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

[lemon]

They changed all topology, routing and IC's, completely.
It is interesting why they don't keep the compatibility with the older versions. Maybe have changed and z-plate, rf-loop?

[TomC]

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.

Is this in production? Or is this preliminary info you got?

[rf-loop]

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.

Is this in production? Or is this preliminary info you got?

In normal production.

[rf-loop]

They changed all topology, routing and IC's, completely.
It is interesting why they don't keep the compatibility with the older versions. Maybe have changed and z-plate, rf-loop?

Afaik it is functionally compatible, but TFT data cable is small amount too short in older models for this.
I have not time now to check if it need small mod for Z-plate corner or if can not?

[TomC]

Good news!

I just received R7731A samples from Richtek. Very nice of them to provide samples even though I explained that this wasn't for a new project, but for an existing PSU with a defective R7731A which I couldn't obtain locally.

I can get the MOSFET and the SMD resistors from Digi-Key, which I'm going to order soon.

The only remaining problem is the Common Mode Choke (LF1). I measured it's inductance in circuit in the past at it was 75mH. After I took it of the PCB, one side measured 100mH and the other less than 1mH. However, the ohms measurements proved that both sides have been damaged. I can't find a replacement of either value (75mH or 100mH) that will fit in the existing PC board holes.

So I took it apart to see if I could rewind it. It has 161 turns per coil, and the wire is 160" long. With it unwound the wire measures about 2.5 ohms (while it still was in the coil both sides measured quite a bit less than this due to internal shorts). The gauge of the wire seems to be Metric 2.0. The closest thing I have is AWG 30 which is thicker, about 1.5 ohms for 160". So I'm considering using this even though I'll probably end up with quite a bit less inductance. The only other alternative that I have so far is to use a toroidal choke salvaged from a PC PSU. It fits in the space available but has different inductance (about 1mH).

[akis]

Regarding my noise problem(s) Owon China have replied to me saying

1) there is a new "board" that costs $10 + $50 for shipping....
2) Meantime,kindly noted the new board only can reduce noise.

Can someone please explain to me?

(1) I thought that I need to replace two boards, something called the "PSU" board and another called the "adapter" board. Why are they talking only about one board?

(2) Why are they saying "only can reduced noise" ? Do they mean "cannot eliminate noise" ?

[lemon]

Good news!

I just received R7731A samples from Richtek. Very nice of them to provide samples even though I explained that this wasn't for a new project, but for an existing PSU with a defective R7731A which I couldn't obtain locally.

I can get the MOSFET and the SMD resistors from Digi-Key, which I'm going to order soon.

The only remaining problem is the Common Mode Choke (LF1). I measured it's inductance in circuit in the past at it was 75mH. After I took it of the PCB, one side measured 100mH and the other less than 1mH. However, the ohms measurements proved that both sides have been damaged. I can't find a replacement of either value (75mH or 100mH) that will fit in the existing PC board holes.

So I took it apart to see if I could rewind it. It has 161 turns per coil, and the wire is 160" long. With it unwound the wire measures about 2.5 ohms (while it still was in the coil both sides measured quite a bit less than this due to internal shorts). The gauge of the wire seems to be Metric 2.0. The closest thing I have is AWG 30 which is thicker, about 1.5 ohms for 160". So I'm considering using this even though I'll probably end up with quite a bit less inductance. The only other alternative that I have so far is to use a toroidal choke salvaged from a PC PSU. It fits in the space available but has different inductance (about 1mH).

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

[lemon]

Regarding my noise problem(s) Owon China have replied to me saying

1) there is a new "board" that costs $10 + $50 for shipping....
2) Meantime,kindly noted the new board only can reduce noise.

Can someone please explain to me?

(1) I thought that I need to replace two boards, something called the "PSU" board and another called the "adapter" board. Why are they talking only about one board?

(2) Why are they saying "only can reduced noise" ? Do they mean "cannot eliminate noise" ?

Probably, they meant the PSU board but you must to clear it before.
Can you remember me, have you open the scope before? If yes, what psu and adapter versions have you?

If you don't know what kind of version you have, it is very difficult to take right decision for what to do.

[akis]

OK so I need to open up the scope and read two version numbers, adapter board and PSU?

