PreenFM > preenfm2 and preenfm3
pfm2 with yellow OLED : high frequency solution
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:
--- Quote from: served on February 04, 2019, 07:23:42 PM ---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.
--- End quote ---
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!
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