Buying an oscilloscope - Page 1
Forum section: electronics / testgear

author: y2khris
author_rank: Contributor
timestamp: June 01, 2016, 09:40:36 pm
content: I am looking to move away from my Rigol DS1102E so I can get an oscilloscope with more channels, additional bandwidth, better math functionality, etc. I have the opportunity to obtain a working Lecroy LC584AL for $450. What do you guys think? Is it a relatively reliable scope? In this day and age, is it a better to stick with the Rigol. Do you think it is a better way to go than a Tektronix TDS 640 or similar?I have already ordered some 500MHz probes, but I am not very experienced so I'd like to read your opinions.

author: nctnico
author_rank: Super Contributor
timestamp: June 01, 2016, 09:45:07 pm
content: Most of the Tektronix TDS600A series don't have peak detect so better stay away from those unless you study the specs carefully and are happy with very short sample memories. Tektronix TDS500 or TDS700 series are a better buy if they are made in 1995 or later (AFAIK no more leaking capacitors in the later models) but still the CRT is a weak point.If you ordered 500MHz high-Z probes (the standard 10M Ohm 1:10) then you have wasted your money because they will load 99.9% of the circuits you encounter too much due to their high input capacitance.

author: y2khris
author_rank: Contributor
timestamp: June 01, 2016, 09:49:27 pm
content: What is your opinion on the Lecroy LC584AL? Is it worth the money or is it completely obsolete?

author: metrologist
author_rank: Super Contributor
timestamp: June 01, 2016, 10:06:44 pm
content: http://www.testequipmenthq.com/datasheets/LECROY-LC584AL-Datasheet.pdf

author: y2khris
author_rank: Contributor
timestamp: June 01, 2016, 10:19:46 pm
content: metrologist: I've read those specs before but I was wondering if they are reliable machines or if the lag horribly when they are being used. I want something that feels snappy, a little bit more like my Agilent 54622D but with expanded capabilities and a color screen.

author: Fungus
author_rank: Super Contributor
timestamp: June 01, 2016, 10:58:50 pm
content: Quote from: y2khris on June 01, 2016, 09:49:27 pmSeems like a very capable beast...Is it in good condition? $450 seemsreallycheap for something with those specs (much too cheap, in fact - a quick google shows most people selling them for $2000+). Do all the knobs work? Is the CRT bright and not too burned-in?If it's all working nicely and you have enough bench space then go for it. If it needs repairs? Think long and hard.Purely as a matter of taste though: It's 20 years old, has a CRT-display, it's huge, it's probably a bit slow (1990s CPU). Some people prefer test gear like that but do you?For that price you could always buy it, try it for a while, sell it if you don't like it. You should get enough money for a new DSO (better than your Rigol DS1102E ... but not with 1GHz bandwidth...)

author: hendorog
author_rank: Super Contributor
timestamp: June 02, 2016, 01:14:40 am
content: Here is a summary on the LC series by Wuerstchenhund - who is a LeCroy guru:https://www.eevblog.com/forum/buysellwanted/huge-test-gear-auction-in-sweden/msg837346/#msg837346

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: June 02, 2016, 08:03:51 am
content: Quote from: y2khris on June 01, 2016, 09:49:27 pmIf it is in good and fully working condition then it's more than worth the money.QuoteIt simply comes down what you want, really. The HP/Agilent 54600 scopes are very basic scopes that were designed for a very high waveform update rate to replace analog scopes as general purpose scope. If you're using a digital scope pretty much like an analog scope (i.e. staring at the screen to find glitches) then the 54600 Series is hard to beat.The LeCroy LC Series scopes however are advanced high end scopes which are more like waveform analyzers. They offer a wast range of measurements, math and analysis functions that especially back then when the LC was current was pretty unique (neither Tek nor HP could offer anything close back then), and even today most of these functions can still only be found in more advanced scopes. Signal issues aren't found by staring at the screen but by setting up appropriate triggers (which there are many), or using some of the advanced analysis tools (i.e. jitter/timing analysis, power measurements) that are available in the scope.If by "feeling snappy" however you mean that the user interface reacts without "lagginess", then there's no need to worry. Also, the LC Series, like all these older LeCroy scopes, use a very simple menu system which is somewhat different from other scopes but in general is very easy to operate once you're familiar with it.Quote from: Fungus on June 01, 2016, 10:58:50 pmThat might be what some people are asking, but no LC Series scope is worth anything close to $2k (which already buys you some of the later models, i.e. the WR2LT or the WavePro 900).QuoteIt's quite big (like pretty much any high end scope) but it's not slow. The CPU (a 96MHz PowerPC) is actually pretty fast, and the lean OS (a proprietary OS developed by LeCroy) helps, too. It offers update rates up to 33k wfms/s (in sequence mode), fast deep memory FFT (IIRC up to 1M, which was huge back then), analog and color persistence mode with 16bit/pixel (64k levels of brightness), ERES up to 11bit vertical resolution, and so on.The only thing its lacking is a network port, but it comes with GPIB as standard.Of course, it's still almost 20yrs old, and due to age alone there's always a chance something could fail, but at least schematics are available.

