WANTING TO BUY: 1GHz, 4CH scope - Page 1
Forum section: electronics / general

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 23, 2019, 11:55:35 pm
content: Open to anything out there under $1,000. I have already scoured eBay, and have a few on my list but I wanted to check here as well. Keep the money in the community.

author: rhb
author_rank: Super Contributor
timestamp: January 24, 2019, 02:44:46 am
content: My advice is to get a LeCroy DDA-120 for around $600, strip the CRT and replace with a $90 EBay 7" VGA display. There's a VGA port in in the right rear corner of a DDA-125 which already has the LCD display , Just verify that the 120 also has that.The DDA-120 will sample 4 channels at 2 GSa/S which really only supports a 750 MHz BW, It will sample 2 traces at 4 GSa/S which will support 1.5 GHz and it will sample a single trace at 8 GSa/S which will support 3 GHz.Those BWs are based on having no more than 2-3% over shoot on a 40 pS step.It will require some significant changes. The anti-alias filter used by LeCroy has 20% overshoot. But from examination of my DDA-125, it should be pretty simple to replace the crappy filters with boards with SMA connectors that run to relays in the space where the CRT was and switch between four 750 MHz, two 1.5 GHz and one 3 GHz filter. I've already got the 8 Radiall SMA switches I need. I just need to make the replacement for the factory filters with SMA connectors instead of filters and then make or buy some filters from Mini-Circuits.MSOX3104T has 7% overshoot and an RTM3104 has 10% overshoot with a list in the $20K range. Color me underwhelmed. In fact, I was so disgusted I bought a Tek 485 from Reed Dickinson via eBay just to have a scope that didn't lie to me.The LeCroy will do an XY plot of CH1 vs Integral(CH2) so you can make hysteresis plots. The Keysight and R&S both require an external analog integrator.You might be able to negotiate a swap for a good 4 channel 1 GHz scope with the gear you have, but it won't be easy. Based on my experience with the MSOX3104T and RTM3104 I'm not convinced they exist for my definition of "good" which is 350 pS rise time and 2-3% overshoot.I paid $1000 for my DDA-125 which claims a 1.5 GHz BW, but Nyquist at 2 GSa/S is I GHz, so in 4 channel mode everything above 500 MHz is aliased. That doesn't matter as long as you stay in the time domain, but you're screwed if you do an FFT. But I measure a 220 pS rise time, so it really does have the 1.5 GHz BW. It's a big noisy monster, but I greatly prefer it to the other two. If you go that route look for one with the external reference so you can sync it to a GPSDO.Unfortunately, the DDA-125 requires a scarce external adaptor to merge all 4 channels whereas the DDA-120 does not. All the rest of my HP gear, SA, counter, etc goes to 3 GHz, so I plan to get a DDA-120 , make the changes and sell the 125.If you're looking for a 1 GHz scope, buy one of Leo Bodnar's 40 pS rise time pulse generators from leobodnar.com.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 24, 2019, 03:08:21 am
content: right on mate, thank you.

author: macboy
author_rank: Super Contributor
timestamp: January 24, 2019, 02:15:45 pm
content: I paid around $1200 for a Lecroy WavePro 960, 2 GHz 16 GS/s (4 GS/s in 4 ch) an 16 Mpt memory. The 960 (or 950) does not require the special adapter to merge channels for higher sample rate. One negative of the 960 is that it has a sharp brick-wall filter at 2 GHz. So it does get the advertised bandwidth, but pulse shape suffers. Rise time is slower and overshoot is higher than it would have been with a gradual filter. I guess they did that to avoid aliasing at 4 GS/s 4 channel mode. The DDS-250 and JTA-250 are essentially a Wavepro 950 (>1 GHz) with the disk drive or jitter/timing packages respectively, as well as slightly different button layout on the front panel. Same for DDS-260, JTA-260 which are Wavepro 960 (2 GHz). These all use a 640x480 10" LCD.If you look for any Lecroy, try to get one with good options. Mine has "wave analyzer pro" (option code WAVAPRO) which is fantastic: FFT up to millions of points, histograms, jitter/timing analysis, and much more.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 26, 2019, 06:20:55 am
content: It seems like I will be LeCroy shopping. Thank you both for the input and Ill post an thread once I find my unit.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: January 29, 2019, 06:11:40 am
content: I sent an offer for a DDA-120, well see if I get it. Thanks again for the help.

