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

[rf-loop]

Order newest SDS series  PSU, New Adapter board V3.3 (but not newest V4.4) and new FAN and TFT data cable ferrite if there is not allready.

So now the fan cable has a ferrite as well? If so, I might add one to my fan too. Are there any specifications or pictures of the ferrite available?

FAN cable do not need any ferrite.

I recommend "akis" to order also new fan so that he have new FAN for future possible needs becouse it can ship together with other parts now and also becouse he plan change PSU+Adapter and when scope is open, if there is any sign of bad FAN it is clever to change always when scope is in service.

Then I ask he check if TFT data cable if there is ferrite missing (becouse some older scope do not have this) and order also this ferrite from Owon.
TFT data cable need ferrite.

[AndrejaKo]

Thanks for clearing that up rf-loop!

[TomC]

After I change the PSU and the adapter board the scope will be good ? Will I be able to measure low signals, like 100mV ?

Chances are that it will. But as I'm sure you know, there are no absolute warranties on anything!

The new PSU and adapter board have given good results so far for several of our members. I ordered a new PSU from Owon and had good results. My scope is able to measure low level signals, less than 1 gradicule at 50mV/Div full bandwidth and trigger properly on them. When the signal is less than around 35mV the trigger is no longer stable, but this happens anyway, even if I use the short GND clip. So it's no longer due to the GND noise.

[Carrington]

New adapter board version. (not for older scopes)

Older scopes can use V3.3 adapter latest upgraded versions.

But overall this V4.4 tell that Owon have done "hard work" and they have take this case really seriously. But they have talked less and worked more.

I see that keeps the same both connectors.
The version 4.4 still having the R-C network in the back?

[lemon]

Richtek USA has very good support, they provide samples easy. Can you see what marks has?
I don't know what kind is LF1, but you have measured 75mH at your schematics and the Owon's service schematic says 10mH!
Have you looking there?:http://gr.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=120657723

The marking is DP=JOM, so it seems to be the right part, see attachment....

Thanks for info. 

[akis]

I have ordered adapter board and power supply board from China. They charge $60.

I presume it is a straight forward replacement ?

[TomC]

I have ordered adapter board and power supply board from China. They charge $60.

I presume it is a straight forward replacement ?

It should be, the new PSU board and the 3.3 adapter board are the same size as your current boards. Did you include the ferrite for the TFT panel cable on your order? Or does your scope already have it? See attachment. This is also required to get the best GND noise reduction.

[akis]

No it does not, and the lady at the other end of the email told me that I did not need it. I will write to her and ask her to put one in the box.

[TomC]

Richtek USA has very good support, they provide samples easy. Can you see what marks has?
I don't know what kind is LF1, but you have measured 75mH at your schematics and the Owon's service schematic says 10mH!
Have you looking there?:http://gr.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=120657723

The marking is DP=JOM, so it seems to be the right part, see attachment....

Thanks for info. 

You're welcome!

Is this the same markings your samples had?

I sent my order to Digi-Key last night. In addition to the MOSFET and SMD resistors, they also had a 10mH Common Mode Choke that fits and looks exactly like the original PSU choke. It evens has the correct DC resistance. So I'm pretty sure now that 10mH was always the correct value.

[lemon]

No it does not, and the lady at the other end of the email told me that I did not need it. I will write to her and ask her to put one in the box.

Come on Lady, come on lady...what I say to her! This ferrite decrease 10mV the noise about!
If she doesn't send you, remember me to give you an equivalent from farnell.

Richtek USA has very good support, they provide samples easy. Can you see what marks has?
I don't know what kind is LF1, but you have measured 75mH at your schematics and the Owon's service schematic says 10mH!
Have you looking there?:http://gr.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=120657723

The marking is DP=JOM, so it seems to be the right part, see attachment....

Thanks for info. 

You're welcome!

Is this the same markings your samples had?

I sent my order to Digi-Key last night. In addition to the MOSFET and SMD resistors, they also had a 10mH Common Mode Choke that fits and looks exactly like the original PSU choke. It evens has the correct DC resistance. So I'm pretty sure now that 10mH was always the correct value.

Yes, TomC it is exactly the same!
I see, you had a nice end of searching. Very good, your tests will be continue...

[TomC]

Just installed the R7731A and couldn't wait for the rest of the parts to see if it worked. Since there is no Q1 installed, I knew there would have to be gate pulses trying to start up the PSU. So I got some captures of the waveforms at the R7731A gate. These show what happens when the R7731A is trying to start the PSU but the VDD never goes up because there is no Q1.

These captures were done while powering the PSU from my isolated Variac at 120VAC. With the isolated mains I was able to connect the scope's ground to GND-A.

[AndrejaKo]

I have a question about FFT on this scope. I've been doing some captures of signals coming from FM and VHF antennas and I've noticed that when I do FFT of the signal, the greatest peak is not on the expected frequency. For example, I look at the station that's broadcasting at 104 MHz and I see the greatest peak at 104.2 MHz. There seems to be a 200 kHz offset on the entire FM band on results I see.

I exported some data to MATLAB and I can see a consistent offset there too, but it's much smaller. For example, for an FM station that's on 105.2 MHz, I see the greatest peak at around 105.215 MHz.

Any ideas what this could be? Somehow, I expect the stations to have pretty spot-on carrier frequency.

[TomC]

I'm not sure if the FFT should be more accurate, but I think that the 0.2% accuracy that you report is pretty impressive. The manual recommends the rectangle window for best frequency accuracy, I wonder if that would be closer to the MATLAB results since presumably it would be using the same raw data.