author: nctnico
author_rank: Super Contributor
timestamp: June 02, 2016, 11:32:53 am
content: I'd get the Lecroy LC584AL! For $450 it offers good value for money even if it needs some TLC.

author: y2khris
author_rank: Contributor
timestamp: June 02, 2016, 12:10:48 pm
content: Thank you all so much for your valuable input. I am certainly leaning more towards getting it; you are a persuasive bunch.Wuerstchenhund: you are a scope god! So, since I have the Agilent scope, should I stop looking for a Tektronix 2467 to replace the GOS-630FC? I take it that once I have the Lecroy, the Rigol DS1102E will be useless to me as well. (Downsizing to 2 scopes will be nice if I am not sacrificing too many capabilities.)In addition to the power on self test and checking for the 1KHz square wave on every channel, is there anything else I can do to verify the proper function of the scope? Are there any self test failures that I should disregard? In Dave's spirit, I will take it apart; other than dusting it out, checking electrolytic caps for bulging or seepage, changing out the temp sensors, and disabling the printer, is there anything else I should be doing to keep this scope going for the foreseeable future? It seems that on Tektronix scopes the ICs fail quite often; are these Lecroys plagued by the same issues?I am very glad you mentioned the FFTs as both the Agilent and Rigol left something to be desired in that department. Checking my Agilent function generator output gave me very unexpected results and made me not trust either scopes FFT capabilities as they didn't match up very well either.I just picked up a stable 10MHz source. Is there anyway to input that source as the "calibration" signal so I can make sure it is measuring frequency accurately?

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: June 02, 2016, 02:32:43 pm
content: Quote from: y2khris on June 02, 2016, 12:10:48 pmNo, not really. Just happen to know these modelsQuoteYes, just don't. There's no point in investing money in obsolete antiques like those analog boat anchors.QuoteThat depends on what you want to do. Capability-wise the LC can do everything the DS1102E can (and more). However, the DS1102E is portable, and if you need portability then I'd consider keeping it.QuoteChecking each channel with the calibration square wave at the highest setting (IIRC you can change the frequency up to 1MHz) is a start. Step through the whole vertical range for each channel and look for signal deformations or amplitude issues.Also, test every button and knob on the scope, and make sure the encoders work without dropouts/jumping.Check the CRT for burn-in, and for convergence issues (alignment of the red, green and blue traces), especially in the corners. It's easier when you set the graticule to fullscreen.Make sure the fan works and doesn't make any worrying noises.Last but not least, go to the config page and check what options are installed, and check the aquisition memory displayed is 8M.QuoteNo. If there is an error then there's a problem.QuoteThese LeCroy scopes don't suffer from the capacitor plague or dying ICs, but of course that's not to say that due to the age there can't be any defective caps. Also check heat sinks for being mounted properly (not loose).What you should do is to check the service note for the auto-voltage circuitry (note can be found in the Yahoo LeCroy group) and perform the steps listed there to disable auto-voltage. Also, check the temperature sensor on the large PSU heatsink, if they get old they sometimes get brittle and come loose.But that's pretty much it.QuoteRigol's FFT is a joke due to it's low number of used sample points, pretty much on all scopes except the DS1054z with the latest firmware (where they upgraded FFT to 16kpts which is now only 'poor' instead of 'useless').FFT on the 54600 Series was pretty much an afterthought (the older HP ones needed an extra hardware module for that), and while the UI is better than on the Rigols it's still a very limited low memory FFT.QuoteIf I remember right some of the LC Series scopes had a ref clock input on the rear (which I think was a hardware option), which should be useable to lock it to your 10MHz reference if your scope has it.