author: rhb
author_rank: Super Contributor
timestamp: January 31, 2019, 03:23:41 am
content: Good luck and please keep us posted.With five SPDT SMA relays, four 750, two 1500 and one 3000 MHz LP filters it should be a lot of bang for the buck.It would be around $70-100 for filters from MiniCircuits mounted on Rogers or similar RF grade material and about the same for the relays if you're patient. With the proper filter selected you should be able to get 3 GHz single channel performance with a 3% or less overshoot on a step and a 125 pS rise time and a total of 16 Mpts available with correspondingly less BW and depth as you add channels.That's a high end hobby scope in most circles.A lot depends upon whether the AFE has the BW or not. If you feed it to a Zynq, correcting for BW fall off is pretty tractable on a per unit basis.There are a number of important HW options for the DDA-120. The most important being the module to connect to an external (e.g. GPDSO ) clock. The other important option is HD01 which is the PCMIA solid state drive that plugs in the *back*! That takes SD cards via an adaptor. I think all the SW options were hacked long ago, though it's not anything I've paid attention to. My unit came with almost everything you could imagine

author: rhb
author_rank: Super Contributor
timestamp: February 05, 2019, 09:38:17 pm
content: BTW If you get the unit, you should take out the PSU and examine the power connector feeding the main board. Mine is in need of replacement. It's pretty burned up.If the DDA-120 doesn't power up properly it goes into dormant mode. Just the fan runs. Tip off is the yellow "standby" LED. When powered on, that should come on while it is booting. It will then beep twice and put the default display up.If any of the power connectors between the PSU and the main board don't meet spec it just flashes the LED for a second or so and then sits with the fan running. Mine arrived and worked fine the first time. But not the 2nd. So I took it apart. It's a *lot* of work to get all the way to the main board.I wish I had taken pictures, but I didn't. I need to know the details of the connection from the AFE to the ADC. It appears to be a set of LP filters on what looked like a ceramic substrate.My thought is to remove the CRT, replace with a VGA LCD. remove the filters, make a new board to connect in place of the filter board with 2 SMA ports for each channel to go to relays with better filters from MiniCircuits.I really want to control the main board. It might be possible to turn it into a 2 GSa/S 8 bit logic analyzer with a set of ADCMP5xx comparators and setting 4 different voltage levels for each channel. A 16 Mpt deep trace at 8 MSa/S (one channel) . Those comparators would be pricey though.BTW HW options to look for:VGAC VGA screen output critical to replacing CRTGPIBRS-232i2CCKTR external time base for a GPSDO

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 05, 2019, 11:49:03 pm
content: saved this as an '.doc' file as well, for future use...thank you for all the help and advise

author: nctnico
author_rank: Super Contributor
timestamp: February 06, 2019, 12:32:20 am
content: I'd look at HP / Agilent units as well. 54835A or 54845A are nice scopes (the first can be hacked to become the last).

author: rhb
author_rank: Super Contributor
timestamp: February 06, 2019, 01:16:57 am
content: I'm shopping for a logic analyzer to decode the bus ;) I've been shopping from time to timeI want to know how to use the AFE/ADC board of the DDA-120/125 and family with modern computer support (e.g Zynq 7020 or better). I think it has huge potential as the base for a lot of hacking projects. I think a 1-2 GS/S 8 bit LA out of a DDA-120 or 2xx is quite reasonable and inexpensive.You *will* have to write your own software, but that's not that hard.@nctnico, will they display a hysteresis plot without requiring an analog integrator?

author: toastedcrumpets
author_rank: Regular Contributor
timestamp: February 06, 2019, 03:17:04 am
content: Hey,I have a LeCroy 9345AM, with channel combiner and four AP020 fet probes. I think shipping it makes selling you the scope impossible, as it's seriously heavy, but if you buy a DDS-120 I might part with two of the fet probes. Keep it in mind, could just do a swap for some of the remaining standards. The probes are about £100 each on eBay although I got a slight bundle deal when I bought 4

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 06, 2019, 04:12:37 am
content: Well, lets get a DHL quote for a pallet with the unit intact my friend...may work out, may not, but doesn't hurt to try

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 06, 2019, 07:19:30 am
content: i thought you already closed the deal with the DDA-120. why not thinking about getting 5X the BW of later newer model for only 2.5X the price? you might need more and "bigger" in the future! those CRT are getting too old alreadyand people are willing to pay a lot lot more for less the BW and spec just because the units are new

