Need help to choose between Lecroy LC574AM and Tektronix TDS754A  - Page 1
Forum section: electronics / testgear

author: analogRF
author_rank: Super Contributor
timestamp: September 28, 2017, 01:53:44 am
content: I have a limited time window to buy either LC574AM or TDS754A for a relatively good price. They are both in pretty good shape aesthetically and functionally.754A comes with two P6139A probes but the Lecroy has no probes. I know one is 1GHz and the other is 500MHz but it is equally acceptable for me and I am limited by the bandwidth of probes anyways (I can only afford to buy 500MHz probes for the lecroy and not those expensive ones). So the BW is not the deciding factor here.Lecroy is about C$200 cheaper which is probably just about the cost of the probes.I have never worked with any of these two and never seen any other Lecroy scope before. 754A has option 1M so it has 500K memory length.Now I have seen bad and good stories about both. Could someone with firsthand knowledge about both scopes help me out here?In terms of functionality, accuracy, update rate, their look and feel and user friendliness, etc etc...can someone help?Is the 4GS/s (on single ch and 2Gs/s on 2 ch) and 1GHz BW on Lecroy really true or there is a catch into it.Any information or past experience is greatly appreciated.

author: swingbyte1
author_rank: Contributor
timestamp: September 28, 2017, 02:15:01 am
content: Hi. I have a lecroy and it is good. The extra bandwidth is still usable with direct connection to the circuit so I wouldn't be discounting it due to lack of probes. The 2GS 2ch mode is available from the front panel but the single ch 4GS mode requires a channel combiner unit. The signal processing and trigger systems are very good and I now prefer the lecroy way to the other ways.Sent from my Nexus 5 using Tapatalk

author: analogRF
author_rank: Super Contributor
timestamp: September 28, 2017, 03:34:24 am
content: How is the waveform update on Lecroy?754A claims to capture 400000 waveform/sec with instavu

author: nctnico
author_rank: Super Contributor
timestamp: September 28, 2017, 06:01:52 am
content: Forget about Instavu. It takes 20 to 30 seconds to get into that mode and beyond that it is very limited. IMHO the LC574AM is a much more capable scope and you can liberate all the options by adding a GAL.

author: eKretz
author_rank: Frequent Contributor
timestamp: September 28, 2017, 08:41:43 am
content: Mmm, I have a 754A and it doesn't take anywhere near 20-30 seconds to activate InstaVu. More like 5 seconds. Admittedly still seems a bit clunky compared to the later D models though.

author: analogRF
author_rank: Super Contributor
timestamp: September 28, 2017, 11:38:49 am
content: Quote from: nctnico on September 28, 2017, 06:01:52 amsorry but what is a GAL?

author: grumpydoc
author_rank: Super Contributor
timestamp: September 28, 2017, 12:11:31 pm
content: Quote from: analogRF on September 28, 2017, 11:38:49 amProgrammable logic

author: analogRF
author_rank: Super Contributor
timestamp: September 29, 2017, 11:30:12 am
content: I have heard that tds700 series are slow and clunky (not only w.r.t. InstaVu as nctnico mentioned but even in general use)compared to lecroy models of the same age like 574/584. Is that a fair assessment?has anyone had experience with LC584 here?

author: JohnG
author_rank: Frequent Contributor
timestamp: September 29, 2017, 01:51:23 pm
content: I had a Lecroy LC574 at my old job for some years. When I got it, I was looking at both Tek and Lecroy, and had prior experience only with Tek. I was biased towards the Tek, but ended up getting the Lecroy. It was far more responsive than the Tek, especially when using any math functions. I ended up liking it a lot.However, after a couple years, Channels 3 and 4 would fail on me. Turned out to be bad relays, which were covered under warranty. The second set failed, and they replaced my scope with a new one, I forget which one. It had Windows and crashed frequently, and did not have filters on the trigger. Oh well.John

author: Ice-Tea
author_rank: Super Contributor
timestamp: September 29, 2017, 02:02:23 pm
content: I'd get the LeCroy. More responsive, bigger screen I think and it's a proper color CRT and not that stupid mono CRT with filter crap. They are not very bright and get a lot worse over time. The LeCroy has more functions directly available under a dedicated button or knob. Takes some getting used to bit works pretty good after that.

author: analogRF
author_rank: Super Contributor
timestamp: September 29, 2017, 03:49:44 pm
content: Quote from: Ice-Tea on September 29, 2017, 02:02:23 pmWhich mono CRT are you referring to? The Tek CRT? But it's a color crt in 754 model. Although I have heard aged Tek CRTs are not bright

author: nctnico
author_rank: Super Contributor
timestamp: September 29, 2017, 03:59:31 pm
content: Quote from: analogRF on September 29, 2017, 03:49:44 pmThe 'color' Tektronix TDS500/600/700 all have a monochrome CRT with an LCD shutter in front of it which produces the colors. These displays are quite fragile in various ways and not easy to fix. Another problem is that these scopes have a dying NVRAM and other parts which may fail. If you loose the calibration you need a DOS PC with a special GPIB card, specialist test equipment and software to recalibrate the scope. Not undoable but it is costly in time and money. I think the Lecroy will be better when it comes to these things.

author: analogRF
author_rank: Super Contributor
timestamp: September 29, 2017, 07:18:38 pm
content: Thank you guys. That was quite a bit of help.I ended up buying an LC584AL with two 1GHz FET probes. I hope I didn't make a mistake and they all work. In pictures they seem ok...it was a risk but I took it... I am gonna need your help to repair it if it doesn't work though !Wish me luck

author: nctnico
author_rank: Super Contributor
timestamp: September 30, 2017, 09:51:36 am
content: Unfortunately Lecroy believes peak-detect is useless. However given the two choices I think the LC584AL is the better choice because it is less old and has more features.

author: analogRF
author_rank: Super Contributor
timestamp: September 30, 2017, 12:52:50 pm
content: Quote from: nctnico on September 30, 2017, 09:51:36 amBut it is still possible to catch rare glitches by setting up a proper triggering and have the same effect as Peak Detect, right?