Hantek dso2d15 Noise from internal power supply

[iw2evk]

Hi,

somone have tried to modify internal circuit of dso2d15 for reduce the radiofrequency noise irradiated from scope?
I've placed a ferrite sleve on main cord but it's not sufficent for reduce noise.
All around the scope for about 1mt i've strong radio noise on wide spectrum frequencies.

need help , please

Roberto iw2evk

[Aldo22]

I think it's the screen, not the power supply.

[iw2evk]

Nothing to do ?
use a shieded cable for carring out the signal far away to oscilloscope ?

[Aldo22]

Nothing to do ?
use a shieded cable for carring out the signal far away to oscilloscope ?

If you want to shield it for the other devices, a Faraday cage may help. 

If you simply want to see less noise, you can try the following:
- Use a direct, short BNC connection to the DUT whenever possible.
- If you use the probes, use the 1x mode (for the smallest signals anyway).
  The less stuff hanging on the probe (sprung hook, alligator clip) the less “antenna” you have.
- Turn on the bandwidth limiter (BW 20M).
- If it does not trigger cleanly, a trigger holdoff can help (perhaps via PC).
- For repetitive signals, the "Average" acq. mode can help (or a little less the HR mode, for any signal type).

Noise is everywhere. Maybe it's not just coming from the scope?

I don't think the noise is that bad if you help a little.
In the attached image you can see a measurement with
- Probe (1x), sprung hook and alligator clip (i.e. completely normal).
- BW limitation on
- Average Acq. (8x).

This is a very small signal for a measurement with the probes (6.5mVpp) and it still looks reasonable to me.

[Aldo22]

And before you curse the DSO2000:
It has pretty good sensitivity for such a cheap scope.
With a FNIRSI 1014D or 1013D you would see as much as in the attached picture of the signal above (50mV/div).
In this case the noise is not an issue. 

[iw2evk]

Hi,

i've order a double shelded 50 ohm bnc to bnc 1mt cable.

So i suppose can take awey the DUT from scope and reduce noise.

P.s. my test are on radio device, so i suppose i due buy a 50 ohm attenuator for reduce the signal from internal scope generator to input of radio..
Or i can make the attenuator with a kit ?

[Aldo22]

i've order a double shelded 50 ohm bnc to bnc 1mt cable.

So i suppose can take awey the DUT from scope and reduce noise.

I'm not sure if that's a good idea. Maybe you pick up even more noise this way, because the cable is longer?

Can you show a picture/screenshot of what it looks like in your case?

When I place the probe directly on the scope/screen (picture 1), I see a lot of noise.
But in normal operation (picture 2) I don't think the noise is excessive.

The setting in the pictures is: probe 10x, without BW limitation, with HR mode and persistence 1s (100us, 20mV/div).

https://youtu.be/sWPRAKayC3g

[Maximplus]

Many people note that this oscilloscope has a primitive and noisy power supply. Its replacement or additional screening with filtration should help significantly. Unfortunately, the source is 2-channel, there are 5 and 12 V, inconvenient to replace. There is a lot of information on the redesign on youtube, including a video where a classic power supply with linear stabilization was used. Without pulse conversion.

[iw2evk]

Mhh..

can i add some ferrite bead on internal cable and/or ceramic capacitors on pcb  of voltage regolator output ?

I don't have  found imeges on web..

[croma641]

Found this..



This one: exaggerated:



For thermal problems:




'73

[iw2evk]

Ok,

i've see the video.

2 video for add a heathsink to 2 ic (can reduce noise? i don't think this, maybe work more safetly the ic with less heat )

1 video for create a mains insulation with 2 transformer in cascade (mhh.. this can reduce noise from mains, not the producted from internal circuitery)

no video explain if it's possible place ceramic capacitors for drain to groud rf from +5 , +3,3v etc ..

I see in the video 2 flat cable near the  switching power suplly . some ferrite rings on this cables maybe a solution ?

[Aldo22]

I had a look at this with the TinySA.
From my point of view, most of the radiation comes from the screen.
In the first picture, the antenna is directly on the LCD.
In the second picture, the antenna is directly at the back of the housing, where the unshielded PSU “radiates”. But that is significantly less.
Then two more measurements at a distance of 40cm (front/rear).

I don't know if you can do much about it.
Much has already been discussed.
78 pages here: https://www.eevblog.com/forum/testgear/new-hantek-dso2x1x-models/
and 273 pages here: https://4pda.to/forum/index.php?showtopic=1018961

[nokin]

Long time to come back to Hantek related topic 

My experience for this Hantek model are :
1. Noise and noise, lots of noise, no matter how hard you try to improve by any way. It is hardware related due to cheap model.
2. Laggy and laggy

So, change to another brand. Siglent or Rigol. They are more expensive but much better.