author: y2khris
author_rank: Contributor
timestamp: June 03, 2016, 02:46:57 am
content: So, I just picked it up a few hours ago. All of the encoder knobs are missing and the top encoder from the "System Setup" section is kind of wonky but other than that, this thing does seem spot on. When I picked it up, it's scale didn't hit me till I tried to set it up on my work bench; this thing is HUGE! I have been using it for the past hour and the interface will take some getting used to, but I have to say, it is more optioned out than I could have imagined; it really seems like a professional piece of kit.

author: y2khris
author_rank: Contributor
timestamp: June 03, 2016, 02:50:40 am
content: Just a few minutes ago while I was doing some FFTs on a few channels and pushing the scope pretty hard, it started rebooting with increased frequency, so I turned it off. Have you heard of this occurring?I have not taken it apart yet because it is a very intimidating machine but I am guessing it has something to do with that thermal sensor or the power supply.

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: June 03, 2016, 05:19:58 am
content: Quote from: y2khris on June 03, 2016, 02:46:57 amThat's not good, I hope you asked for a price reduction?QuoteYes, these scopes are big. I have the successor of the successor of the successor of your scope (WavePro 7300A), which is around the same size, and it takes up a lot of space. But then, it comes with a large display, which compensates somewhat for its bulkiness.QuoteThe UI takes a bit getting used to. One thing to remember is that LeCroy originally comes from the high energy physics corner, not the EE sector as other scope manufacturers, and that shows in their scopes. For example, one of their philosophies is that a scope must show the original waveform unaltered unless the user explicitly enables a function that does so. That means that where manufacturers like Keysight and Rigol apply stuff like interpolation automatically based on timebase settings, on a LeCroy you have to explicitly enable it.I'd strongly recommend to have a look at the LC operating manual and especially the color oscilloscope hands-on guide:http://cdn.teledynelecroy.com/files/manuals/lc_om_reva.pdfhttp://cdn.teledynelecroy.com/files/manuals/lc_hg_revc.pdfQuoteNo, and that definitely should not happen (the scope should not reboot no matter what you do), and it suggests that there is a hardware problem. It could be wonky contact between the boards, or a RAM problem, which thankfully is standard old-style PC type memory (if I remember right it's FPM/EDO, either in PS/2 SIMM format or DIMM format) so replacement isn't difficult.QuoteNo, that sensor would have caused a shutdown, not a reboot.The fact that it seems to reboot when you're doing something more demanding hints to either a memory problem (which as I said is easy to fix) or a real hardware problem (which will be more difficult to sort out).I'd start with cleaning and reseating the boards. If that doesn't help then I'd look at the memory. The LC584AL should have 64MB in the form of two 32MB SIMMs or DIMMs, I'd remove one and try again, and if it still reboots then try with the other one. If the scope reboots with each of the modules then there's something else causing the reboot.BTW, once you fixed the reboot issue and you're sure the scope runs stable, make sure to upgrade the firmware to the latest version (9.3.0) which can be done through a Windows PC connected via GPIB or serial port and the software ScopeExplorer:http://teledynelecroy.com/support/softwaredownload/scopeexplorer.aspxScopeExplorer tries to download the correct firmware files automatically, but if it fails then you should be able to find the last firmware files in the Yahoo LeCCroy group.

