EEVblog #217 - Lecroy 9384C Oscilloscope Teardown

[EEVblog]

Awesome, thanks for the info Sam, much appreciated!

Dave.

[ivan747]

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!

I 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!

[colinbeeforth]

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

[colinbeeforth]

Firewalker

Hi 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

[vaualbus]

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.

[scopeman]

Alberto,

Please look up my LeCroy_Owners_Group on Yahoo! Groups and also the LeCroy section of the
www.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.

Sam

http://tech.groups.yahoo.com/group/LeCroy_Owners_Group/?yguid=406654882
http://www.ko4bb.com/manuals/index.php?dir=LeCroy