pfm2 with yellow OLED : high frequency solution

[kreeper_6]

I just built one with a Newhaven Blue OLED and have no noise from what I can hear and see. Is there something that needs to be done for it to manifest?

Last I looked into general OLED issues the Newhaven, Vishay and Raystars were all the same boards, correct?

[served]

I just built one with a Newhaven Blue OLED and have no noise from what I can hear and see. Is there something that needs to be done for it to manifest?

Last I looked into general OLED issues the Newhaven, Vishay and Raystars were all the same boards, correct?

Its very high pitch noise. So it depends on your hearing. Best would be if you look at it by running Preen into your soundcard and looking at the spectrum graph. It should present a peak in 15-16kHz region.
The loudness varies on different things. So you might be lucky or you might not hear it. The boards seem to be the same, but components on the boards vari.

[kreeper_6]

Its very high pitch noise. So it depends on your hearing. Best would be if you look at it by running Preen into your soundcard and looking at the spectrum graph. It should present a peak in 15-16kHz region.
The loudness varies on different things. So you might be lucky or you might not hear it. The boards seem to be the same, but components on the boards vari.

I think it would help if those with issues referenced the part number of the OLED installed. I will be trying out various OLEDs available to me (Newhaven/Vishay) and post my results.

Newhaven Blue NHD-0420DZW-AB5

[clément]

I posted mine somewhere in the forum, other members did.
But I'm so glad to see your results! You are not using any shielding like it's mentioned in this topic?

[kreeper_6]

I posted mine somewhere in the forum, other members did.
But I'm so glad to see your results! You are not using any shielding like it's mentioned in this topic?

No shielding and using the latest PCB. I didn't even know there were issues with OLED as it seemed to be the standard choice for the preenfm.

[served]

I can confirm that Blue OLED screen from Newheaven does work. No whining noise.
But it has issues with the pixcels brightness and it sometimes skips as the signal level is probably on the low limit.

[maximee]

Hi all, thanks for sharing your recent discoveries about the different OLED types.

I'm eager to try a different display myself, because I couldn't sufficiently tame the noise issue.
I was going to try to replace the inductor with a shielded one, but from what I see the results on the spectrum posted above look much nicer.

Too bad those OLEDs aren't exactly cheap. Would love to keep my PreenFM yellow – will post back when/if I try it with the NHD-0420DZW-AY5.

[served]

Hello,

I can confirm that the whining noise that you can hear from the screen or in the audio path is due to the Inductor type.
I have swapped the Bluse screen inductor to a different type and it started to make loud audiable noise.
Same test in the Yellow screen. And the symptoms are the same.

Keep your eye on the heat when using different colours. Blue screen for example draws a lot more current than the Yellow one. So your voltage regulators will go a lot hotter.

[kreeper_6]

I can confirm that Blue OLED screen from Newheaven does work. No whining noise.
But it has issues with the pixcels brightness and it sometimes skips as the signal level is probably on the low limit.

Do you have a resistor in the OLED position? At first I had some pixel brightness differences across the display until I pulled the resistor and put in a wire jumper.

Hello,

I can confirm that the whining noise that you can hear from the screen or in the audio path is due to the Inductor type.
I have swapped the Bluse screen inductor to a different type and it started to make loud audiable noise.
Same test in the Yellow screen. And the symptoms are the same.

Keep your eye on the heat when using different colours. Blue screen for example draws a lot more current than the Yellow one. So your voltage regulators will go a lot hotter.

I have marked down some shielded inductors for order to test on a Newhaven Green NHD-0420DZW-AG5 that has the noise problem @ 13.8k; It has a different component configuration to the Blue display. I had ordered a blue Vishay Blue O020N004ABPP5N0000 but the display has some character line issue, the board is exactly the same as the newhaven including the components so I'm not sure if it could be the controller or possibly just defect. I may order a different color Vishay to test again; It does not suffer from the noise issue as it has what I assume is a shielded inductor that is the same as on the newhaven Blue.

I'll take note on the heat of the regulator and maybe swap it out for a switching regulator.

Newhaven Green NHD-0420DZW-AG5






Vishay Blue O020N004ABPP5N0000

[served]

Good points! I will check that resistor!

Butw it would be interesting to know what inductor is on the Blue screen.
I could not find it anywhere. Not even similar one.

If you need inductor for the other colours read this thread:
http://ixox.fr/forum/index.php?topic=69470.0

[kreeper_6]

I swapped out the inductor with a few others to no avail. One did manage to shave off the peak from the noise spike but all 3 had introduced audible noise emanating from the inductor itself.

It is possibly the power converter that needs to be replaced. I'm not sure of the difference between the two power sections on the Green vs the Blue as they both look to output 5v. The blue uses a TPS61040DBVR from what I can tell from the chip marking and the datasheet suggests a Sumida CDRH3D16-100 inductor that looks similar to what is on board. I haven't been able to track down the Green converter part number or spec but I might just swap it blind. The converter on the blue boasts a switching frequency of up to 1mhz and I'd guess that the converter on the green/Yellow and Red vishay has a switching frequency in the audible range.

I may have to contact newhaven to get the scoop on what is going on.

Coilcraft LPS4018-334MRC



Bourns SRR4528A-331M



Bourns SRR4028-331Y

[served]

I have contacted newheaven and Raystar.
They are extremely secretive about the design and they dont acknowledge the noise issue.
After tens of emails I got only one fact that I could use. It was about the inductor specs that are used. And they didnt want to comment anything else.

We decided to take a more simple and easier path.
I have re-designed PreenFM PCB to make this issue disappear. PCB Drawings will be released in nearfuture. (a month or so)
Still need to test and measure and maybe make some corrections.

[kreeper_6]

I have contacted newheaven and Raystar.
They are extremely secretive about the design and they dont acknowledge the noise issue.
After tens of emails I got only one fact that I could use. It was about the inductor specs that are used. And they didnt want to comment anything else.

We decided to take a more simple and easier path.
I have re-designed PreenFM PCB to make this issue disappear. PCB Drawings will be released in nearfuture. (a month or so)
Still need to test and measure and maybe make some corrections.

Newhaven never got back to me as expected. How is that new PCB coming?

[served]

Done and working.
I am currently a bit struggling with semimodular part of the project design.
But in few weeks I should have that ready.

[Paulus]

Hello all, just a quick message to mention that I finally did this mod after a few years with the high pitch noise.
I'm pretty sensitive to high frequencies and this has been bother me a lot lately.

For me the aluminium sheets mod did not decrease the noise enough ( about 15-20db) and I could still hear it. Maybe my kitchen aluminium was not of the best quality (recycled I guess), so I decided to use two layers of 1mm thick aluminium plate. I also had to wiggle it a bit until it would hit the perfect spot and the fit is pretty tight (the screen is slightly lifted).

I now have a 30db decrease and I was able to hit -100db on the 13khz peak. This is pretty good!

thanks for the tips!