VOLTCRAFT DOV series

[Aldo22]

Which just proved that quality assurance hadn't even looked into the problem.
I would resend the images showing the 200 mV issue, along with the images from XY mode and the FFT.
Then they should be able to reproduce it, and if they still think it's a user error, well, then they should show how to operate it correctly.
I'd be very surprised if that were possible.

I see what you mean, and in a way, you’re right, of course.
But there’s also such a thing as peace of mind, and I don’t know if this matter is worth the trouble to me.
In the end, I’ll find myself in a legal battle with Conrad, and these little flaws aren’t worth it to me.
I wish the defect were more obvious.

I mean, I paid 149 for it.
If I didn’t have the comparison from your images, I would have thought: OK, that’s just how it is. No FFT beyond 1k memory depth—
what can you expect for that price?

[KungFuJosh]

If they tell you it's an operator error, tell them they're wrong. Tell them you can provide screenshots from 5 other people with the same error. Ask them for an email address, and ask the other people here to send screenshots directly.

[Martin72]

I can't stop thinking about the 200 mV issue, especially since I still haven't received a response from Owon.
The ripple itself has a frequency of about 40 kHz—instead of struggling with the cursors, I did the obvious thing this time and ran an FFT....
You can see for yourself with the scope that the ripple is “real”—by using the FFT there.
You can also see how the peak disappears when you select a different vertical unit.
I know that the ripple is present when a relay switches—it essentially turns on the interference.
Using a Siglent oscilloscope and a probe set to AC coupling, I measured the op-amp whose output goes directly to the relay contact.
The interference is already present at its input (measured at the series resistor).
As is the case everywhere, it’s at the same point on every channel.
This input is fed by another op-amp, whose output supplies it.
However, this op-amp is on the other side and therefore cannot be actively measured....
Oh, I wish I could get more information from Owon.
But I doubt I’ll get any useful answers from them.

(Notes:
The power supplies for the OP are +5V and -4V; the “invisible” OP, on the other hand, is powered by +5V (the same 5V) and -5.3V... For whatever reason.)

[Aldo22]

If they tell you it's an operator error, tell them they're wrong. Tell them you can provide screenshots from 5 other people with the same error. Ask them for an email address, and ask the other people here to send screenshots directly.

They don't care about that. Why should they?
The manufacturer's device (Owon ADS800A) shows the same fault, and they obviously don't care about that either.
I don't expect Conrad to fix Owon's bugs.

[KungFuJosh]

If they tell you it's an operator error, tell them they're wrong. Tell them you can provide screenshots from 5 other people with the same error. Ask them for an email address, and ask the other people here to send screenshots directly.

They don't care about that. Why should they?
The manufacturer's device (Owon ADS800A) shows the same fault, and they obviously don't care about that either.
I don't expect Conrad to fix Owon's bugs.

Because it's not user error; that's why they should care. Showing that a bug is consistent across multiple devices for multiple users proves you're not at fault.

Also showing other things such as @Martin72 demonstrated will show further issues with your scope.

Finally, it's a cheap piece of shit. They don't care about it. If you give up easily on it, you will eat the cost. If you stand your ground and give evidence that there's an issue, they'll gladly replace the cheap piece of shit with a (hopefully better) cheap piece of shit. It's not worth their time to argue over it.

[evava]

If they tell you it's an operator error, tell them they're wrong. Tell them you can provide screenshots from 5 other people with the same error. Ask them for an email address, and ask the other people here to send screenshots directly.

They don't care about that. Why should they?
The manufacturer's device (Owon ADS800A) shows the same fault, and they obviously don't care about that either.
I don't expect Conrad to fix Owon's bugs.

Look at it another way, the way you describe it, it wouldn't make any sense to buy anything from local sellers with a warranty. It would be better to buy the device on Banggood or Aliexpress or anywhere else in China. Plus, you can usually send a picture or video there and at least negotiate a discount with the seller.

From the beginning I think that the strange 50% discount has a reason, the sellers just modestly keep it a secret.

I'm also keeping my fingers crossed for Martin that he can fix it!

[Aldo22]

Because it's not user error; that's why they should care. Showing that a bug is consistent across multiple devices for multiple users proves you're not at fault.

Finally, it's a cheap piece of shit. They don't care about it. If you give up easily on it, you will eat the cost. If you stand your ground and give evidence that there's an issue, they'll gladly replace the cheap piece of shit with a (hopefully better) cheap piece of shit. It's not worth their time to argue over it.

