What is the right way to fix the step-up inductor whine, as here: https://olimex.wordpress.com/2017/11/03/teres-i-update-first-feedback-from-our-customers ?
I have two screens now (thanks Tsvetan!). The noise only appears with one of them, and only on medium brightness.
This is not so much annoying, but an interesting problem to solve. (I would not want somebody else to do this for me, it has to be DIY.) The blog mentions that one could add a 100uF capacitor. I do not understand the main board schematics, but I have soldering equipment and I am willing to take a risk.
Would it help to replace/add a capacitor or the coil, and if yes, then what exactly needs to be done?
The hardware schematics on github seem a bit outdated. The mainboard revision there is B, and there are visible differences with rev C.
I tried to understand what I can do with the capacitors, and it seems there aren't many options. Take the capacitor right before the step-up inductor (C205, 22uF). It is very small, 1.6mm, and there aren't many replacements of this size. I can find only one of higher capacity (47uF):
https://uk.rs-online.com/web/p/ceramic-multilayer-capacitors/9015332/ (https://uk.rs-online.com/web/p/ceramic-multilayer-capacitors/9015332/)
I can stack two of these on top of each other, this will give me 94uF. I wonder if this makes any sense.
Seems to are C204, C206. You may try to solder two more capacitors 47uF/25V in paralel on them
I took a photo of my board, slightly better quality than those one can find on the internet:
(https://raw.githubusercontent.com/khumarahn/teres1-gentoo/master/main.board.jpeg)
They changed C204 and C206 compared to Rev B. They are not 0805 any more but 1206 (i.e. 2mm vs 3.2mm long), and I do not know how to check the capacity (other than ask here).
Is 25V enough? There is a mention of some 36V in the schematics for rev B, in the list these caps have 50V spec.
I have measured 22uF each and 12V on DCDC output. Refering to display electric absolute ratings: Converter input voltage = 26V, Recomended - min = 5V, Typ: 12V, Max: 21V, so 25V spec. seems to be ok.
Thanks! :-)
I can by these 47uF capacitors:
https://uk.rs-online.com/web/p/ceramic-multilayer-capacitors/7883060/
and replace.
Hi,
I want to bump this topic up as a main question is still not answered completely from Olimex side. I'd like to stop the coil whine by replacing/adding a capacitor on my Teres. In this blog entry: https://olimex.wordpress.com/2018/01/19/teres-i-diy-open-source-hardware-modular-hackers-laptop-update/ Olimex told
Quoteadding bigger capacitor 100 uF in parallel to C204 was solving completely the issue
@Olimex: Could you please elaborate on that capacitor replacement: what is the capacitor voltage and where could we get such capacitors?
Thanks!
Jörg
Just change C206 with 100uF or bigger - this is shown in the picture at the blog post (before the change C204 and C206 were the same).
So search for capacitor 100uF for 16V in 1210 package. The rest of the parameters are irrelevant and personal preference. Of course, you can also use bigger capacitor in slightly bigger package if you have such available.
Thanks!
I received a Teres yesterday and it has significant coil whine - when the brightness is anywhere except minimum or maximum (or off). It looks like C204 & C206 are different sizes so it should be the bigger capacitor and shouldn't have this problem? I'll pop the bottom cover off - hope I don't break any snaps :) - and see if putting some glue on L11 helps. It should be OK to use hot glue right? I don't have any adhesive pads or super glue, although maybe it's better to try them first. The sound is quite loud so I doubt that an adhesive pad alone would absorb all the vibration anyway.
(referring to: https://olimex.wordpress.com/2018/01/19/teres-i-diy-open-source-hardware-modular-hackers-laptop-update/ )
Update: I checked the board & schematic, I think there's a problem with the solder on C204 & C206 where the two close ends have been bridged with solder and are therefore connected in series and having 18 µF combined capacitance, rather than 122 µF as intended. I have contacted support.
Hey,
I received your e-mail and pictures.
The problem is that you still have coil sound... The soldering is fine.
Do not separate the capacitors. It is not a problem that they are connected, this side is common. I attach an excerpt from the board layout – I've outlined the two capacitors and you can see the wire that connects together their VDC side (fat red wire between "1" side).
(https://www.olimex.com/wiki/images/2/2f/Capacitors-common-VDC.jpg)
Best regards,
Lub/OLIMEX
In an attempt to get rid of the noise, I have replaced both C204 and C206 capacitors. The replacement is TDK 47uf https://uk.rs-online.com/web/p/ceramic-multilayer-capacitors/7883060/
This had almost no effect on the noise. Maybe it got a little less loud, but I am not sure. Then I added two more 47uf capacitors, one on top of each. The sound got a bit quieter, but again not significantly.
