[SOLVED] Backlight always on when screen is off - Xiaomi Redmi 4a Guides, News, & Discussion

Hi
I have an issue with my small redmi 4a.
Some times ago the phone felt down and the lcd broke and the backight started to stay always on if screen is off.
So I decided to change the lcd and I bought one with the whole frame.
Now the lcd glass is perfect, but I still get the backlight always on when screen is off, so it seems something in the boards or in the connections between board and the lcd.
What can I check more?
Thanks

Try a hard reset.
Make sure no ribbon cable micro connector contacts were damaged during the repair. That all grounds and connectors are connected. Sometimes these connections are made by direct physical contact between subassemblies; eyeball it carefully for contact pads.
Check the mobo very carefully for damage or debris. A PC trace or component solder joint maybe broken or less likely shorted by debris.
If it's a trace or surface mount solder jiont it may be very hard to find if at all.
IDing where the backlight driver is/where it gets its high/low signal from the mobo would help you narrow down the area hopefully.
It's also possible the backlight driver control circuit was blown.

Thanks for the reply @blackhawk
The issue was there previously to my repair, so probably happened when the phone felt down and the screen broke.
There are two boards, one in the upper side and one in the bottom side of the phone.
Do you think there is something wrong in the main (upper) board or the bottom one?
Just to concentrate on one...
Thanks again!

Really strange...
It seems not to be an hw issue.
I jest flashed, with Miflash, MIUI 9.2 Global and now the backlight does not show anymore.
Previously I was on Resurrection Remix (8.6.4) Android 10 and tried also the Android 9 version....
So I decided to try again to install RR with Android 10 and now all works fine.
Probably the MIUI installation via MiFlash repair something went wrong previously...

Excellent!
That's hella better than trying to track down a PCB issue.
Didn't know your were mucking with the firmware, lol the usual suspect
Put a good case on the puppy if you can... as you see now how convoluted it can get.

Related

screen just shows lines

anyone know how/where to get an xda mini II repaired? i'm in italy, but i can careless where it has to go. I'm at the point where i would rather just sell the device for it's workable parts (if there are any)...Today the screen has done a myraid of interesting things...anywhere from blank to thousands of vertical lines....ugh...
ohh yeah...warranty is void....or is time to just move on?
ok...no answers so i thought i would add some images ...anyone seen this before?
Mate i had a similar **** up a while back ...I did a HR and it worked fine..for me it was caused by a Overclocking software [Dnt want to Name it ]
If this dnt work try the Batt out and back in trick
Call ur Local service Center...
mine looks exactly teh same! but it happened after i tried to replace my housing, i screwed up the little gold prongs where the ribbon connector from the lcd plugs in...****! any ideas on how to fix? im the us so service center isnt really an option, and id ont want to send it off.
hi i had the same problem with my magicians, after i changed the housing. i found the problem with my device was that i had not plugged the screen back in properly. all i did was to ensure that it was pushed in properly before i clipped it back in
Menappi -
I had the exact same issue. I reopened the casing WITHOUT disconnecting any cables. I flipped the screen's ribbon black lock up, while maintaining pressure on the ribbon so that it does not pop out. When the black lock lifted, the preasure of my finger moved the ribbon further in . I pushed the black lock down, reassembled the device and ... PRESTO!! the screen works perfectly... and chumps on the bard advised to buy a new screen!!
Good luck
Hi All,
seems, you have problem somewhere in display connector. However, sometimes I see similar picture on physically broken displays, let's imagine, you were careful ad didn't use a hammer during housing replacement.
There are two possibilities: at first - try to remove and re-insert display cable (I hope, you know. how brown lock works). If there is no success - try again. At second - some wire on flat cable may be damaged. Sometimes, good technician with soldering iron can fix it, sometimes not. And if you used force, removing cable, board connector may be damaged too. However, only the experienced man can find it easily.
So, try to carefuly re-insert display cable. Try several times. If you are unsuccessful, you, for sure, need an experienced technician to fix your device.
I hope, you are not enough mad to send device for repair to Russia