Yeah, right, in a perfect world.
After Conrad gave that idiotic answer, I wrote that this is demonstrably false.
I haven’t heard anything since.

Should I hire a lawyer over this nonsense?

Last year, I spent months arguing with PayPal, to no avail.
I’m sick of this crap.

[KungFuJosh]

Yeah, right, in a perfect world.
After Conrad gave that idiotic answer, I wrote that this is demonstrably false.
I haven’t heard anything since.

Should I hire a lawyer over this nonsense?

Last year, I spent months arguing with PayPal, to no avail.
I’m sick of this crap.

Then the only question is whose time is it worth less of?

Did you follow-up with them after that email? If you're annoying, they'll take care of it. If you forget about it, they won't.

[PhilRépartout]

argument about rebate because of the bug seems not to be valide as Owon price have normal price with same bug.

never forget their time cost is WAY more than your time and letting this go is encouraging crap material to be the new norm !
the only thing which permit them to sell crap products is sells money they make is superior to money value it cost them to answer and correct problems... if enough people don't let go, only serious companies and good customer services stay , others will not make profits anymore.

your porblem is very simple to present to conrad:

you say it's a user error ? good to knwo so there is a solution !
so here is MY video showing the problem on youtube for every body on this planet, on the comments sections i will indicate i asked Conrad to show me the "good pratice" to not make such "user error" and have right scope results, so i will post an update of this video with the CONRAD good pratice no error usage of this scope...

give them nightmares and make fun about it you will see it's not boring anymore to ask them to have a customer service....
otherwise everybody will bought directly from China...

[Aldo22]

I'm not going to save the world. 
I'm not going to fight. I'm tired of fighting for things like that.
The ripple bug won't be fixed by Conrad or Fujian Lilliput Optoelectronics Technology Co., Ltd. anyway, and I don't want my money back either.
For 149.-, I can't think of a better oscilloscope, despite the few flaws. I can handle them all.

[Olex]

For 149.-, I can't think of a better oscilloscope, despite the few flaws. I can handle them all.

I'll second that!
Personally, for a relatively low price, I got an interesting device with great potential, even if it comes with its share of issues.
But solving these issues is actually fun for me 

[KungFuJosh]

I'm not going to save the world. 
I'm not going to fight. I'm tired of fighting for things like that.
The ripple bug won't be fixed by Conrad or Fujian Lilliput Optoelectronics Technology Co., Ltd. anyway, and I don't want my money back either.
For 149.-, I can't think of a better oscilloscope, despite the few flaws. I can handle them all.

I thought your scope had a unique failure the others did not? Or did you resolve that?

[PhilRépartout]

I'm not going to save the world. 
I'm not going to fight. I'm tired of fighting for things like that.
The ripple bug won't be fixed by Conrad or Fujian Lilliput Optoelectronics Technology Co., Ltd. anyway, and I don't want my money back either.
For 149.-, I can't think of a better oscilloscope, despite the few flaws. I can handle them all.

"world" is what you make of it ...   nothing more ... nothing less

[Aldo22]

I thought your scope had a unique failure the others did not? Or did you resolve that?

Yes, that's true. There are issues with FFT and XY mode at higher memory depths.
Of course, I'm interested in whether and how I can fix or work around these errors.
But they aren't important enough to me that I would send the device back and get into a dispute with the seller.

[Aldo22]

"world" is what you make of it ...   nothing more ... nothing less

Why me?
Everyone here who owns this device has the ripple issue, yet they still keep it.
Mine is the cheapest one, besides.

[Martin72]

I don't think these are bugs, but rather a real flaw in your Scope.
But in the end, of course, it's up to you to decide what to do about it.

Fan:
It arrived, looks high-quality, and has a different connector.
Good thing I have a selection of JST connectors and connector housings...
So I swapped it out and was happy—this fan is much quieter than the original one.
Sure, you can always hear a 60mm fan, but this Noctua whispers rather than “roars”—and in a pleasant tone, too.
This Noctua runs constantly, even during the boot phase, but that doesn’t bother me.
All in all, I’d recommend it.

[KungFuJosh]

I thought your scope had a unique failure the others did not? Or did you resolve that?