author: Fungus
author_rank: Super Contributor
timestamp: June 03, 2016, 08:47:51 am
content: Quote from: y2khris on June 03, 2016, 02:46:57 amGood change to ask for a discount.Quote from: y2khris on June 03, 2016, 02:46:57 amI told you so.(and compared to a DS1104E it's probably quite a shock...)Quote from: y2khris on June 03, 2016, 02:50:40 amOh, dear.Quote from: y2khris on June 03, 2016, 02:50:40 amIf you're prepared to have a go then it can probably be fixed. The fact that it works well for 40 minutes seems to indicate the main chips are OK. The CRT was a big worry, too, but that seems to be working.

author: y2khris
author_rank: Contributor
timestamp: June 03, 2016, 08:50:49 am
content: Wuerstchenhund, thanks for all of your expert guidance!QuoteI didn't get one because it was already so cheap. I used some contact cleaner on each of the encoders and now they all seem to work pretty well, so now I am on the hunt for D-Shaft knobs. I measured them with some calipers and they are indeed 1/4 inch, 6mm.eBay auction: #http://www.ebay.com/itm/20-x-Plastic-Control-Knob-Insert-Type-12mmDx19mmH-6mm-D-Shaft-Red-or-White-/251886417104?hash=item3aa599b4d0:g:ugIAAOSwv0tVC7caQuoteI think that I will actually prefer this kind of setup in the end. Using it side by side with the Agilent, this is a bit of a dog, but I really love its capabilities.I went ahead, took it apart, re-seated the RAM, disconnected the printer and put it back together. When it started rebooting, it had run for about an hour or more, so I think it might have something to do with heat. If it reboots again, I will have to dig into the complicated oscilloscope and reseat all of the boards as you have suggested.QuoteThat's great because my scope is running 8.9.0, but yes, I will make sure that my scope is VERY, VERY stable first.Is there any reason to change the CMOS batteries on these? I noticed that it is soldered on and claims to be rechargable.I really love the zooming capabilities of the oscilloscope! One weird thing about the FFTs is that they all have the flat bottom. As suggested, I am working through the hands on guide and it is lots of fun!

author: Jwalling
author_rank: Unknown
timestamp: June 03, 2016, 10:16:09 am
content: Quote from: y2khris on June 03, 2016, 02:50:40 amIIRC, that scope uses a connector similar to the ATX power connector on a standard PC. I've seen this series of scopes develop contact resistance at this where the two connectors meet. This generates heat and the problem spirals out of control to the point where the connector housing starts to melt or burn. The voltage drops across the contacts is enough to cause the re-boots. Take a look at the connectors and look for a discoloration (usually a yellowish brown) in the plastic housings ASAP before it gets worse! They should be nice and white. Good luck!Jay

author: Wuerstchenhund
author_rank: Super Contributor
timestamp: June 03, 2016, 11:00:19 am
content: Quote from: y2khris on June 03, 2016, 08:50:49 amThat's what we are here forQuoteDon't forget that you can save the scope setup to a setup file, which makes it easy to have pre-set profiles for every circumstance. These setup files, as well as screen shots in BMP format, are saved on the optional "hard drive" (used to be an IBM MicroDrive or a PCMCIA flash card, but if you have the HD01 option then a CF card in a PCMCIA-to-CF adapter will do fine, although the file system limit is 512MB FAT12 so larger cards are a waste).QuoteI also have to second what Jwalling said, check these ATX-style power connectors.QuoteYes, it's rechargeable, but after 18 years it's probably near the end of its life. A replacement is a good idea as if the voltage drope then the scope will refuse to complete booting.QuoteYes, zooming is great on these scopes. You can not only do a zoom of the original waveform, but also of an FFT spectrum, a math function or pretty much any trace, even a math function.BTW, what options does your scope have?QuoteThat's probably because of the settings you use. Check your FFT Results mode (it can do Imaginary, Magnitude, Phase, Power Density, Power Spectrum, Real and Real+Img; for standard FFT you'd want Power Spectrum).QuoteGood! That's the best way to learn how to operate such a complex instrument

author: Fungus
author_rank: Super Contributor
timestamp: June 03, 2016, 11:10:13 am
content: Quote from: y2khris on June 03, 2016, 08:50:49 amOK, we'll place you inthatgroup then.PS: How much did you say you were selling the DS1102E for...?

