Topic: Screen is dead

Hi all.
Since i don't live in US i have no valid warranty on my Chumby.
My Chumby is dead. Nothing shows up on the screen when i start it up. The screen gets warm after a while as in normal operation. Are there any hope for my Chumby or is gone for good ? I have opened it up and there are no loose parts on mother or daughterboards. My DHCP server doesn't issue any ip adress to it either so i cannot contact it over ip. I noticed a JTAG port layout on the motherboard. Can it be used someway?
Cheers, Marcus

Re: Screen is dead

Magren wrote:

Hi all.
Since i don't live in US i have no valid warranty on my Chumby.
My Chumby is dead. Nothing shows up on the screen when i start it up. The screen gets warm after a while as in normal operation. Are there any hope for my Chumby or is gone for good ? I have opened it up and there are no loose parts on mother or daughterboards. My DHCP server doesn't issue any ip adress to it either so i cannot contact it over ip. I noticed a JTAG port layout on the motherboard. Can it be used someway?
Cheers, Marcus

Do you have another 12V 1A power supply (maybe from your wireless router) you could use to test the chumby?
Do you have a multi meter you could use to test the power supply?

Re: Screen is dead

Nope it's not the 12V power supply. Tryed with another one without success. Seems like the screen is caputt!

Re: Screen is dead

Same problem here. With my original '08 model. I get a quiet clicking sound if I hold down the power button.  Have tried multiple adaptors. Upon further inspection (relieving the chumby from it's case) I can see the yellow (wi-fi?) light flash upon pressing the power button.

Re: Screen is dead

Please contact Customer Support

Re: Screen is dead

Duane, I spoke with Sam. My warranty is expired, so it didn't sound like much else could be done.
He has shipped me an additional power supply. At one point the chumby came back to life after switching
it out with another supply. But the following day it ceased working again. Is there someone else I should speak too?

Thanks!

7 (edited by kasi 2009-05-23 04:57:58)

Re: Screen is dead

Just wanted to tell you, that you are not alone with this problem. My chumby also doesn't work anymore. I haven't droped it or anything. The support couldn't help me as well. The screen stays dark after turning it on (one can hear the speakers make the usual "on-switch" noise). I have dissasembled the chumby and can see that the wlan LED is blinking blueish (<- is this written correctly?) but can't see the device with my wlan-router sad
Tried different power supplys as well but no succes. Next plan is to check the test point's on the board to se if they have got the voltage they need. maybe one can then tell where the problem is. But I guess it's in one of the covered chips, maybe the chumby was too hot, so there's a little chance that it will work again. I would buy me a new chumby if i knew where the problem is. Up to now, I have no trust in this device sad

EDIT:
just wanted to add:
- the wlan LED of the Chumby is blinking, screen is really off (so no backlight LED problem), and if one put's an usb stick it doesn't seem to get power or isn't recognized (LED of the stick stays dark)

Re: Screen is dead

So, just wanted to add my first measurements:

it seems that the 3.3V regulator doesn't deliver enough power. Testpoint J302 only gives app. 1.8V. The DC-DC Regulator U300 gets it's 5V from the 5V regulator circuit (testpoint J303 shows it correctly and the 5V are also present on Pin 1 of the U300).

So my guess is that either the 3.3V Regulator (U300 is a LM3674) is broken, that some part within the 3.3V circuit is broken or that a device depending on the 3.3V is broken (the load would be to high an the security circuit of U300 limits the output).

I've seen that the 3.3V are needed for the USB controllers and the Main CPU. So there is nothing one can do if these have a problem. So I measured the resistences in the 3.3V regulator circuit. But in difference to the circuit scheme R303 doesn't show the 536kOhm but 84.7k and R305 has no 100k but also app. 85k.

I looked into the datasheet of U300 (or LM3674, which is right in my case, it has "SLTB" on the chip and only the LM3674 and not LM3671 has these) and there you can find that 536k and 100k are really needed if one want's to get 3.3V out of the 5V at the input.


So my question is, do I miss something here or is it really possible that resistors can get broken without doing something to the unit? Maybe Matt can help or say if a similar problem occured with the 3.3V regulator.

Many greetings
Thomas or "kasi"

Re: Screen is dead

No answer from a chumby-tech, but I got a little further. So I'll post it here in case somebody is experiencing the same problems.

At least I can tell that the screen is not broken. As I said the 3.3V circuit seems damaged. So I changed the resistors R303 but after desoldering and measuring they seemed ok. No change in voltage either. Then I changed the regulator U300 (LM3674) and now testpoint J302 gives a little above 4V. It's higher than the 3.3V needed. But at least I can tell that the screen is working in this configuration. After pushing the on/off-button it shows colorful vertical lines across the whole display size.
I searched the internet and found someone with a similar problem:

http://totalueberwachung.de/blog/2008/0 … esurrected

So my next step is to change the P33V_BKUP regulator. The corresponding test point shows little above 7V in my case.

10 (edited by kasi 2009-07-02 06:29:47)

Re: Screen is dead

So a quick update again:

I checked the resistor R303 again, it seemed that my soldering was not succesful. The new regulator LM3674 (or U300 in the scheme) is now delivering 3.3V! The chumby still won't boot, so I also changed the regulator for P33V_BKUP.

AND:

Tadaa, the chumby is working again! It's booting and showing my widgets!!

BUT:

The Bending unit does not work. I have no chance to get into the control panel. (In another thread here it was said, that one has the possibility to get into the control panel by tapping on the screen in the upper left corner, but that doesn't work in my case)
Also the speakers seem to deliver a distorted sound (one widget is a metronome so the click is not the normal click i'm used to).

So again, maybe a chumby tech nows a solution for the bending unit problem?


EDIT: found a workaround that links the bendswitch to nowwhere and uses the easter egg with the upper left corner of the screen for getting into the control panel
see:
http://forum.chumby.com/viewtopic.php?id=3886