The whine does not appear with my previous screen, but I have broken it recently.
A picture:
(https://khu.dedyn.io/teres-caps.png)
I fixed the coil with the superglue, and the noise got much quieter, but it is still audible. I am looking for a solution.
Maybe I could replace the coil with another one (if I manage to un-glue it from the board)?
upd: despite the superglue, the whine is back. It has to be fixed before I can use the laptop comfortably.
I tried to find a replacement coil and could not. Where do you source them from? Do you know of anything suitable that would fit the pcb?
Why is there still noise despite the four 47uf capacitors?
I got used to a light laptop with good battery life, which is supposedly repair friendly. It would suck if this problem is not fixable.
I would suggest two things
1. I can send you few coils and few step up converters if you want to solder and see if the problem will still exist
2. Send back the laptop so we can check here
Hi, thanks for the support!
I finally found a 22μH coil that should fit:
https://uk.rs-online.com/web/p/wire-wound-surface-mount-inductors/6920600
I ordered it and will try to replace. (I wish I did not do the superglue, argh!!!...)
On the other hand, if you want to try to understand what is happening, I will be happy to send the laptop to you. (Say, why the noise appears with one screen but not the other.)
send back the laptop so we will see how high is this sound
we experimented a lot on this and some sounds are not possible to be hear by some colleges but other colleges say they hear them so it's very subjective and the people who test the PCBs may have skip some boards with low noise
Good, I will post it to you, hopefully tomorrow. I this the address?
OLIMEX Ltd.
2 Pravda St.,
P.O.Box 237,
Plovdiv 4000 BULGARIA
In my case the sound is very distinct, and it seems to be not only in my imagination. My wife can hear it very well too, despite the new capacitors and the superglue.
Or should it be like this?
Olimex Ltd
Tzvetan Uzunov
2 Pravda Str
Plovdiv 4006
BULGARIA
Olimex people seem extremely busy... ping?
The one at the about page is good enough: https://www.olimex.com/About/
Most delivery companies ignore the P.O. box anyway. It is helpful for our standard e-mail however, since Bulgaria post offices are a bit of a mess and if you don't have P.O. box and you missed the mailmain you might spend a lot of time searching for your mail around the town.
We don't keep close eye on the forums so if you are in a hurry try contacting Tsvetan over info@olimex.com
Good, I have sent it out. Hope it is not lost :-)
Just in case, I included my previous screen. It is shattered, but with it the coil is (and always has been) silent.
My package has been delivered on Friday in the evening, and today (Monday morning) I got an email from Olimex with a tracking number.
That is really fast! Though, I have not heard from Olimex, and I have no idea of what has been happening on their side. I hope that it helped and the source of the whine has been identified. If not, I have now a couple of coils to try as a replacement.
Let us know if the whine persists.
ok :-) I am eager to find out what you have done!
The package quickly arrived, and I am very happy.
Olimex replaced the screen (this is my 3rd!). I could not tell if anything has been done to the mainboard, at least my stacked capacitors and the superglued coil are in place. But the new screen is FULL HD!!! And there is no audible noise now.
Also, they replaced the plastic screen bezel, where I broke a few clips. And included an 8gb flash card with a bootable image.
I am very grateful overall! Will try to understand how to make full hd work under gentoo (somehow the kernel boots into 1366x768).
Hi
LCD is not FHD for sure :) but you can try to run it in HD anyway!
The plastic is same we just placed the wires properly and now the plastic snaps well to the frame, the 8GB Flash SD card is probably forgotten by our people while testing the LCD for noise oh may...
anyway I'm glad we have happy customer
Tsvetan
It boots into full hd with the forgotten 8gb flash card :-) Well, I did not check the pixel dimension, but this is the resolution reported by xrandr. I am relieved that it is not full hd :-) It would have been a bit too much for the small screen, though interesting technically.
Looks like future Teres might have a full hd display?
I took a trace of the VDC18V line with "Power Management Preferences", "On Battery Power", "Reduce backlight brightness" ticked:
(https://war.rui.nz/tmp/2019-07-30.Teres-display-whine.png)
This shows a 4.6 kHz cycle, which I guess is what we're hearing, and 1.74 Vpp with the stock C204 and C206.