author: y2khris
author_rank: Contributor
timestamp: June 03, 2016, 09:52:16 pm
content: Thanks again for all your help!So I ran it 8 hours straight with all four channels on and all math/zoom channels doing stuff too and it didn't reboot. I then made sure to re-seat the board with the RAM on it into the larger board, I re-seated all the connectors that could be reached and I put it back together. I tried to take the bottom cover off, but something was holding it and I am apprehensive about taking the entire thing apart unless I really, really have to. After all that, I just tested the noise on my power supply (1V 0.000A draw) and it restarted again for some reason; I let it reboot and added additional traces and it hasn't restarted in 45 minutes. I am used to relays clicking a lot, but this one likes to randomly click relays sometimes when I am not changing settings. Is this normal with Lecroys?Is there a service manual for the LC series?QuoteI didn't even know they made PCMCIA cards that took housed SD cards, once I get this thing figured out, I will go that route.Regarding what you guys were saying about the ATX style connectors, are they on the bottom section where the BNC connectors are? I wasn't able to get the bottom cover off, but I found some old connectors that resembled old AT connectors and those looked absolutely fine and white as Jwalling had suggested.The CMOS battery is 2.644V, so it will be changed out soon. Should I use a standard lithium battery or are rechargeable batteries (like the one that it has now) a better fit?QuoteSoft Options: WP01, WP02, WP03, CKIO (The CKIO isn't enabled by the software key)Hard Options: CPUP VGAC, GPIB, R232, CLBZ, FD01, CENT, I2CMain Processor RAM size: 64M bytesAcquisition Memory Size 2M (my the way, it did allow me to use all 8MB on one channel when I was testing it, actually using all that memory is a different thing entirely)QuoteI've played with all those settings but to no avail.On a happy note, I love the measurement and statistics capabilities!

author: tautech
author_rank: Super Contributor
timestamp: June 03, 2016, 10:02:07 pm
content: Quote from: y2khris on June 03, 2016, 09:52:16 pmMost likely it's auto Self Cal.QuoteCapturing a fast waveform at a slow timebase setting and zooming in is when memory depth is needed.

author: y2khris
author_rank: Contributor
timestamp: June 03, 2016, 10:09:06 pm
content: Darn, now that I've sent the message, it just decided to crash on me.I had one probe plugged into its calibration port on channel 1 and on channel 2 I had it plugged into my function generator running at 1MHz, I was adjusting the trigger level and it just rebooted again. I unplugged the probes and it continued to crash. I let it sit for a few minutes and it is currently on with no probes connected.Why would it run so long till it crashed randomly? Could it be something with the power supply heating up? Does the scope maintain a non-volatile error log? I checked the error log under Utilities-->Special Modes-->Remote Ctrl. Assistant, and that is the only log I can find.QuoteIs it best to disable it? Could that possibly have anything to do with the crashing?

author: nctnico
author_rank: Super Contributor
timestamp: June 03, 2016, 10:13:23 pm
content: It seems the crash is heat related. The first thing to look for are electrolytic capacitors in the power supply but freeze spray is required to pinpoint the part of the circuit which causes the crash.

author: y2khris
author_rank: Contributor
timestamp: June 04, 2016, 12:42:58 am
content: I have a feeling that I will be taking this thing apart a few more times before it is fixed. When it is working, I love it though.QuoteI apologize for my newbishness but what would I do with freeze spray?

author: MT
author_rank: Super Contributor
timestamp: June 04, 2016, 12:55:43 am
content: To drastically change the temperature of a component to see if its damaged..all components have temp range in which they shall work up to specification. You can have some issues with the power supply, or some of the DRAM's is out of order if it reboots randomly.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 06, 2018, 09:21:22 pm
content: Quote from: Wuerstchenhund on June 02, 2016, 02:32:43 pmThis thread is 8 months old but since I'm working on an LC scope I'll throw in what I know.The Ref Clock input part of the CKIO option. If you scope has it then there will be three BNC connectors on the back near the bottom of the panel. I think that option can be turned on with the Option GAL but it also includes three short cables that plug into plugs on the main board and have the BNC jack on the other end. I don't know if there's anything else needed. You can see drawings of it in the LC 564 service manual which is posted online.