there's a delay of up to a day between video appearing on Youtube and eevblog.com.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: November 18, 2011, 01:39:27 pm
content: Quote from: HAL-42b on November 18, 2011, 10:24:52 amAfter watching the video my first best guess would be corrupt display ram. The Dacs (4 off) all appear to be working as normal and the corruption is Static in the waveform and consistent across channels. This would indicate a common link, either power supply or display? More twiddleing would be required but a possible test would be to zoom into the wave form and see if the corruption stayed in the same place (on the screen) or panned with data stream. This may help point to the problem. Check the memory stick is seated/ clean seen similar problems on video cards in a pc before.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: November 18, 2011, 03:30:59 pm
content: Quote from: FreeThinker on November 18, 2011, 01:39:27 pmLooks that we are playing the wild guess game.In this case I would re-flow the display CPU, memory issues are permanently and cause digital garbage on the screen.Some hot air on the display CPU pins would show if it is responsible or not, before actually trying to re-flow it.

author: firewalker
author_rank: Super Contributor
timestamp: November 18, 2011, 03:47:33 pm
content: Dave, does this scope use a standard "tv" CRT (easy obtainable)? Ghost images annoy me very much! I had an old monitor with windows 3.1 logo burned...Alexander.

author: david77
author_rank: Frequent Contributor
timestamp: November 18, 2011, 04:22:04 pm
content: One can safely assume it's not a standard TV tube. The amber colour gives it away, it is a tube more like they were used in old monochrome computer monitors back in the 80's.

author: nixxon
author_rank: Frequent Contributor
timestamp: November 18, 2011, 06:49:49 pm
content: Next time the scope is powered up it will probably work flawlessly. Dis- and reassembly have fixed stuff before...

author: FreeThinker
author_rank: Frequent Contributor
timestamp: November 18, 2011, 07:34:17 pm
content: Quote from: Kiriakos-GR on November 18, 2011, 03:30:59 pmNice to see you post a sensible comment.Acquisition seems to be ok, triggering ok, time base ok. This would leave power supply problems, display, and vert amps. Looks likely that the vert amp or associated circuitry needs a look at. This however doesn't explain the display corruption and my suggestion of checking the ram chip is a quick and easy test, (provided of course that it holds the vid output) based on experience and available facts. To suggest reflowing the board is a reach to far given the Facts.

author: phil_jp1
author_rank: Regular Contributor
timestamp: November 18, 2011, 07:36:35 pm
content: Quote from: FreeThinker on November 18, 2011, 01:39:27 pmI don't think that there's any problem with corrupted display ram or display board at all. It's because vertical scale was all over the shop. It was outputting right input signal shape, but with the completely wrong vertical scale.As Dave said, first of all the power supply output should be checked. It was 12 years in(presumably daily) operation. Even if caps looks ok, they can have a very substantial ESR.Quote from: nixxon on November 18, 2011, 06:49:49 pmYeah!

author: McMonster
author_rank: Frequent Contributor
timestamp: November 18, 2011, 07:50:44 pm
content: Quote from: phil_jp1 on November 18, 2011, 07:36:35 pmBut beware of the Leftover Screws Axiom!Quote from: Leftover Screws AxiomGiven finitely large number of cycles of the above algorithm you run into danger of being killed by excess of screws filling your lab as given from the axiom.There's also a positive side effect of possibility to research a new free energy source by deriving the axiom and turning the screws into energy using the famous E=mc^2 equation.

author: tesla500
author_rank: Regular Contributor
timestamp: November 18, 2011, 09:09:53 pm
content: The dangling cable coming out of the power supply is probably for the internal printer option.I wonder if the maximum sample memory is only available at lower sample rates. The RAM cards have 192 pin connectors, so the data bus on each card is probably 128 bit. The ram chips are rated at 66.6MHz, giving only about 1GB/sec bandwidth to each card for 2GB/sec total. Running all 4 channels at 1GSa/sec requires 4GB/sec.