[rf-loop]

AFAIK Owon SDS series FFT use 2048 samples. It means theoretical maximum 1024 resolution. Resolution is not accuracy.

True samplerates are (example) 50, 100, 250, 500, 1000MSa/s  and they respond 0 to   25, 50, 125, 250 and 500MHz FFT range. 

If range is example 0 - 125MHz  resolution is around 0.125MHz. with 0-250MHz range resolution is around 0.25MHz. If zoom, true resolution do not change.

[AndrejaKo]

That's what I just realized! I guess I should do a bit more reading and experimenting with FFT. I did FFT on 1k capture in MATLAB and got worse results than on scope and when I did an FFT on 10k capture I got better results, as expected.

Thanks for explaining this!

[TomC]

AFAIK Owon SDS series FFT use 2048 samples. It means theoretical maximum 1024 resolution. Resolution is not accuracy.

True samplerates are (example) 50, 100, 250, 500, 1000MSa/s  and they respond 0 to   25, 50, 125, 250 and 500MHz FFT range. 

If range is example 0 - 125MHz  resolution is around 0.125MHz. with 0-250MHz range resolution is around 0.25MHz. If zoom, true resolution do not change.

That clears it up!
Thanks

[TomC]

Well, the PSU is repaired, however, I have noticed some differences in behavior as opposed to before the accident. In general, the noise generated by the 8.4V is less, however, as far as total noise is concerned there don't seem to be much of a difference. Attached are some captures of the repaired PSU paired to the equivalent captures that I previously posted on post #2072 before the accident. The images on the right are from the repaired PSU.

There is one other thing that is different, the frequency of the oscillator remains constant regardless of the mains voltage. When I tested my new PSU some time ago I had reported that the frequency decreased as the mains voltage increased. I also observed this behavior on my old PSU the day of the accident. Unfortunately, the accident occurred before I had time to capture some images. This makes me wonder if the PWM controller that Owon uses on these PSUs is actually built by Richtek. For all I know it could be a cheaper knockoff built in the mainland.

[pullin-gs]

Odd problems w SDS7102V:
The Vertical Volts/Div knob will sometimes increase when turned clockwise, will sometimes DECREASE when turning same direction.  It is random.  Same for counter-clockwise.  Is random which way the volts/div changes.

The scope will not trigger (very simple test 300khz 1volt sine wave) at times and the only way to correct it is to reboot.

[lemon]

TomC, the comparative results is almost identical, with a little differences (as you told, of course).
OK, we'll wait for the continue... 

@ pullin-gs = this is bad! This happens on both channels or the one specific? How long you have the scope and how to use it until now?

[pullin-gs]

I have owned it for 18 months.
Ch1 and Ch2 both experience the same problem when turning the Volts/Div knob.  This is a new problem which I noticed after it had not been used for the last 6 months.  I pull it out for field work about once every 6 months typically to troubleshoot ANSI standards compliance with telecommunications circuits.

As far as the trigger is concerned, it seems to only happen when setting up "ALT" trigger mode w/both channels and after I have played around with it for a spell.  Seems like a firmware bug?

[Carrington]

Well, the PSU is repaired, however, I have noticed some differences in behavior as opposed to before the accident. In general, the noise generated by the 8.4V is less, however, as far as total noise is concerned there don't seem to be much of a difference. Attached are some captures of the repaired PSU paired to the equivalent captures that I previously posted on post #2072 before the accident. The images on the right are from the repaired PSU.

There is one other thing that is different, the frequency of the oscillator remains constant regardless of the mains voltage. When I tested my new PSU some time ago I had reported that the frequency decreased as the mains voltage increased. I also observed this behavior on my old PSU the day of the accident. Unfortunately, the accident occurred before I had time to capture some images. This makes me wonder if the PWM controller that Owon uses on these PSUs is actually built by Richtek. For all I know it could be a cheaper knockoff built in the mainland.

Congratulations Tom, I'm glad that you could repair it.   

[TomC]

I have owned it for 18 months.
Ch1 and Ch2 both experience the same problem when turning the Volts/Div knob.  This is a new problem which I noticed after it had not been used for the last 6 months.  I pull it out for field work about once every 6 months typically to troubleshoot ANSI standards compliance with telecommunications circuits.

As far as the trigger is concerned, it seems to only happen when setting up "ALT" trigger mode w/both channels and after I have played around with it for a spell.  Seems like a firmware bug?

Your scope is still under Warranty! I would contact the dealer first, and if that don't yield the results you expect contact Owon directly. There are also firmware upgrades recently released, you may want to check those out:
http://www.owon.com.hk/service_s.asp?SortID_1=3

[TomC]

Lemon & Carrington,
Thanks for the encouragement

[TomC]

Today's test involved replacing D5 (1N4007) with a fast recovery rectifier (UF4007). First the R2CD circuit was left intact, next it was changed to a traditional RCD clamp by shorting R4 & R4A. The performance of both configurations was very similar. Surprisingly, the original R2CD circuit with the 1N4007 does a better job of clamping the voltage and dampening oscillations. As far as the overall noise, it doesn't seem to change very much. Given these results, I now think that it's best to leave this circuit unmodified. So I have changed D5 back to a 1N4007 rectifier. The captures show side by side the results for the original R2CD with the 1N4007 (left side) and the RCD clamp with the UF4007 (right side).

[Hydrawerk]

There is a new SDS-E series of Owon scopes. But it is not bettter than the original SDS series.