Possible new cause for white screen and d-pad failures

Hello
I have managed to come to the conclusion that the original cause for the d-pad failures is NOT the loose connector as described before. this connector is in fact surprisingly sturdy.
the problem lies with the little black IC on the keypad membrane.
i am taking my hermes tomorrow to my friends' phone repair shop and he is going to heat the IC up for me and allow it to reseat.
i shall report back tomorrow.
------------------------
just in case your wondering, i came to this conclusion by purposefully 'un seating' that IC and lo and behold, intermittent white screen and d-pad failures. however if i applied pressure to the IC it allowed it to make contact and it worked again, let go and white again.
many thanks
It will be interesting to hear the results on this BUT -
I'm not certain I agree with your methodology here though. I am not surprised that deliberately un-seating the IC causes a white screen! In all probability removal of any number of components will cause a white screen! AND of course heat gunning it again to re-establish it's connections will make it work again!
Unfortunately this does not prove to me at least that the IC is the problem for most people. If I remove a capacitor from my TV and the picture goes, I cannot conclude that everyones picture problems are related to that capacitor. The D'pad connection though it may appear sturdy has a set of very fine connections and it only takes one to be fractionally bent or oxidised for you to get the whitescreen or indeed a poor connection of any component or connection.
However the IC was reported on in the loooong white screen thread where some folk found that placing padding on the IC surface or squeezing it would correct the white screen and thereby concluded that it was an IC connection fault.
Of course the problem is IMHO that there are several possible causes and any individual person can have one or a combination of things causing the white screen. So far we have as possible causes:
D/Pad connector (must be seated firmly and FLAT but neither over tightened nor too loose. The pins may also get slighly bent or oxidised so cleaning them or fractionaly bending them may work
The D/Pad IC may have poor contacts.
The LCD Flex cable may have cracks (but less likely in my view)
Some have reported capacitor faults (possibly poor connections or degradation with heating or current draw) on both D/Pad and M/board. These faults may be related to the whitescreen only appearing after 10 or so minutes of use and recovery after switching off for a while.
Heating up - in some cases the whitescreen only appears when the phone is warm/hot. This may be caused by expansion of the multi-layered board causing poor contacts / or possibly components not performing correctly due to heat or current draw.
Often some of these whitescreens can be made to disappear by putting pressure on certain components / connections or even in some cases by squeezing the phone casing near the D'pad area. So all in all it is likely to be poor contact somewhere, it's just that it can be in several possible locations - including but not exclusively the D-Pad IC.
Mike
first of all, can i just say what an honour it is to have you comment on one of my threads!
second of all, i am only trying this as a last resort to revive my hermes before i jump ship to the raphael/diamond. or unless i decided to buy a new keypad PCB for it in the hope it will fix it!
i shall report back as soon as ive been down to the shop
many thanks
hi there
i had the white screen initially and although intermittent was useable, then, progressively got worse. countless reseats of the cable, time and time again, including put 'foam' in the places indicated then i did indeed notice in that post about the ic
so, i decided to experiment with the IC. first two layers of paper on top, made some difference in that i had to apply less pressure to get it to work, and then i though, id heat it up slightly using a hairdryer (only thing i had to hand!) and a nozzle made out of a drinks can and just pry it up gently. and indeed the white screen was permanent although the phone otherwise was functioning.
so, i'm taking it down to my mates tomorrow or as soon as i get a chance and he's gna have a go at reseating it using his fancy hot air gun rework thingumajig
i would definetly go for the raphael! for the sole reason that it has a VGA screen! (im an ebook nut!) and it looks beautiful!lol
will keep this post updated
i have to agree with mike on this ,there are many problems that can cause the white screen problem. But i am betting that heat is the major culprit,wether it is the IC you mention ,is another discussion, unless of course your friends attempt at reseating the IC cures the problem ,once and for all. Good luck anyway. I am keen to find out if it was successful or not
Hi there
well, he had a look at it under some fancy microscope and confirmed the IC was not sitting 'true' meaning not 100% level, he also used some little jig he had which he sat the board in and it confirmed it wasnt level
so, he heated it, and allowed it to reseat and we tried it again and it appears that did not solve it. we used another flex cable from his own spv and it still didnt work, my cable ran beautifully in his spv too though.
so, im going to find a replacement keypad pcb now and go ahead and buy it and see if i can get it to work
Hi
ive been hunting for the last hour and i cant seem to locate a d-pad anywhere
if i was to use a cingular 8525 d-pad in my vario II it would still work, just button orientation would be different wouldnt it?
do you know of anywhere where i could get one?
I'm having whit screen prob on my wizard and a complet housing case change. I didn't know a keyboard can cause white screen. I was looking to buy a new flex cable. what's the ic and who do I heat?