author: don.r
author_rank: Frequent Contributor
timestamp: November 19, 2011, 02:14:31 am
content: Quote from: nixxon on November 18, 2011, 06:49:49 pmYeah. Quite common on Tek scopes with the connectors.I love the Sagan background "soundtrack" on the video, btw. I haven't heard crying like that since I dinged my new car at a car-park.Definitely looks like a memory reading problem with all those glitches and then the time base being screwy right at the same point. Maybe some of those push-pin connectors were loose.Finally, hearing the 68030 being called "old school" makes me feel like a grand-dad!

author: BubbaMc
author_rank: Contributor
timestamp: November 19, 2011, 04:42:50 pm
content: Quote from: nixxon on November 18, 2011, 06:49:49 pmAnd have broken stuff

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: November 20, 2011, 04:22:57 am
content: Im interested howmany $ did this scope set you back Dave?

author: scopeman
author_rank: Frequent Contributor
timestamp: November 21, 2011, 04:19:56 am
content: Hello Dave,As an introduction, I am the moderator and owner of the independent LeCroy_Owners_Group on Yahoo! Groups. You can find a lot of information on the group site as well as overflow manual and firmware files,etc. onwww.ko4bb.comin the LeCroy Manuals section.I can tell that you like poking fun at the circuitry and design as you go through things but remember in 1999 no manufacturer had an equal to these scopes in terms of sample rate, memory depth and math measurement capabilities. If you add in all of the possible options the deep memory (2Mpt/channel simultaneous 1Gs) version of this scope went for something like 40K, maybe more. I have several LeCroy scopes from this era that I still use on a regular basis and a more modern 104MXi that I use almost daily.It took years for HP and Agilent to finally begin to understand that deep memory is important in a digital scope, and in some cases I still don't think they get it. And how you manage that memory is even more important. LeCroy currently makes some of the real "killer" scopes on the market today. Their new 12bit one is a must see.Maybe you should contact your local LeCroy office and see if they would agree to have you review one of the more modern ones. The math and performance is outstanding. I think their fastest scope is 45GHz at 100+GHz sample rate!To address some things in your video.Originally this series of scopes was manufactured in the LeCroy plant in Switzerland (93XX and 93XXA). The C model was manufactured in Chestnut Ridge NY as all of the high line series (making LeCroy the only remaining U.S. manufacturer of oscilloscopes.These scopes were never really intended to be serviced in the field like a Tek 475A. The units were calibrated and verified by specialized calibration and troubleshooting equipment developed by LeCroy. This is not to say that you can't fix the scope, indeed I have repaired many but there are certain things that make the repair difficult.For one thing there are many, as you have noted, custom IC's that LeCroy designed that are simply not available on the open market or from LeCroy since the units are long out of production. Specifications for the parts are also unobtainium. As you also noted there are many GALS in the scope that are of course protected so replacing those would be difficult as well. I would recommend finding a similar one one ebay for spare parts.One particular problem with the 9384A/C is that the input in the 50 ohm mode is susceptible to ESD damage from a charged 50 ohm cable. This is a common fault. The HEF series part was a custom and the only fix is to find another scope that you can use for parts. I currently have a 93X4C scope that I junked because it had three wrecked inputs.As for your scope problem since it is common to all channels I would suspect a data bus problem, maybe even system ram. There are 72pin SIMMS on the CPU3 MC68EC030 card that you can swap to see if the problem goes away but I don't think the ADC cal errors are caused by that but swapping them is easy. There is a note that I wrote up on the group site about the memory. Maybe just reseating the CPU card may work as these get jostled in shipping.As an aid to trouble shooting there is a maintenance mode that you can enter from the from panel with the scope stopped. See the attached excel file for hints.Also don't forget that we have a fairly large base of users on the group so feel free to join and post your problems there. Many of the group members have experience fixing these scopes.While you have the unit apart I would also recommend that you measure and scope the power supplies.I believe that the Coax you see is for distributing timing to various places so that the sampling is truly synchronous. One of the features if these scope is the ability to combine 2+2 channels to double the sampling rate and the memory depth. By using an external PP adapter you can double that again (but you are restricted to 50 ohm measurements with the adapter).Fortunately I have not had to work on the main acquisition board on these scopes except to fix an input relay (sometime a rap with a pencil will un-stick them) orto make a rare calibration adjustment. If these scopes are not abused they will hole their calibration for years. Usually all that is needed is to occasionally blow out the dust and every 5 years or so replace the rechargeable lithium battery on the CPU card. There is a note on the site on the battery replacement as well.Take care and good luck and let me know how you make out.Sam Reaves(Scopeman)P.S. I do not work for LeCroy or have any official affiliation, I just like their stuff!P.P.S - The real LeCroy scopes are the ones that are above the entry level WaveAce and WaveJet models.P.P.P.S -- You need to add rar as one your acceptable file upload types!

