Having issues with channel one on my Siglent scope, is this hardware? - Page 1
Forum section: electronics / repair

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 28, 2016, 06:49:23 am
content: Ok so I bought a Siglent 25Mhz 1022DL on the forum about 1.5 years ago. When I first got it I upgraded all the firmware bought quality american probes, and compensated them. I know at that time there were no issues with the scope. For about the last 8 months Ive mostly used it for its FTT functions in AC coupled mode, so im not even sure when this issue popped up. On a freshly calibrated probe channel one is not properly displaying the 100khz square wave on the output, the rising edge is awful. I hooked a probe to the 100khz output then set both of the channels for the same voltage/timing, here is what im seeing.Probe on channel #2Same probe same settings on channel #1Now here is what channel #1 looks like when the waveform is scaled to fit in the y axisI really can't afford to replace the scope... and im really hoping this is not a hardware problem but I hit the defualt setup button a few times and I even relashed the firmware. I use my scope for the things I need so I don't know all the nooks and crannies in scope software im hoping maybe I changed some stupid setting that isn't changing back... Thinking about this issue if its hardware I don't think it is anything to terribly wrong aybe just some bad caps or something in the front end screwing up the impeadence/filtering/compensation? The thing is Ive never used this scope for anything more than 5 maybe 12v, for the most part and ive never smoked anything while testing so im not sure why anything in the front end would be messed up.So has anyone seen something like this before? Hopefully have some good news so I can get back to work!

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2016, 07:14:52 am
content: Ch 2 looks like it's working as expected.Weird, nothing comes to mind immediately as to why Ch 1 is behaving that way.I'll point Siglent support to this thread and hopefully they'll offer some advice.

author: singapol
author_rank: Frequent Contributor
timestamp: October 28, 2016, 09:25:13 am
content: What I can see is ch2 is "armed" trigger so what is triggering it, whereas ch1 is normal "triggered" ?The measurements in pic1 and 2 is different for Vpp and Vmax.

author: mij59
author_rank: Frequent Contributor
timestamp: October 28, 2016, 09:53:00 am
content: Try a time base setting of 5 usec, looks like aliasing.

author: Arjan Emm
author_rank: Regular Contributor
timestamp: October 28, 2016, 11:38:55 am
content: Quote from: mij59 on October 28, 2016, 09:53:00 amBoth channels should show aliasing the same way, i'd guess?

author: 3db
author_rank: Frequent Contributor
timestamp: October 28, 2016, 12:01:42 pm
content: Have you tried both probes on the working channel ?3db

author: mij59
author_rank: Frequent Contributor
timestamp: October 28, 2016, 12:13:36 pm
content: Quote from: Arjan Emm on October 28, 2016, 11:38:55 amYes thats a bit strange, let ask Siglent.I both cases the frequency measurement is wrong.

author: StillTrying
author_rank: Super Contributor
timestamp: October 28, 2016, 01:37:07 pm
content: Assuming the waveform is the scope's 1khz 3V p-p compensation signal, and one channel's X10 is wrong, then all the frequencies and voltages are correct!Low pass digital filter set on ch1?

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 28, 2016, 07:04:41 pm
content: Ive tried both probes, on both ports same thing.As far as the digital LP filter, I believe this may be the problem. A while back I was designing a 7 pole 30mhz LP and I went futzing around with the digital LP filtering in the scope to see how well it worked. The thing is when I hit ch1 the third page of the menu is for digital filtering and it is all turned off, maybe there is a setting somewhere else I dont know about or something. Iv'e been through all the menu's but I know the scope has and X,Y view and I haven't seen that either so I know there is some settings somewhere I'm missing. Hitting the return to defualts button and reflashing the firmware doesn't wipe all the settings I know this because me measurement menu has never changed from my set up. Is there a soft reset or something?So this obviously isn't a problem commonly seen on a DSO, and most likely not hardware? Oh and it passes all the self cal and self testing.