Yes, that's true. There are issues with FFT and XY mode at higher memory depths.
Of course, I'm interested in whether and how I can fix or work around these errors.
But they aren't important enough to me that I would send the device back and get into a dispute with the seller.

You'll make your own decision of course, but were I in that situation, I would have returned it already for a replacement...or just a refund and moved on.

I see the appeal of the scope as a project toy, but hw defects on a new product would bother me.

[adam4521]

@Martin, your captures appear to show that the ripple is passing through the opamp, not created there, nor 'caused' by the power supply there. To eliminate the coil as a source, is the coil voltage itself reasonably clean? Would it be worth checking smoothness of other power nodes? I'm struggling to think of other ways that the ripple can be introduced to the front end, especially given the understanding that it goes away if MSO parts are populated.

[Martin72]

Hi,

That’s what’s bothering me, too.
As for the relay coil, there’s nothing much to see there.
The relay does have a (connected) changeover contact.
The signal with the interference is already present at the NO point even though the relay isn’t active—that’s the point.
So we can rule out the relay as the source of the interference.
And yes, the op-amp on the “visible” side basically just passes the noise along—it’s already present at its input.
Or rather, I’d have to check that again, because the input is, of course, connected to the output via the negative feedback resistor.
The real question is, where does this 40 kHz come from...
Every channel in the front end has it.
I’ll have no choice but to trace this 40 kHz signal back further, hopefully all the way to its source.
And why is this phenomenon no longer present in the MSO variant....

[Martin72]

Here is a slightly more detailed schematic that I was able to create by measuring the circuit.
The component with the code “ST3SK” has me a bit stumped.
Is it another op-amp, or is it something else....
In any case, the ripple can be measured at the output of the first op-amp, then at the output of the second, where it goes to the relay contact.

[KungFuJosh]

Here is a slightly more detailed schematic that I was able to create by measuring the circuit.
The component with the code “ST3SK” has me a bit stumped.
Is it another op-amp, or is it something else....
In any case, the ripple can be measured at the output of the first op-amp, then at the output of the second, where it goes to the relay contact.

Did you take any photos of it?

[Martin72]

Yes.

[KungFuJosh]

From your drawing, it looks like a switch. However, your pin numbers are not something that matches any parts I've checked. It's possible the numbering is incorrect, as those SOT chips sometimes follow different numbering patterns. Is the attached numbering what you followed?

[Martin72]

Yes, you have to decide on something.
My assumption is based on the “classic” SOT23-5 pinout.
Under “3SK,” you'll find voltage detectors in SOT23-5 packages; it could be possible, but the symmetrical power supply presents a challenge.

[Olex]

So, here is the fix for the fan speed control, which was broken in the new firmware version (V1.0.1.0.17).

Installation:

Copy the fanfix.tar archive to a USB flash drive, then connect the flash drive to the oscilloscope.

Connect using adb:

Code: [Select]

$ adb shell
DS01:/ $ su
Please input root password:
DS01:/ #

Copy fanfix.tar to the local storage:

Code: [Select]

DS01:/ # cp /storage/1BFA-0317/fanfix.tar /data/local/tmp/
Note: 1BFA-0317 is the unique ID of your flash drive.
You can check yours by running

Code: [Select]

DS01:/ # ls /storage | grep -Ev "emulated|self"

Go to the local directory and extract the archive:

Code: [Select]

DS01:/ # cd /data/local/tmp && tar xvf fanfix.tar && cd fanfix
fanfix/
fanfix/install.sh
fanfix/init/
fanfix/init/fanfix.rc
fanfix/bin/
fanfix/bin/fanfix.sh
fanfix/bin/libxds.so
fanfix/bin/fpgawrite
fanfix/uninstall.sh
fanfix/src/
fanfix/src/Readme.txt
fanfix/src/fpgawrite.c
fanfix/Readme.txt
Install the fix:

Code: [Select]

DS01:/data/local/tmp/fanfix # ./install.sh
Installing fanfix files
Testing fanfix once
Installing init rc
Installed. Reboot device to activate autostart.
Reboot the device:

Code: [Select]

DS01:/data/local/tmp/fanfix # reboot

Uninstallation:

You can remove it like this:

Code: [Select]

DS01:/ # cd /data/local/tmp/fanfix
DS01:/data/local/tmp/fanfix # ./uninstall.sh
Removing fanfix autostart
Removed. Reboot device.
DS01:/data/local/tmp/fanfix # reboot