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 06, 2019, 09:05:25 pm
content: Quote from: Mechatrommer on February 06, 2019, 07:19:30 amI send a few bids but didn't win any of them. As I have been kinda spending crazy lately, I am trying to be more reserved. So you think the DD-120 is they way to go? It seem to be the overall conscious.

author: KWKolb
author_rank: Contributor
timestamp: February 06, 2019, 09:27:44 pm
content: LeCroy LC584 is pretty much the same as the DD-120. Depending on the memory depth you need, you could expand your bidding.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 06, 2019, 11:28:05 pm
content: Quote from: KWKolb on February 06, 2019, 09:27:44 pmI think with all the help and advise Ive already received about the 120, I am going to stay in that lane for now, until I learn more myself.

author: tomato
author_rank: Regular Contributor
timestamp: February 07, 2019, 01:07:03 am
content: Quote from: toastedcrumpets on February 06, 2019, 03:17:04 amTypo? 9354AM?

author: CalMachine
author_rank: Frequent Contributor
timestamp: February 07, 2019, 01:18:11 am
content: I've got a Lecroy LC584AL I might be willing to part with!

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 07, 2019, 01:21:40 am
content: Quote from: CalMachine on February 07, 2019, 01:18:11 amFinally, a seller! if you dont want to post $$$ and talks here please PM me and we can discuss it. Though I have to be straight up, the support for the DD-120 is a huge reason I am leaning that way. But I can be swayed. Just need a solid 1GHz unit.

author: james_s
author_rank: Super Contributor
timestamp: February 07, 2019, 01:38:09 am
content: Why strip the CRT if it works? A good CRT looks much nicer than a LCD display any day IMO, much better viewing angle.

author: rhb
author_rank: Super Contributor
timestamp: February 07, 2019, 01:57:51 am
content: OK. The DDA-125 is a DDA-120 with an LCD instead of a CRT and sampling at 2 GSa/S claims 1.5 GHz BW.The 125 requires an external adaptor to merge all 4 channels, the 120 does not. I paid $1000 delivered for my 125. A 120 for $600-700 delivered would be a good price. With the external reference clock module.Had I realized that the VGA option included an internal VGA port I'd have bought a DDA-120/LC584DLX.If you're used to slick BoM optimized instruments, it's not LeCroy. The Lecroys are a series of board revisions as customer requirements changed. My DDA-125 has a 225 pS rise time!, Of course, the overshoot is 20%.The big issue is getting data off the scope. To write to an SD card via a PCMI/SD adaptor you have to have the HD01 HW option which installs on the *back* of the scope!Stray observation: A 120/125 samples at 2 GSa/S. With a pair of ADCMP58x per channel you could have a 8 GSa/S, 16 Mpt deep 8 bit logic analyzer. That's the performance level of a *really* expensive LA.You don't want to touch anything that the seller doesn't show the STATUS->SYSTEM screen, though you may have to ask Actually, asking for photos of all the 5 status pages is a pretty good test of a functional unit barring blown AFE/ADC sections. A BNC jumper and the "auto setup" will verify the rest of the operation.The cost of shipping is such that if you agree to pay return shipping, you can get return privileges.For reference, the *calibrator* on the DDA-125 will supply 25 nS pulses at up to2 MHz which have 500 pS 10% - 90% rise times.FWIW I've been wondering if a DDA-120 might not be a better platform for developing FOSS DSO FW. As general bang for buck you can't beat Rigol , Siglent, OWON, etc at the low end. But because of the commonality of parts on low volume, custom instruments, a little extra work with a logic analyzer might make a LeCroy disk drive analyzer a very desirable property.

