REVIEW - Owon SDS7102 - A look at the SDS series from Owon

[lemon]

Author of the article.
https://www.eevblog.com/forum/testgear/review-of-owon-sds7102/?action=dlattach;attach=56620

Snubbers Using Standard Recovery Diodes.

Cheap and slow is not bad. 

Designing R2CD Snubbers Using Standard Recovery Diodes
http://www.intusoft.com/lit/Designing%20R2CD%20Snubbers%20Using%20Standard%20Recovery%20Diodes.pdf

Flash2light thanks for the link. The R2CD is very interesting applying theory and must we give the appropriate attention!

[lemon]

Just TomC has concentrated to psu board, I am thinking to focus to the adapter board.

I don't have the time to make a schematic for all this board but I'll search some dc-dc convertors, difference btw Ver 3.0 and 3.2 and so on.

At the first I am looking the AOZ1094AI dc-dc convertor that produce the 5.5V.
What Owon makes at the the two versions? Look at the attachment photo (left is 3.2, right is 3.0 version).

At the version 3.2 corrects the badly cutting of gnd that previous was made (point 1). Removed the smd capacitor C36 (point 2), adding a second inductor 5.6uH with some smd decoupling capacitors (point 3). The changes was few and very easy to make but is that according to AOZ1094 datasheet?

The next schematic is from datasheet of convertor, a general proposal for 3.3V output. For 5V output the factory suggests L1=5.6uH, Rc=31.6KOhms, Cc=1nF.
For what reason the Owon uses two 5.6uH inductors? For what reason has made mods by hand on version 3.0 with adding a 10uH inductor? Of course was the eliminate the noise but what are they compute.... ?
If you looking more carefully at the schematics, missing some components!
Where the C5=1000pF capacitor that joined the AGND and Enable?
Where is the parallel to diode Rs and Cs components?
At the output the factory suggest two 22uF electrolytic capacitor or some combination : "For lower output ripple voltage across the entire operating temperature range, X5R or X7R dielectric type of ceramic, or other low ESR tantalum or aluminum electrolytic capacitors are recommended to be used as output capacitors."

Have all these in my mind I'll make a check again and I am going to follow the datasheet...

Please, if someone looks the values of smd resistor R18, R19, R20 and R21 on Version 3.2

[TomC]

Author of the article.
https://www.eevblog.com/forum/testgear/review-of-owon-sds7102/?action=dlattach;attach=56620

Snubbers Using Standard Recovery Diodes.

Cheap and slow is not bad. 

Designing R2CD Snubbers Using Standard Recovery Diodes
http://www.intusoft.com/lit/Designing%20R2CD%20Snubbers%20Using%20Standard%20Recovery%20Diodes.pdf

Flash2light, thanks a lot for the link.     

When I was researching the snubber circuits I looked at many articles, but didn't run into anything that mentioned the R2CD developed by the Chinese. I was just guessing at the intent of the designer when I said that the extra resistor "may be an attempt to dampen the ringing frequency with a resistor value that matches the resonant's circuit impedance", luckily, as it turns out, I wasn't too far from the truth.

The R2CD concept is interesting, and certainly reduces component cost while providing a solution that has better performance than an RCD snubber. The article doesn't compare the R2CD EMI performance to a combination of traditional RCD and RC snubbers, so I'm still planning to try that approach during the experimental phase of the project.

Again, thanks a lot for taking the time to share this information with me. It clears up several questions that I had in my mind while trying to understand the PSU circuit.

[TomC]

Just TomC has concentrated to psu board, I am thinking to focus to the adapter board.

I don't have the time to make a schematic for all this board but I'll search some dc-dc convertors, difference btw Ver 3.0 and 3.2 and so on.

At the first I am looking the AOZ1094AI dc-dc convertor that produce the 5.5V.
What Owon makes at the the two versions? Look at the attachment photo (left is 3.2, right is 3.0 version).

At the version 3.2 corrects the badly cutting of gnd that previous was made (point 1). Removed the smd capacitor C36 (point 2), adding a second inductor 5.6uH with some smd decoupling capacitors (point 3). The changes was few and very easy to make but is that according to AOZ1094 datasheet?