X1 Ribbon cable - what happens and a fix I came up with!

Hi, I come on here quite a lot for information as it's an amazing resource! This time however, I'm attempting to give something back!
I experienced the "black screen on slide out" on Monday. Phone completely screwed. I've also had a few droppages and had it apart once before so there's no way warranty is gonna help!
I stripped it down and soon discovered what it is that actually fails on the ribbon. The coating had worn through due to rubbing on something during the slide out / in process. it had been playing up for a while, probably due to shorting out on the metal case, but now the tracks (aluminium?) had worn right down.....
In pic 1 i've circled the worn area. The shiny section is where i'd tried taping over it to prevent shorting, before i realised the tracks were gone.
Got an almost new one off ebay for 15 quid and, realising it was going to happen again, came up with a solution that, so far, looks like it will work....
A while back I bought some "anti rattle felt" for my car's dashboard - really thin and strong self adhesive felt to prevent squeaking joins between dash sections. I cut a piece of this and stuck it to the new ribbon. Once this stuff is on it's well stuck, by the way!
See pic 2 for the modded ribbon cable.
On reassembly everything is working just fine so far! Here's hoping that it lasts longer than 6 months this time!
Just need a new casing now as mine is decidedly second hand!
Hope this turns out to be of use to someone!
cool story bro
when i took apart my xperia to replace the housing this seemed like a really weak point in the device. glad to see someone who has had the problem has been able to fix it
Why does the screen go black?
Hi,
When the coating wears off the ribbon cable it exposes the tracks in it. when you slide the keyboard out the exposed tracks short out on the metal casing and the screen loses it's input signal.
thats whats happened on mine at least and i presume quite a few others?
HTH!
Update:
That's interesting: My phone was also losing signal with the keyboard out, and occasionally while closed up as well. It would just randomly drop to "no signal" for a few seconds.
It hasn't done it since replacing the ribbon cable.....could be coincidental of course.
I'm having the same problem
It just started a week ago and I got the phone in January off of ebay. I'm new to opening up the phone so could anyone help me find the correct tools or have a link to a site with pictured instructions?
I noticed that the sliding mechanism started to go loose about 4-5 months ago but didn't expect the screen not respond in landscape mode. I have yet to see the other symptoms you all are referring to. I would like to fix this before it get worse.
In mine case it went totaly black after one week of this problem... You have all the instruction on youtube, there is where i looked. For tools you can be inovative, but the exactly right ones come with housings from ebay, it is only 15EUR, and i bet you have some cracks so it wouldn't hurt replacing. That is what i did, along with ordering new sliding mechanizm, and new ribbon cable.
I am open for ideas to prevent my ribbon cable from being cut at it weakest point again.
I'm assuming my flex ribbon went bad yesterday, since sliding the keypad out causes my screen to shut off.
Already ordered a cable off ebay and will attempt to replace it myself :O
Replaced my flex ribbon cable with one I bought on eBay. The screen doesn't turn on at all now, which leads me to believe the cable I was sent is defective. Put the old one back in and it works okay, less landscape mode. ughhh what a pain.
great tips! my input is I bought a case off of ebay that was ~60$ and everything actually fit fine for me...so I wouldn't discount every seller but you do get what you pay for, the 15$ cases are probablly the ones that will give you problems
I working in a mobilephone repair center if anyone need help drop me a priv... i able to get 2nd hand or even brand new components
Replaced the flex ribbon cable -
I got my flex ribbon cable a few weeks ago and took it to my local repair shop. They replaced it but the LCD screen/optical joystick receives no power. The touchscreen and everything else on the phone works just fine now. I thought it was a defective item so it was exchanged with a new one.
Got the repair shop to replace it again and the outcome still remains the same as the first.
Theres no light coming from the screen nor the side illumination.
I just told the repair shop to just place the original back in for the mean time.
Before the repairs, there would be a flicker of white light and random illuminations. Now there's no lights at all except the power botton.