author: amspire
author_rank: Super Contributor
timestamp: November 21, 2011, 06:32:03 am
content: Sam,Nice website! Lots of great pages there and thanks for the manuals sections. I like the GPIB stuff as I have to get some GPIB working at home somehow.The HP1740A manual is that lousy version floating around with no schematics. Arghhh!Do you want a copy of the service manual with the schematics - I can upload it, if you like.Richard

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: November 21, 2011, 11:03:19 am
content: Lets keep the discussion about this great scope Dave has gotten then instead various personal wars

author: EEVblog
author_rank: Unknown
timestamp: November 21, 2011, 11:07:17 am
content: Awesome, thanks for the info Sam, much appreciated!Dave.

author: ivan747
author_rank: Super Contributor
timestamp: November 22, 2011, 12:12:15 am
content: Quote from: scopeman on November 21, 2011, 04:19:56 amI didn't know there were oscilloscope brand fans! You really know what you are doing.Wow, they don't even do anything with a bandwidth lower than 40MHz!RAR is proprietary and not as widely accepted as ZIP.Thanks for your advise, now I am no longer disappointed for not seeing a solution to the problem the scope has, and we get a new video!

author: colinbeeforth
author_rank: Contributor
timestamp: November 26, 2011, 02:33:17 pm
content: Dave, entertaining and interesting video as usual. My fingers are crossed for you with this one. Sam's advice will help. I've done some 93XX repairs, so there are a few LeCroy owners in Oz. I've had a LeCroy 9310M for 9 years now. With WP01 and WP02 waveform processing options, it is a complete design lab in itself. Despite its age, it is the most useful and capable piece of test gear I own.I recently thought I'd try one of the low cost modern DSOs. I did a ton of research and bought a Hantek DSO5102B for 630 bucks. It was the only low cost DSO with a display of 800 horizontal by 480 vertical - think about 8 bit vertical digitising (256 levels) most cheap scope screens only have QVGA or 240 vertical pixels available. It's no wonder they show jaggy looking sine waves. The display always suffers from vertical alias since it can't show 256 levels in 240 pixels. The Hantek is one of the few cheaper DSOs that also has a proper acquired_memory_to_display_compression_algorithm. Think about how to display 40k of data onto only 800 horizontal pixels... Most DSOs simply decimate that data and show only a tiny percentage, 40k/800 = 1 point in every 50! The other 49 are not shown. Decimation totally destroys the ability of the screen to show narrow features, like a pulse. The Hantek colour screen is nice. Screen=good, everything_else=sucks. I thought ten years of development might have improved the lower cost designs. The digitisers are noticeably noisy, the software is average and buggy, and you simply can't replace the raw horsepower of the LeCroy hardware with software, it just doesn't compare. The 9310 has a lot of ECL chips inside. Frankly, considering the low cost, the Hantek is useful, but by comparison, the Hantek is a tricycle and the LeCroy is a Ferrari. There are no seat belts, no hands held, you gotta read the book, and work those knobs, but it performs superbly and gives you so much. I've used a 9310 to measure video pre-emphasis in a video signal going into an FM modulator loop at only 2 millivolts peak to peak. You can't even see that signal with a cheap scope let alone measure it. I've used a 9310 to find a millivolt magentic resonance signal amongst 20 volts of RF interference! The LeCroy is like a surgical knife where other scopes are just hammers. No-one expects to drive a Ferrari with no training, or to perform surgery without learning how to do it. DSOs require some reading and time learning to drive them. I get a bit annoyed when people complain that LeCroy are "hard to drive". My answer is, so is a Ferrari, if you want easy, here's a billy cart...Ivan747 said "I didn't know there were oscilloscope brand fans!" I guess there is. I'm not a one-eyed fanboy. It's based on years of experience using different DSOs and seeing the results. The modern up market HPs seem to have caught up with LeCroy, and there are other makers that look ok, but I have no personal experience with DSOs like Rhode and Schwarz, Hameg, Iwatsu and Yokogawa. In terms of bang for buck, the older LeCroys are amazing, despite the obvious issues of keeping such older gear running.Good luck mate, Colin