The next schematic is from datasheet of convertor, a general proposal for 3.3V output. For 5V output the factory suggests L1=5.6uH, Rc=31.6KOhms, Cc=1nF.
For what reason the Owon uses two 5.6uH inductors? For what reason has made mods by hand on version 3.0 with adding a 10uH inductor? Of course was the eliminate the noise but what are they compute.... ?
If you looking more carefully at the schematics, missing some components!
Where the C5=1000pF capacitor that joined the AGND and Enable?
Where is the parallel to diode Rs and Cs components?
At the output the factory suggest two 22uF electrolytic capacitor or some combination : "For lower output ripple voltage across the entire operating temperature range, X5R or X7R dielectric type of ceramic, or other low ESR tantalum or aluminum electrolytic capacitors are recommended to be used as output capacitors."

Have all these in my mind I'll make a check again and I am going to follow the datasheet...

Please, if someone looks the values of smd resistor R18, R19, R20 and R21 on Version 3.2

That's great Lemon, 

Just like you I'd like to see solutions to the GND noise issue that can be easily and effectively implemented. I suspect that there are quite a few things that can be improved on the Owon design with simple changes to the existing board configuration. This is what I plan to aim for during the experimental phase of my PSU analysis. To discover these possibilities is probably going to take a lot of careful analysis before implementing any changes.

Since you don't have a version 3.2 board and I do, I'm going to try to get the best possible pictures I can get from my board and post them. I'll try to make sure that the component values are readable. Good luck with this project!

[lemon]

Thanks TomC for help, I'll wait for the adaptor board photo of version 3.2.

I'll upload the photo of versions 3.0 too.

[TomC]

Here are some photos of the version 3.2 adapter board and the new PSU board.

[Carrington]

What kind capacitors are they because you have bridged all of them with the first two parallel pins.

http://www.digikey.es/product-search/en/capacitors/capacitor-arrays/131080?k=capacitor

BBAAHHOO very good idea, also add resistors in series would be nice -> rise time, do not run much, that's the idea.
I'm not going to do, because I destroy the board. LOL...

Cheers.

[TomC]

Here is a link to the uncompressed version of the Version 3.2 Adapter and New PSU photos. This link has an expiration date of November 2013. Until then the photos will be available for viewing or download.

http://sdrv.ms/15hxusH

[TomC]

Hi to everyone. My new results. - From the network 18-22 Vpp, battery 12-18 Vpp. Reduced noise from the screen. Added capacitors on the conclusions of the LCD screen ( 0.08 nF which are used in many LCD screens). After this enhancement, there are some distortions on the monitor output.

All power DC-DC original. Added filter and transfer to another place.

BBAAHHOO,
I finally was able to download your file. The noise levels I saw on your photos are very low, better than anything I've seen before. Congratulations!

When you say that there are some distortions with the monitor output, I take it that you mean on something like a TV or computer monitor connected to the VGA output. Not the scope's TFT screen. Let me know if that's not correct.

--To other members that may have had trouble downloading the ZIP file --
I tried to download this file from all 3 computers in our home, none of them was successful. All 3 computers run Windows 7 64bits and the browser is Internet Explorer. I suspect something is incompatible with this browser and the EEVblog website. I finally was able to download the file after installing a Download Manager on one of the computers. The other 2 computers are still unable to download this file.

[Flash2light]

This is ver 3.3

[TomC]

This is ver 3.3

Flash2light,
The component side looks identical to version 3.2. Is there an SMD capacitor underneath C34? That's the only thing Owon had me add to my 3.2 adapter board when I purchased a new PSU board.

I'm also curios about the GND noise level on your scope, on page 92 post 1373 you can see the GND noise level on my scope after I replaced the PSU board and modified the adapter board with an SMD capacitor under C34. It would be very nice if you posted some captures of the GND noise level on your scope for comparison.

[Flash2light]

This shows the noise.

original condition. Not modified.

Ver. sds7102 1319 331

[Flash2light]

without the probe.

[lemon]

Here is a link to the uncompressed version of the Version 3.2 Adapter and New PSU photos. This link has an expiration date of November 2013. Until then the photos will be available for viewing or download.

http://sdrv.ms/1cOVr1M

Please have in mind that it demands account to login.

[lemon]

This is ver 3.3

Flash2light,
The component side looks identical to version 3.2. Is there an SMD capacitor underneath C34? That's the only thing Owon had me add to my 3.2 adapter board when I purchased a new PSU board.