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2016, 07:22:52 pm
content: Just to be sure, in the OP you mentioned 100 KHz, don't you mean 1 KHz ?If you're using the probe cal output, then what's on the display doesn't match the channel settings.....3 V amplitude should be 6 divisions @ 500mV/div.It seems to me that you haven't set the input attenuation to match the probe's attenuation, check that will you.EditAnother trick is to push the Trigger level adjust knob, that autosets the Trigger level to 50% of the waveform.Also, check the Ch 1 BNC for rigidity just in case the mount is broken, I've not seen this on Siglent's, only on other scopes and it might explain an unexpected waveform.

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2016, 08:12:24 pm
content: What's the DSO's SN #, we don't need the last 4 digits but the ones prior to them signify the build date, it might sill be under warranty.

author: nctnico
author_rank: Super Contributor
timestamp: October 28, 2016, 08:16:48 pm
content: Isn't there an 'auto setup' or 'default' button on the scope? I'd try that.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 28, 2016, 09:55:51 pm
content: I have pressed the auto set button a few times.Im sorry somehow channel 1 was not at 10x, and I did mean 1Khz not 10Khz. Here is a picture of the waveform at 500mv 10x setting and the Auto 50% Trigger button pressed.The SN# sds00001130545, that would be great if it was under warranty but it's an older model so im sure im not that lucky.

author: tautech
author_rank: Super Contributor
timestamp: October 28, 2016, 10:19:38 pm
content: 0113 signifies Jan 13 build but have you got proof of purchase and exact date ?I'll get a similar scope out in the next day or so and see what I can do to replicate your fault.

author: edpalmer42
author_rank: Super Contributor
timestamp: October 28, 2016, 11:15:50 pm
content: On a square wave, when you lose the horizontal parts of the signal, that means you've lost your low frequency response. If you lose the vertical parts of the signal, you've lost your high frequencies. If you have a signal generator, check your low frequency response to see where your -3dB point is. That might help determine whether you're looking at a software glitch or maybe a cracked solder joint.Ed

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 28, 2016, 11:56:00 pm
content: I leant my Sig gen out to a buddy(it's only 2mhz), I could sweep the scope with a sound card gen to find the -3db point right? I mean it should be well under 1khz based on the wave form, idk if a sound card can output under 2khz.As far as proof of purchase, I bought it working last year on the forum, from a member in the eu. It was bought for one of his clients who bought a Tek and never used it. So does not having the original purchase date with proof mean I'm out of luck?

author: tautech
author_rank: Super Contributor
timestamp: October 29, 2016, 12:14:23 am
content: Quote from: rwgast_lowlevellogicdesin on October 28, 2016, 11:56:00 pmI was just trying to investigate with you IF you had the original purchase documents, obviously not.Even though we've established a Jan 13 build, I often get new units from the factory that are already some months old, that is they're produced in batches, held as stock then shipped only then to be probably held in stock again by the distributor before sale to the user.Get the picturesome units that I might have on hand are 12 months or so since their build date before sale to a end user. I warranty Siglent units for 3 years from date of purchase.So if there's any chance you can find out the original date of purchase and from which dealer AND if it's a HW failure there might be hope for a warranty claim.Then again, if this DSO suits your requirements we might be able to arrange a replacement MB from Siglent if we don't pursue a repair.

author: Anks
author_rank: Frequent Contributor
timestamp: October 29, 2016, 04:53:29 am
content: I would expect a bad coupling cap. Its acting like a high pass filter. Just how it looks to me.