author: colinbeeforth
author_rank: Contributor
timestamp: November 26, 2011, 03:19:48 pm
content: FirewalkerHi Alexander,I've seen new LeCroy 93XX series CRTs available on eBay fairly regularly. It's a plain TV type CRT, electromagnetically deflected, with a monochrome orange phosphur. It seems to burn fairly easily as many older 93XX series scopes have obvious screen burn when they are turned off. Interestingly, LeCroy did have an anti-screen-burn feature that caused the display to move around in a small circle over time. It was only a few pixels worth of movement, but you can occasionally see it jump if you watch for a while. Obviously it wasn't enough to prevent screen burn. Unless it is fairly bad though, it's hard to see when the scope is on, so don't refuse to buy one because some burn is visible when the scope isn't on.LeCroy changed from totally vector graphics on the earlier 94XX series scopes, which was brilliant, to a more common raster scanning type screen system on the 93XX scopes. At the time I remember worrying that they wouldn't look a patch on the nice vector displays. In the end, the scanned screens weren't quite as nice as the vector screen, but they didn't suffer from repaint speed problems when you displayed a lot of waveforms. This was quite improtant for the 4 channel scopes, or when you are using waveform maths and showing 4 waveforms on the screen. Curiously, the screen raster scan is 90 degrees rotated compared to a TV. The lines scan vertically and the much slower 60Hz frame scan is horizontal. That means there are 810 vertical lines scanned, with 696 pixels per line. That makes the effective pixel count 810 horizontal by 696 vertical. Not all that high, but in practice, you can show two separate waveforms each with it's own grid and map the 8 bit (256 level) vertical resolution onto available screen pixels without creating any screen alias. In practice, you can't see any pixels, so the display looks nice and every bit as good as an analogue scope. You can also split the sreen into 4 sets of grids and show one waveform for each grid. With the earlier 9310s for example this was all done with a 68020 processor, which also handled all the other housekeeping, scanned the front panel knobs and ran the scope. The software was very impressive. The software team at LeCroy worked in Switzerland and ported over the 94XX software, adding improvements and the raster scan system for the 93XX on only 3 weeks. I used 9310 serial number 013 for 6 months flat out and never saw one software bug. It was a pretty impressive achievement I think.If you see an older LeCroy being advertised, get the seller to press the "Show Status" front panel button. Then select the option "System" from the soft buttons. You get a display of: 1. Serial Number 2. Software Revision 3. Software Options 4. Hardware Options. The software options can include WP01 - Waveform Maths and WP02 - FFT. The software options cost the original buyer several thousand bucks each, and are worth looking out for.The attached brochure sets out the various models and options for scopes that are on the second hand market now.Cheers, Colin

author: vaualbus
author_rank: Frequent Contributor
timestamp: December 05, 2012, 10:58:53 am
content: I Dave I want to have a information where you get the service manual of the oscilloscope?I need them for repair mine and I can't find that on iternet.If you can send me the link were you find it I will be vary happy.Alberto.

author: scopeman
author_rank: Frequent Contributor
timestamp: December 06, 2012, 04:53:20 am
content: Alberto,Please look up my LeCroy_Owners_Group on Yahoo! Groups and also the LeCroy section of thewww.ko4bb.site.I believe that you find what you need. You can join the group for free.Best regards and good luck with your scope.Samhttp://tech.groups.yahoo.com/group/LeCroy_Owners_Group/?yguid=406654882http://www.ko4bb.com/manuals/index.php?dir=LeCroy