I done one measurement of 10MHz at 40mV output. Two large ferrites with each of them with one looped cable inside.
Yes there is an improvement but without right triggering. The reason of this is that I have removed all the mods to the Led Back-light Circuit and for this time the gnd-noise has increased.Nice!
I think it will get even better when you put the mods back in.
We don't know how "crappy" is the TDS Series, there is no any review about this only photos and some technical characteristics.
Oh, I am not very familiar with these Owon bugs, but one thing is clear. I am never gonna buy any Owon scope. Even their TDS series is crap when compared to GW Instek, Rigol, Siglent or Agilent. (Unless you really need a touch screen. )
Owon seems to follow the directions of manufacturer, there are two decoupling capacitors C40, C41 at the input supply , there is an inductor of 10uH between input and LX and so on.
The only that missing is the 1uF output capacitor that there is a position for that but it is empty The output voltage of this IC measured at position of C35 at 8.765Vrms with the Backlight to 0%.
22 Feb 2013, 18:54 Post subject:
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This old information is obsolete for 2012 and 2013 versions
2011 end, 2012 whole adapter board have been under development and it have changed many times! Sometimes less, sometimes radically.
Also in adapter board TFT backlight LED control have changed (many times) and freq are different. Also components are different. But still principle is same.
Last versions this circuit produce lot of noise and it need also modify on the aadapter board for less noise. (+ some other modifications for reducing GND noise.)
Backligt LED's current is important parameter and it need follow Innolux datasheet!
Why I feel you love to troll around ? Like jumping in a thread like this where owners are discussing "specific" scope model and bashing it like there is no tomorrow ? And I noticed you did that at Rigol thread too.
And its funny the brand GW Instek always pop out at this typical post of yours.
Hydrawerk,
I'm just trying to understand your reasoning!
Do you own a scope? If so, how did you decide it was the right one for you?
If so, how did you decide it was the right one for you?
Hydrawerk,
I'm just trying to understand your reasoning!
Do you own a scope? If so, how did you decide it was the right one for you?Yes, a DSOX2002A. https://www.eevblog.com/forum/reviews/my-new-toy-%29-agilent-dsox2002a-sex-on-a-stick!/msg216361/#msg216361If so, how did you decide it was the right one for you?It is rather a long story... My friend had a bad experience with his Rigol. https://www.youtube.com/user/BigOne332137/search?query=rigol I wanted a scope with a free waveform generator. I knew many Agilent scopes from my university. They were easy to operate and very responsive. I was considering even the GDS-2000A, but I found out, that its Trig Out is weird.
rf-loop very interesting information.
Yes, we are familiar with the changes that have done to Version 3.2 or 3.3, just this is like exercise to this circuit and how we can to improve with its limit.
I believe that I have followed your thought with these mods.
There are decoupling capacitors at the input and the output.
Here the tests before and after mods. The waveforms captures are with the tip of probe over the component without gnd connected anywhere.
All the spikes has gone. It is very interesting how eliminated all the spikes at the output.
Attachment files
mods.png = the mods on this area
L2.png = measurement over the L2 inductor
D12.png = measurement over the diode
IC.png= measurement over the EDS-5126
Output.png = measurement at the C35 position
In some versions output capacitor is also behind long PCB trace and this is totally wrong and also as in many cases, there have been even crap electrolytic only alone, and this is just like nothing with these risetimes and frequencies. Just becouse they follow only this kind of datasheed principled schematics. (and same problem in some other circuits)
In this kind of SMPS, both current loops need be low inductance and if want avoid common mode noise in GND these current loops over GND need isolate from common GND area using "single point" connection so that this RF current do not fllood around ground. This PCB "topology" is terrible if think EMI. They have tried break all possible rules what can break if want design low EMI circuit.
Here the tests before and after mods. The waveforms captures are with the tip of probe over the component without gnd connected anywhere.
This circuit need good bypass capacitor in its input and its output. (there is not)
In some versions output capacitor is also behind long PCB trace and this is totally wrong and also as in many cases, there have been even crap electrolytic only alone, and this is just like nothing with these risetimes and frequencies. Just becouse they follow only this kind of datasheed principled schematics. (and same problem in some other circuits)
In this kind of SMPS, both current loops need be low inductance and if want avoid common mode noise in GND these current loops over GND need isolate from common GND area using "single point" connection so that this RF current do not fllood around ground. This PCB "topology" is terrible if think EMI. They have tried break all possible rules what can break if want design low EMI circuit.
More improvements. Now most of the noise comes from the local FM station 106.5MHz (previously I could not see this, because the SDS noise covered it). I have to paint the wall with conductive paint too...
Owon, takes note!
If I remember correctly, there was one theory that mentioned noise on the sense pin of MC34063 is the reason for duty cycle change. If I understand how this works correctly, decreasing resistors on the pin should increase noise immunity, right? My PSU has a 9.07 kiloohm resistor from the pin to the ground and 1.794 kiloohm resistor from -7.6 V to sense pin. This should give nominal voltage of -7.569 V and current through the resistors of around 700 microamperes, if I'm right. I'll try with combination of 1.1k and 5.6k and see how that goes.
TomC, if you see at the Carrington's attachment photo the two boards are new versions (and the show is that the new PSU board haven't any mark again!)
AndrejaKo, I'll waiting for your results and observations, start at the first with the LED Backlight mods.
Thanks guys for encourage to my trials.
Carrington, your news is marvelous.
I am looking here to find Kontakt 35 or similar product.
When you have time, don't forget to upload the measurements after the apply of shielding.