I'm also curios about the GND noise level on your scope, on page 92 post 1373 you can see the GND noise level on my scope after I replaced the PSU board and modified the adapter board with an SMD capacitor under C34. It would be very nice if you posted some captures of the GND noise level on your scope for comparison.

It is really the upper part is identical with paths reference and IC.
It is very strange what this happens to you.
If you remember the member dgmoore78@yahoo.com (post 1331) measures 34mV peak to peak (serial =SN#SDS71021319xxx) also.
The 28mVp of Flash2light or 34mV of dgmoore78@yahoo.com are very well in comparison to yours 70mV.
And something for our knowledge, the version 3.3 was made of 5th November of 2012!

[Carrington]

This shows the noise.

original condition. Not modified.

Ver. sds7102 1319 331

This result is acceptable. I am waiting for both board PSU and DC/DC, last version. Finally, it seems that this is solved, after many months ...

[lemon]

Carrington, thanks for the link with information about capacitor type.

Can you tell us how much was the cost of the two boards and how you paid them?

Of course we'll waiting what versions you'll get up and some photos of course.

For our file upload some photos from adapter version 3.0 (not modification).

[lemon]

...

[Flash2light]

where is the ferrite? I have a ferrite flat cable.
I have not tried its effect.

[lemon]

Some kind of observations with a quick see of adapter version 3.2 vs 3.0

From what I have seen to the adapter version 3.2 it is almost identical the 5.5 and 3.3 dc-dc circuits.
The 3.3 is quite identical, the 5.5 differs only at output that cuts the gnd (version 3.0), also they used at output after the electrolytic capacitor an inductor (version 3.2) with some smd decoupling capacitors (better filtering).

Also the path for -7.6V is the same and has the same decoupling capacitors. Generally the topology and routing of schematics at the two dc-dc converters are 95% same.

The big difference is at TFT Backlight LED power supply. There is an other IC (really can someone find what is S126k) probably a TPS61161A (I don't see clearly) with different power supply. At version 3.0 the output of 5.5 V divides at two with the left one to drive the TFT Backlight Led PS, that isn't happening to version 3.2 that the power supply of TFT BLPS held from 8.4V of PSU board direct.

I am very curious, what adapter version will get up the Carrington...

[lemon]

where is the ferrite? I have a ferrite flat cable.
I have not tried its effect.

I don't know if the Adapter Ver 3.2 had a flat ferrite but mine Ver. 3.0 hadn't.

Please look if there are and others ferrites inside.

[Carrington]

Carrington, thanks for the link with information about capacitor type.

You are wlecome!

Can you tell us how much was the cost of the two boards and how you paid them?

OWON offered me only the PSU and the capacitor ($ 50). I need too the adapter board, since my adapter board is the 3.0.
OWON told me that with the capacitor is sufficient for the version 3.0.  We know that is not true, I tried to explain to them that this is not enough, but no way...
At the end I could get the boards through Aidetek US, this has made all management for me.
And here comes the best: I could pay through PAYPAL, and all cost me only USD45 (postage included). Since the new PSU has been a gift because I buy the oscilloscope to it. I think that after telling the whole "battle" with Owon, it had compassion on me.

Of course we'll waiting what versions you'll get up and some photos of course.

You can count on it. I can not wait, I want to get off this problem. 
I really do not want to know anything more about OWON.

[lemon]

What are you said my friend? 45$ only?   

I have bought the Owon for the Aidetek USA (but is was coming directly from China to my country). I think must to be a contact with them about this. Many many thanks for this information.

Have you tracking information for the arrived day?

[Carrington]

What are you said my friend? 45$ only?   

I have bought the Owon for the Aidetek USA (but is was coming directly from China to my country). I think must to be a contact with them about this. Many many thanks for this information.

What are you waiting?
Mine also came directly from China.

Have you tracking information for the arrived day?

I have no tracking number, because Aidetek has not sent anything yet. He had problems with the manufacturer to get the adapter board. And probably Aidetek not receive it until the next week.

Cheers.

[rf-loop]

The big difference is at TFT Backlight LED power supply. There is an other IC (really can someone find what is S126k) probably a TPS61161A (I don't see clearly) with different power supply.

"This is good candidate for this......but it depends... manufacturing lot... "
 
http://www.gmt.com.tw/product/datasheet/EDS-5126.pdf