My scope serial number is SDS71021211675 - I bought it in summer 2012 - I presume it has the "bad" PSU and adapter board. I am going to open it now.

[rf-loop]

Regarding my noise problem(s) Owon China have replied to me saying

1) there is a new "board" that costs $10 + $50 for shipping....
2) Meantime,kindly noted the new board only can reduce noise.

Can someone please explain to me?

(1) I thought that I need to replace two boards, something called the "PSU" board and another called the "adapter" board. Why are they talking only about one board?

(2) Why are they saying "only can reduced noise" ? Do they mean "cannot eliminate noise" ?

Probably, they meant the PSU board but you must to clear it before.
Can you remember me, have you open the scope before? If yes, what psu and adapter versions have you?

If you don't know what kind of version you have, it is very difficult to take right decision for what to do.

It reduce noise, it do not remove all noise. No one can remove all  noise.

I will recommend change both, result is better.

PSU (new version have some amount less noise)

Adapter board version V3.3 and  latest sub version.   Then note: if you do not have right soldering tools: Ask TFT backlight (it have two pin but 4 point surface mount) connector is already assembled on the board!

(most new V4.4 adapter board do not fit directly to older versions.)


(psu is not expensive and with same shipping price I think)

Also, if scope is without TFT data cable ferrite it is best to ask also it included in same shipping.

[rf-loop]

OK so I need to open up the scope and read two version numbers, adapter board and PSU?

My scope serial number is SDS71021211675 - I bought it in summer 2012 - I presume it has the "bad" PSU and adapter board. I am going to open it now.

Owon need only your serial number.

You need new version PSU + you need version V3.3 Adapter board.

If you order from Owon and with this shipping price

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.

[akis]

OK I will now email them exactly as you wrote it

"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."

[rf-loop]

OK I will now email them exactly as you wrote it

"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."

Do you know there is not this ferrite?
If there is not, you need it, if there is you do not need it.
You can see it after you open it. (this is missing from some older scopes but I do not know your scope)

[akis]

OK I am trying to open it now.

I have taken out the battery. It reads:
Li Polymer.
Cell: 4669120 / 4000 mAh/3.7V
Pack: 2S2P 7.4V / 8000 mAh

So this battery contains 4 cells of 3.7V each, put in series to give 7.4V and in parallel to give 2*4000mAh = 8000 mAh.

Or have they simply put two cells in series and then claim 8000 mAh ?

[rf-loop]

OK I am trying to open it now.

I have taken out the battery. It reads:
Li Polymer.
Cell: 4669120 / 4000 mAh/3.7V
Pack: 2S2P 7.4V / 8000 mAh

So this battery contains 4 cells of 3.7V each, put in series to give 7.4V and in parallel to give 2*4000mAh = 8000 mAh.

Or have they simply put two cells in series and then claim 8000 mAh ?

It is 7.4V 8000mAh  if there is two 3.7V 4000mAh cell series it is 7.4V 4000mAh.
There is "2 series, 2 parallel = 4 cells + of course control electronics also inside package.
Manufacturer is (typically) Hangzhou Wanma.

[Filip Jukic]

Yes i see 0Hz spike, it is wierd..... i think red marker (1) on the left of the screen should be referent not center of the screen, but it is not big problem, before doing FFT i just need to put CH to the center. Am I right?

Myself, I either do that or ignore the spike.

I have one more question about FFT.
When i change horizontal scale in Hz, horizontal scale in seconds (of the wave) is changing too. The same is happening with Vrms scale, but not with dB scale. Hope you understand.
This is stupid, i want to change X and Y scale of FFT not scale of the wave !!

[akis]

There is "2 series, 2 parallel = 4 cells + of course control electronics also inside package.
Manufacturer is (typically) Hangzhou Wanma.

Ahh that is excellent. You see, if you go on ebay, there are dozens of Chinese LiOn battery packs, light blue in colour usually, claiming to be 12.6V/9600mAh when it fact they have 3 cells of 3.7V/3200mAh inside. That is thieving.

By the way, could you please point me to the message which shows how to open up the Owon ? I have taken 4 screws out the back but the back cover will not budge.