author: StillTrying
author_rank: Super Contributor
timestamp: October 29, 2016, 06:21:57 pm
content: Random thoughts time.(is there any other type)While you're playing it might be worth keeping both probes and both channels on X1, to eliminate one variable.Is it the same shape with AC/DC ch1 coupling.View the 1khz on both channels at the same time, just in case ch1 is loading the signal somehow.Enable the digital filter on ch1 and try some settings to see if they change the waveform, set a LP of a few Mhz, if the filter settings have been corrupted somehow rewriting new values might fix it, including the on/off.Try capturing some fast rising edges, just from a 1.5V battery would do, ch1 only seems to rise about 200mV before it has a problem.200hz to 5khz 1V square waves from a sound card might help to give a clue what it's doing.Well I did say they were random!

author: tautech
author_rank: Super Contributor
timestamp: October 29, 2016, 06:51:55 pm
content: Quote from: rwgast_lowlevellogicdesin on October 28, 2016, 07:04:41 pmI had a good crash around in the UI and menus of a new SDS1kCML+ unit while I was doing a presale check, I got all sorts of strange waveforms from the probe cal output using the inbuilt filters and other settings but I could not replicate anything that looked like yours. Defaults etc all worked as expected too. So I strongly suspect there's something in your Ch1 signal path faulty but I do have a MB here and I'll have a look at the input stage for you........

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 29, 2016, 07:22:47 pm
content: Sorry iv'e been a little busy doing Halloween activities with my daughter. Thank you for checking around the software for me, I will get a message to the original buyer today to see if he has any proof of purchase or any info on the date/distributor the scope was bought from.My digital filtering settings wont go above a few hundred Khz and my Acquire menu shows 2.5Msps (with one channel only) even though its a 500Ms scope, is any of this normal? I printed out some copys of the manual a while back I need to bust out but I would think set defualts should have fixed any goofy software settings :/. Ill also run some tests with my soundcard and post pics ASAP.

author: tautech
author_rank: Super Contributor
timestamp: October 29, 2016, 08:00:12 pm
content: From an old thread by rf-loop:https://www.eevblog.com/forum/reviews/siglent-sds1000-7'-oscilloscope-anatomy/These look exactly the same as a MB I have here and my pics wouldn't be as good so I linked these.MBUndersideCh inputI'm not sure if there's any reverse engineered schematics for the SDS1k channel inputs, someone following may know of them and hopefully provide you with a link.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 29, 2016, 08:43:40 pm
content: Damn, I dont think I would even know where to begin there are so many discrete smt components, especially if your not sure what values they are suppose to be in the first place. Ill usually rip anything apart and give it a try, but im a bit scared to screw up my scope and on top of that I wont have a scope to help trouble shoot anything on the mobo. I have some old rack mount HP analog but it is only 500khz so I dont think that will help me at all.Do you know what it would cost me to order a new mb, or if maybe I could upgrade to a better bandwidth scope with a drop in mobo replacement?

author: tautech
author_rank: Super Contributor
timestamp: October 29, 2016, 08:57:22 pm
content: Quote from: rwgast_lowlevellogicdesin on October 29, 2016, 08:43:40 pmI'd hope that it would be possible to follow the signal path with the good channel on your DSO, but a schematic is needed as these are a multilayered PCB. Values, don't worry about them, I've got your back with a MB on hand.This one has a corrupt LCD output but the CH inputs are good.Until we get hold of Siglent (weekends) I couldn't say. They've been very helpful to forum members in the past, so let's just give it a bit more time to see what can be arranged.Where in the US are you ?At some point we'll probably hand over to some of the Siglent folk at Ohio to help get this sorted for you.I can't say (don't know) what stock of parts they have on hand or if bits would need to be sourced from the factory.Sit tight for a few more days then we'll know more.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 29, 2016, 09:18:07 pm
content: Im in southern california about 100 miles from LA near Palm Springs. Thanks for everything, a lot more than I expected when I opened this thread.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 29, 2016, 09:58:34 pm
content: Ok so a sound card puts out awful square waves at any frequency but with some I can clearly tell the wave form distorts in between 60-65hz, that is when the rising edge disappears and it becomes more of a triangle/sin wave. Sin wavs seem to look fine but a I get faster well into the khz range they skew a little bit on the falling edge in a subtle sort of concave manner.Is it coincedence that this problem starts about the same frequency as the mains voltage?