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 07, 2019, 06:44:02 am
content: Quote from: Inverted18650 on February 06, 2019, 09:05:25 pmmy journey few months ago started looking at this kind of DDA-120 1GHz thing (yes there are lot of discussions and repairs going on here and in the net), then i saw DDA/SDA like lecroy scope. wavepro 950/960, hey thats small addition of money. and then DDA3000 hey thats small addition of money, and then 5005 and then 6000. 11000? well thats a big addition of money i cannot go. now with some financial damage, i can still smile. its good to be around this baby, its like having a good day every dayalbeit the SWMBO noise ratio went high. well looking back from where i started, i've multiplied the cost 2-3X from where i originally expected (excluding accessories needed probes adapters etc), but at least i know with some uneducated level of confidence i can have a long time playing with it, and also now i can see whats going on in my 5.8GHz wireless video system in time domain in 8 bits level not 1 bit or in logarithmic scaleat least teardown shows circuitry still in their pristine conditions albeit with some dust settled down. whats hurting me is when thinking we spent $1K or a little bit less, and the unit burn up in few weeks of time due to age, and we go back square one to where we started, looking and bidding again. or at least finding resources in the net and forum on how to repair it, still requires money for parts and time for repair.now i have 2 of this wavemaster, the first one got me learnt about the system, with some level of confidence i grab the 2nd one at i can say bargain price (i think even cheaper than current DDA120 price) because they dont know how to recover unbootable windows disk. that was an easy fix (according to my scale) i dont even have to hack to put calibration data of 6000 into 5005. i've lost 2 auctions of SDA6000 in few weeks back at around $700 (excl shipping, shipping is another hurting aspect if from USA) but you must have a know how to fix Windows system and in case you've lost the scope CAL data, you must have someone else providing it to you. since now i can view 6GHz in analog domain, the hunt now is on 26+ GHz SA because my "1yrs old with me" 8GHz SA seems lagging now, this i think is some type of lead poisoning syndrome but hey who cares as long as it feels good... fwiw ymmv.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 07, 2019, 06:45:07 am
content: Its called T.E.A. and the time domain is just as addictive as the volt-nuts get with our gear....I am crossing over into both worlds and about to break the bank! Just got my 1st ever new bench top DMM, a Keithley DMM 7510...and I really really want to get my FREQ on.The support you all have given here is increible and I read and re-read all your threads, because for me its extremely valuable knowledge you are sharing. Many thank you's...and Prost!

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 07, 2019, 07:15:15 am
content: Quote from: Inverted18650 on February 07, 2019, 06:45:07 amyeah i guess so but luckily so far i've not yet get sucked up by "super accurate super stable" DC volt syndrome. a part of the help are some discussions here on Windows system, registries, CAL data and option "licensing" on Lecroy's scope, and currently there is continuing effort to study the probe interface, this should and hopefully bring Lecroy's name into the eyes of hobbiests more and more, (this can be viewed as good or bad for Lecroy) so kudos to those contributors.

author: Inverted18650
author_rank: Frequent Contributor
timestamp: February 08, 2019, 06:31:17 am
content: I was laid up again today with a bad back and spent some time on eBay. I found a couple nice used Tek 1Ghz or better scopes under $1k from what appears to be a fellow Tek junky, only this pesron deals with units post 80's, (Id guess).So I found a 4CH, 3Ghz unit that has a bad trigger on Ch3&4, but its 3GHz/ 10GS/s on the working two channels. I think the other two function a bit lower, need to find out in the a.m.I also found a nicely modified TDS654C, up to the TDA684C with 1Ghz/ 5GS/s , and it has a couple extra options.The seller has a few more but I leaning toward either of these two if I cannot find a DD-120/ or 125 that I can buy.Any feedback about these units? Are any of you the eBay store owner, fellow Tek-nut, I am referring to who is selling these units?

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 08, 2019, 09:31:13 am
content: eevblo-googl-lo result....TDS654C...https://www.eevblog.com/forum/buysellwanted/wanting-to-buy-1ghz-4ch-scope/msg2186312/#msg2186312only one hit, wait a minute, that is this thread! that should tell something...TDA684C...https://www.eevblog.com/forum/buysellwanted/wanting-to-buy-1ghz-4ch-scope/msg2186312/#msg2186312this thread again...TDS694C...https://www.eevblog.com/forum/repair/tektronix-tds694c-triggering-chips-mystery-solved/msg1500856/#msg1500856https://www.eevblog.com/forum/testgear/tektronix-tds500600700-nvram-floppy-dump-tool/msg2127817/#msg2127817https://www.eevblog.com/forum/repair/looking-for-someone-who-can-replaceswap-tek-tds694c-trigger-chips-for-$/msg1186021/#msg1186021https://www.eevblog.com/forum/repair/calling-all-tek-tds694c-experts-i-need-help!/msg1236856/#msg1236856https://www.eevblog.com/forum/testgear/least-expensive-but-reliable-used-market-scope-with-at-least-1-ghz/msg791170/#msg791170https://www.eevblog.com/forum/testgear/agilent-54835a-scope-(4-channel-1ghz-4gss)-repair-uphack/msg1251605/#msg1251605and some others. so at least there are something you can guesstimate what will you be dealing with. be ready with a floppy disk and GPIB interface, and a hot plate if you are unluckygood luck anyway.