Pandora screen suddenly changed brightness/contrast

[dimag0g]

Hello,

10 minutes ago I have connected my pandora to the charger, which made it crash (never happened to me before). Upon restart (I had to pull the battery out to switch it off), my screen became much darker than before. I somehow compensated this by setting the LCD gamma to the max, which gives me a similar view of what I had before with default gamma. I'm pretty sure the backlight level is unchanged, the right edge of the screen is well lit when I look at it at a sharp angle.

Are LCD settings stored someplace where they could get corrupted? It has to be somewhere but the firmware, since the screen is dark from the start, before I choose from where to boot. Alternatively, is it possible to increase the gamma even more than the video settings applet allows?

I have already tried to leave the battery out for a minute 30 minutes, which didn't change anything.

 

[EvilDragon]

Have you tried changing the backlight with the brightness keys on the keyboard?


BTW: Instead of pulling the battery, press and hold the Pandora-button while flicking the power switch.


That's also explained in the manual (and quickstart guide), so be sure to read it

 

[dimag0g]

Have you tried changing the backlight with the brightness keys on the keyboard?


BTW: Instead of pulling the battery, press and hold the Pandora-button while flicking the power switch.


That's also explained in the manual (and quickstart guide), so be sure to read it

The power switch didn't do anything, that's why I had to pull the battery out.

Increasing the backlight brightness does work, but it has a different effect: I get too much contrast, and I can see pixel aliasing even when font anti-aliasing is turned on. Also, it will drain the battery.

EDIT: is the LCD interface analog or digital? I wonder if replacing the LCD will do any good.

 

[dimag0g]

I added "op_gamma.sh 5" to my startup script, which helps with both brightness and contrast. However, at this gamma level I can see dark horizontal waves flickering and/or moving across the screen. I guess that's some kind of noise which gets amplified by my gamma setting.

It would be helpful to know what gamma does, exactly. Does it change the way LCD treats the signals it receives, or the signals themselves are modified? And what are those signals, analog or digital?

 

[levi]

AIUI gamma is a purely software colour mapping, working in the digital domain even on an analogue monitor. However, I also believe the Pandora LCD cable carries digital signals (and power), so there's no analogue path to consider.

 

[dimag0g]

AIUI gamma is a purely software colour mapping, working in the digital domain even on an analogue monitor. However, I also believe the Pandora LCD cable carries digital signals (and power), so there's no analogue path to consider.

That's good news, meaning that my issue may be fixed by replacing the LCD (and maybe the cable), if my pandora keeps getting worse.

 

[levi]

A degrading LCD cable is always a possibility that needs to be disproven unfortunately.  First I'd try resetting everything, possibly by doing a reflash though.

 

[dimag0g]

I'm thinking about a reflash, but won't do it right away. Also I strongly believe it won't help, since even the boot menu is affected.

 

[levi]

Hmm, that's true.  Have you checked that the errant capacitor next to the L button hasn't started to come loose?

 

[dimag0g]

Hmm, that's true.  Have you checked that the errant capacitor next to the L button hasn't started to come loose?

Do you mean the coil? I will check it next week when I have time. But again - my brightness alone is ok, but I have to increase my gamma to crazy high values to make the screen look ok.

try "sudo /usr/pandora/scripts/op_gamma.sh 5" to see what I mean.

 

[levi]

Sorry, yeah, inductor/coil not capacitor.  Unfortunately my pandora's out of action after I managed to bend a couple of pins on the LCD cable socket trying to insert cables, so I just need to find my signed board to nick the socket off that (but I'll be damned if I know where I put that board since I moved).

 

[dimag0g]

Hi, I will need more advice on this. I have measured the voltage level on LCD cable pin 36, labelled "5V Power" in pandora hackers manual, and got 3.79V instead of 5. I attached a pic of the pin where I made my measurement, that would be the pin with a black dot next to it.

I also tried to replace LCDs on my unit, and the new LCD shows the same abnormality as the old one, so the issue is clearly in the board.

Can somebody knowledgeable about Pandora schematics tell me if this low voltage is consistent with the issue, and where I should look for the cause?

I have recently met the admin of logic-sunrise.com, who does a lot of repairs on DS and XBOX consoles, and he told me it looked like a capacitor going out of service somewhere, but that was not a proper technical consult of course, just casual chat of two pandora owners =)

 

[matzesu]

Somethimes i get Problems whit the light whyle i put my CC Pandora in USB Host Mode,


Then the LCD Backlight gos to the max brightnes and ditnt be able to change it


Also when i disable USB, somethimes the brightnes cant be changes until i restart the unit..

 

[dimag0g]

Somethimes i get Problems whit the light whyle i put my CC Pandora in USB Host Mode,


Then the LCD Backlight gos to the max brightnes and ditnt be able to change it


Also when i disable USB, somethimes the brightnes cant be changes until i restart the unit..

Just to make it clear, may I repeat that my issue doesn't seem to have anything with backlight brightness. The white color is almost unaffected, while all other colors are shifted towards black (so e.g. a light blue is pretty dark, and deep blue is almost black). Also, my change is permanent, unaffected by restarts.

 

[dimag0g]

At last I have found the issue. It was a faulty TPS60241DGKR chip which converts battery voltage to 5V. I have replaced it with the same chip from the spare board signed by ED I have bought when I met him, so now my pandora is well again.

Below are some pictures for the curious.

The faulty chip taken from the pandora.

The spare chip soldered back to the board. (Don't mind the mad soldering skills, I soldered all pins together on the right side and had to clean up the tin to split the pins)