author: 2N3055
author_rank: Super Contributor
timestamp: October 29, 2016, 10:08:09 pm
content: Sorry if I'm asking the obvious but there is button "Default setup" that should reset all the user interface setting to defaults...

author: DimitriP
author_rank: Super Contributor
timestamp: October 29, 2016, 11:59:58 pm
content: QuoteIf you are trying to trace a 1KHz signal, it should work just fine. (if that's indeed a "rack mount" 500Khz scope- check again!)Feed both channels with 1KHz and then use your 500KHz scope to trace the signal, comparing ch1 with ch2.Buit if there is a chance it's under warranty, you should probably wait to know for sure before you start tearing it apart.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: October 30, 2016, 01:26:52 am
content: I have repeatedly said I have hit the default set up button at least 5 times...Im positive the scope is 500khz, its a huge beast. I cant even fit the thing on my desk id sell it if it were worth anything I figure its good for audio. I see people trying to get 300 bucks for it on e-bay I have no idea what there thinking... If I could get that I would sell it in a heart beat a signal gen or to put twords a LimeSDRhttp://www.radiomuseum.org/r/hewlett_pa_oscilloscope_1200_b1200.htmlhttp://www.ebay.com/itm/HEWLETT-PACKARD-1200B-OSCILLOSCOPE-100uV-DUAL-TRACE-500KHZ-/281860857463

author: StillTrying
author_rank: Super Contributor
timestamp: October 30, 2016, 03:08:22 am
content: Quote from: rwgast_lowlevellogicdesin on October 30, 2016, 01:26:52 amActually, hitting the 'Math' button 5 times, might do some resetting or something.

author: tautech
author_rank: Super Contributor
timestamp: November 01, 2016, 06:43:31 am
content: @ rwgast_lowlevellogicdesinYour issues have been handed to Siglent USA, there will be less of a difference in time zones in order to find a solution for you.Expect contact from them.

author: villas
author_rank: Newbie
timestamp: November 01, 2016, 11:38:00 am
content: I have a working 1022DL, let me know if there is something I can check on my unit to compare.

author: sdrocco
author_rank: Newbie
timestamp: November 01, 2016, 03:42:59 pm
content: At Siglent America we have not seen a problem like this before on any of our oscilloscopes. The SDS1022DL was never sold through the US office, but in my opinion it looks like a hardware problem. If you would like you can contact us at info@siglent.com.

author: tautech
author_rank: Super Contributor
timestamp: November 01, 2016, 05:29:39 pm
content: Quote from: sdrocco on November 01, 2016, 03:42:59 pmWelcome to the forum Scott.Yes, I've not seen the likes of this problem before either.Is it possible rwgast_lowlevellogicdesin can be offered a 1052DL mainboard?

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: November 02, 2016, 06:29:53 pm
content: Well thanks for getting back to me guys :/. Sucks this is hardware.

author: StillTrying
author_rank: Super Contributor
timestamp: November 03, 2016, 03:24:37 am
content: So what's the plan now. I had a good search for a schematic, I didn't try for ATTEN versions though.

author: DimitriP
author_rank: Super Contributor
timestamp: November 03, 2016, 04:03:32 am
content: Time to take it apaaaaht !

author: DimitriP
author_rank: Super Contributor
timestamp: November 03, 2016, 04:24:08 am
content: Found the "Service Manual" but it doesn't include a schematic. Genius!!!Still, Ch1 and Ch2 are "twins".You should be able to compare signals to find out where the signal gets lost. So lug that 500KHz scope out and fire it up.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: November 03, 2016, 07:37:44 pm
content: Im going to call siglent today and get a few answers about compatible motherboards, warranty etc. Im afraid to take an iron to the mobo having a 1 channel scope is better than a no channel scope. Looking at the pictures posted im not sure this repair is in my league yet. I will get my siggen back today so I can run some better tests, if worst comes to worst I may open it up and try to trace the signal with my other scope but i trying to avaoid poking around in it.I seriously thought that this would be a problem with some of the filtering hardware in the front end but the fact that it starts at 60hz from what I can tell is just to coincidental.

