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

[BBAAHHOO]

[BBAAHHOO]

My rework - transferred power sources 5.5V, 3.3V and screen backlight on separate charges. And added filters on nutrition.
 Very much noisy display. Did it on a separate Board (DC-DC for Led). And moved to the edge of the LCD screen. Now there remain only "digital" noise....I think they signals from the screen. I'll try to play around with resistors.

Sorry for such a English...

[TomC]

My rework - transferred power sources 5.5V, 3.3V and screen backlight on separate charges. And added filters on nutrition.
 Very much noisy display. Did it on a separate Board (DC-DC for Led). And moved to the edge of the LCD screen. Now there remain only "digital" noise....I think they signals from the screen. I'll try to play around with resistors.

Sorry for such a English...

Those are great results! Can you give us some more specifics on the modifications you performed? Like pictures of boards, component values, etc.

[lemon]

TomC, can you measure these smd decoupling capacitors? What value have they?

I don't have the scope apart right now, however, I will be taking it apart when I finish modifications on the old power supply and put it in. I'll make a schematic of the new PSU then and measure all these new components and compare it in detail to rf-loop's DIY. From what I've seen so far, Owon followed rf-loop's version 2b DIY for their new PSU design, so these capacitors are probably what rf-loop recommended, mostly 220nF. Hope you are having fun on your holiday!

OK TomC take your time.
Yes, it is probably they followed the rf-loop's directions.


@ BBAAHHOO = Hi Russia, you had great results!
From what I have undertand you used individual power sources for 5.5V, 3.3V and lcd backlight.
As TomC said, can you give us more information about these mods?

[BBAAHHOO]

[BBAAHHOO]

A strong effect of filters. The LCD screen connected body with the Earth, and transfer the backlight inverter. Ordinary SMD capacitors on 0.1

[BBAAHHOO]

[BBAAHHOO]

[BBAAHHOO]

[BBAAHHOO]

[BBAAHHOO]

[BBAAHHOO]

While I'm at it and will comment ...can anyone else what ideas may lay? 

[TomC]

While I'm at it and will comment ...can anyone else what ideas may lay? 

There have been many ideas posted in this thread, but I haven't seen any with so many extra components as your mods. From what I understand from your schematic, you have added common mode chokes, inductors, and capacitors to filter the noise, but are still using the original DC/DC PWM converters. Is this right?

[BBAAHHOO]

Yes, all native. added filter only. Now only makes noise from power supply (AC-DC), and the visible digital noise (or memory or LCD screen).

[lemon]

Yes TomC, from what I see from the schematics and photos the "BBAAHHOO" uses the original main psu board with a lot of mods. He has removed some dc-dc chips at adapter board, because he gives individual volts to this adapter.

He has applied the most deeper mods that I have seen, but we don't know what versions are the main psu board and adapter board, please BBAAHHOO give us this information.

BBAAHHOO, you have achieve the lowest measurement (I think it is same like rf-loop) at this thread.
Please for comparison reasons, repeat the test of noise ground as decribed at post #1330, page 89 and give us the Vp-p value and the capture.

[Carrington]

Please for comparison reasons, repeat the test of noise ground as decribed at post #1330, page 89 and give us the Vp-p value and the capture.

More about:

The "Mainboard" also have a DC/DC connected to ~5.54V it generate noise that goes to the analog power of the input stage. This DC/DC supply power to the entire DAC. 

Below the shielding metal sheets of the input stage there is a 5V LDO, connected to ~5.54V (i.e Vdo <0.54). And if Owon did not put any filters (F.Bead) in the input of the analog power for the DAC, less to the input of the analog power for the input stage. This LDO is able to reject only some frequencies <1MHz. Similar for the 7905.


Yes, please for comparison reasons, repeat the test of noise ground as decribed at post #1330, page 89 and give us the Vp-p value and the capture.


More:

- To correct variations between channel 1 and 2 in some oscilloscopes Owon add extra resistors there where Owon think.   
- The 5V regulator thermally affects more the channel 1, since it is closer, this explains its greater DC drift. 


Now I do not think Owon would like to save money, rather it seems that, did not even know how to make the oscilloscope. 

Well done Owon... This is not an oscilloscope, is shit. 

[lemon]

Carrington for your observations I'll wait for the rf-loop's answer, becouse he knows this unit very well.
But as we know this oscilloscope has no any noise at front end level.

[Carrington]

Carrington for your observations I'll wait for the rf-loop's answer, becouse he knows this unit very well.
But as we know this oscilloscope has no any noise at front end level.

Lemon, do You think that rf-loop will throw stones at his own roof?

[BBAAHHOO]

#1330, page 89 and give us the Vp-p value and the capture.
Batarey

[BBAAHHOO]

[lemon]

If I see well 28-30mVp-p, many thanks for the captures 

[lemon]

Carrington for your observations I'll wait for the rf-loop's answer, becouse he knows this unit very well.
But as we know this oscilloscope has no any noise at front end level.

Lemon, do You think that rf-loop will throw stones at his own roof?

Carrington I don't know but we can waiting about rf-loop's answering about these issues.

[lemon]

TomC, can you measure these smd decoupling capacitors? What value have they?

I don't have the scope apart right now, however, I will be taking it apart when I finish modifications on the old power supply and put it in. I'll make a schematic of the new PSU then and measure all these new components and compare it in detail to rf-loop's DIY. From what I've seen so far, Owon followed rf-loop's version 2b DIY for their new PSU design, so these capacitors are probably what rf-loop recommended, mostly 220nF. Hope you are having fun on your holiday!

Five more days in this beach with clear water!

[Carrington]

If I see well 28-30mVp-p, many thanks for the captures 

I do not care, but I don't need discuss about what I know.
Besides I already imagine he'll say.

But you notes much difference with the previous result? NO.
Why do you think that not?

If you don't believe me, I don't mind.

Cheers

[lemon]

Carrington because I am not native english speaker, I don't understand your answer.
This is to me? Because my reference for ground noise of 28-30mV was for the BBAAHHOO results!