[TomC]

Yes i see 0Hz spike, it is wierd..... i think red marker (1) on the left of the screen should be referent not center of the screen, but it is not big problem, before doing FFT i just need to put CH to the center. Am I right?

Myself, I either do that or ignore the spike.

I have one more question about FFT.
When i change horizontal scale in Hz, horizontal scale in seconds (of the wave) is changing too. The same is happening with Vrms scale, but not with dB scale. Hope you understand.
This is stupid, i want to change X and Y scale of FFT not scale of the wave !!

Yes, the two are connected, so it's somewhat inconvenient. I'm not sure if this is implemented the same on DSOs from other manufacturers. It would be nice to know if someone has the answer. But this is not a malfunction on your scope, mine works the same way.

[TomC]

There is "2 series, 2 parallel = 4 cells + of course control electronics also inside package.
Manufacturer is (typically) Hangzhou Wanma.

Ahh that is excellent. You see, if you go on ebay, there are dozens of Chinese LiOn battery packs, light blue in colour usually, claiming to be 12.6V/9600mAh when it fact they have 3 cells of 3.7V/3200mAh inside. That is thieving.

By the way, could you please point me to the message which shows how to open up the Owon ? I have taken 4 screws out the back but the back cover will not budge.

Check this video: Just be careful with the Pwr button, you have to push it down while opening the top half of the cabinet.

[akis]

OK thanks for the video. I have taken these pictures

[lemon]

I see you have proceed!
Your PSU version is the same like Adrejanko, very bad version!
Your adapter version is 3.0 like me.

It is better to change both of them, as rf-loop told. I am very sure that you haven't the flat ferrite on tft cable, too.
Send an email to Owon for these 3 items and ask a better price.

[akis]

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

[AndrejaKo]

Yes i see 0Hz spike, it is wierd..... i think red marker (1) on the left of the screen should be referent not center of the screen, but it is not big problem, before doing FFT i just need to put CH to the center. Am I right?

Myself, I either do that or ignore the spike.

I have one more question about FFT.
When i change horizontal scale in Hz, horizontal scale in seconds (of the wave) is changing too. The same is happening with Vrms scale, but not with dB scale. Hope you understand.
This is stupid, i want to change X and Y scale of FFT not scale of the wave !!

Yeah, that's how it works. I wrote a long post refuting your claim that timebase setting is not relevant to FFT setting with measurement examples, but my computer ate it and I of course did not back up the data. Timebase is affected in dB mode as well, but it may not be as obvious. For example, set your CH1 to 10 ns/div and go to FFT. On my scope, it goes to 400 MHz/div. Once I mode it to say 5 kHz/div and exit FFT mode, scope is in 1 ms/div. Also sometimes, the timebase will change but the timebase indicator will not change. This almost always happens when doing self-calibration, but I think it happened a few times to me with FFT mode as well.

You can't actually do what you want, since FFT data is (obviously) just calculated from the samples taken from the X and Y waves. In FFT mode with Vrms set, you're actually directly controlling the volts/divs scale directly and FFT is calculated by the method described in the manual. Scope takes 2048 samples from the channel, calculates FFT using that samples and puts it into 1024 bins. You can either set the channel and go to FFT mode, or you can set the channel indirectly in the FFT mode.

I'm not sure what they're doing in dB mode for voltage ranges...

[AndrejaKo]

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?

[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.

I had checked Mouser before, the US site, but they don't have something that will fit, at least in the 75mH-100mH. Like you said, the Service Manual Schematic says 10mH. I measured 75mH in circuit, but in circuit measurements can easily be incorrect.

I rewound one of the choke's coil with AWG 30 but could only fit 70 turns. When I checked the inductance it was slightly less than 1mH. This reading may not have been very accurate because one of the core's C halves broke in two. I was able to put everything together anyway, but the junction where the core broke may be causing a reduction in the inductance, however, I doubt it would be 30mH less for example. Anyway, I'm thinking now that perhaps the real value may be 10mH like the Service Manual says. So I'm going to look for some chokes with that value. In any case, this part is not essential for the PSU's operation, it's only there so that the product can pass the EMI requirements as far as interference with other equipment connected to the same AC source.