author: BravoV
author_rank: Super Contributor
timestamp: November 03, 2016, 07:44:20 pm
content: Your scope is already out of warranty right ? Are you saying Siglent willing to repair or even better send you a new board "for free" ?

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: November 03, 2016, 08:41:26 pm
content: No... I'm not sure of anything I'm going to call and figure out my options. I doubt anything will be free, but if I can use other motherboards in the same chassis with the same screen/controls that opens up a lot more options.

author: DimitriP
author_rank: Super Contributor
timestamp: November 03, 2016, 10:41:06 pm
content: Open it up already

author: tautech
author_rank: Super Contributor
timestamp: November 03, 2016, 10:57:43 pm
content: Quote from: DimitriP on November 03, 2016, 10:41:06 pmWhy ?There won't be anything different to see than in the pics in reply #21.If rwgast_lowlevellogicdesin has some capacitance and resistive measurement equipment maybe we can help to check values of what he measures, but let's see what Scott from Siglent America can put together for him first.Quote from: rwgast_lowlevellogicdesin on November 03, 2016, 08:41:26 pmOnly if Siglent are happy with sending you other model decals for the front panel too.It is likely any replacement mobo will need to come from the factory where it will be configured to the correct model.If warranty applies, rwgast_lowlevellogicdesin will get the same as he already has.Either way, any replacement mobo will come with a different SN# and a new SN# label for the enclosure.EditSpelling

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: November 09, 2016, 02:40:30 am
content: @tautech, I sent you a PM. I talked to scott today beside trying to trace a signal through the front end with no schematics a 1052 mobo is about my only option.

author: tautech
author_rank: Super Contributor
timestamp: November 09, 2016, 06:45:19 am
content: Quote from: rwgast_lowlevellogicdesin on November 09, 2016, 02:40:30 amGot it, been out all day.I see little reason why if you dismantle the scope, then reconnect all cabling, why you couldn't trace the probe Cal squarewave in the broken channel with the good going one. Be sure to disconnect the Reference (Gnd) of the probe you use and place the sleeve on that covers the reference ring near the point.This will test your detective work, but before you get ahead of yourself, first identify the active components in the channel input. Datasheets can save your bacon, they often have typical circuit examples and in this case the IC's used are likely scope input specific. This will give you little snapshots of the schematic, most likely enough to give clear points where you can test the signal path. While this might not point to the exact fault, it will narrow the fault to a smaller section, at which point you may be able to find a single faulty component.Now for any in-circuit passive measurements, grab the pic I posted before of the input section and edit it pointing to any components and I'll measure them on the Mobo I have.Good luck.BTW, a very careful inspection of all the solder joints would be what I did first.

author: rwgast_lowlevellogicdesin
author_rank: Frequent Contributor
timestamp: November 09, 2016, 08:22:52 pm
content: Have you opened up one of these guys before, are you able to physically probe the front end with out removing the whole unit screen and all and then reassembling on the bench?Second instead of worrying about earth ground problems and screwing with the probes, am I able to just use a cheater plug?

author: tautech
author_rank: Super Contributor
timestamp: November 10, 2016, 01:13:19 am
content: Quote from: rwgast_lowlevellogicdesin on November 09, 2016, 08:22:52 pmOnly CNLs and CMLs but the DL will be very similar. You will likely have to completely dismantle the scope, front panel too.There is too much risk not to cover the gnd ring on your probe. Just do it please and forget any ideas of isolation, it only gives a false sense of security in this case and is quite unnecessary.