Could it be defective a batch that the seller was sending out? or the repair shop's mistake and is playing dumb so they do not have to admint fault?
Hopefully there's an easy fix to this problem.
-Also I did inspect the ribbon before and after the repair. looks new as the OEm
Can anybody help me out with this new problem after replacing the cable -
perhaps you should try a hard reset. Ive had problems in the past where the optical joystick and the illuminators did not work, and that worked for me.
On the other hand, the top illuminators are on the same piece of hardware as the flex cable that was replaced, so a faulty flex cable is possible. The bottom illuminators are on the circuit board that the optical joystick attaches to, separate but connected to the flex cable.
Ive recently replaced my flex cable and touchscreen. The experience i had with the faulty touch screen was that it appeared to receive no power, but was in fact displaying a dark backlit illumination that could only be seen in the dark. At the same time however, the screen did not display anything. I'm not sure if this is similar to your experience, but if so then your touchscreen would need to be replaced.
ive done all repairs on the xperia myself, and one thing ive discovered is if something doesnt work right after a repair, simply disassembling it and reassembling it to make sure all the connections are properly done has worked for me in the past.
"Before the repairs, there would be a flicker of white light and random illuminations. Now there's no lights at all except the power button."
Now when you say the power button, do you mean that a red light appears under it?
I dont know if i can come to a conclusion or that i can help (or have helped) you come to a conclusion, but i can only assure you that the xperia acts out in strange and weird ways.
Good Luck!
Tags
Dismantle / Disassemble Sony Ericson Xperia X1
http://www.ifixit.com/Teardown/Sony-Ericsson-XPERIA-X1/788/1
http://www.formymobile.co.uk/xperiadisassembly.php
http://www.youtube.com/watch?v=AWDurQrRt-Y (REAR)
http://www.youtube.com/watch?v=iyGUbxFqvyc&feature=related (FRONT)
http://www.youtube.com/watch?v=elgC8hwHfYQ&feature=related
For info.
Mike
Thanks for the links. I've tried the hardreset and restoring the original rom but the issue is still there. It's really bugging me that everything works but the LCD screen. I'm currently using MyMobiler to use my phone. The touch screen works fine and so does the soft keys. Just no power for the lights. I might just give up and wait for another phone that catches my eye and then tinker with the xperia myself. but if anyone got a solution or want me to test something then I'll give it a try.
My warranty is no longer affective so I'll use my phone as a tester to help others with any problems.
TRIONDAVE, how's your Xperia running now with the cable mod that you did? Its been 6 months since you created the thread. I hope you're still around.
My Xperia X1 works nearly fine, except for the keyboard issues, so I'm thinking of opening it up. If your Ribbon mod helped I might just do it too once I've got it opened. Mine has a MOUNTain of cracks though, and the battery compartment itself is cracked on both side enough to make the compartment CURVED. Hence the Battery cover doesn't sit well.
I'm looking around for broken Xperias which I might be able to use to change the internal cracked casing. Lets see.
DatDereX1 said:
cool story bro
Click to expand...
Click to collapse
My thoughts exactly.
Hello guys, I am in need of real help over here!
Its just that Ive replaced my ribbon cable, the old one got screwd up.
However I got done for 10 minutes ago, tried to start up the phone.. without success :,(
The ribbon cable doesnt have anything to do with the start up, only the screen am I correct? Cause I cannot even start my phone..
Ive connected the charger, but when I remove the battery it shows a red light, meaning no battery, correct?
So what may the problem be exactly? Maybe the battery is all dead, or?
PLEASE HELP!
for the people with ribbon failures how long have you had the phone before it occurred ? im just interested on the cables lifespan.
mine is fine so far but i have noticed the slider is flimsy and rocks left and right.

HERM200 front buttons + Strange behaviour

Hello guys,
All of a sudden yesterday my phone started acting strangely.
1. all front buttons are not working.
2. Green/Red buttons are always with lights on.
3. Phone works too slowly sometimes.
4. Green light that blinks usually does not blink all the time.
5. Camera does not start.
I tried with hard reset too. The phone is not with original ROM. It is now 6.1 but it was working fine for more than 2 years.
Please advice.
Cheers
Yasen
Gorbachov said:
Hello guys,
All of a sudden yesterday my phone started acting strangely.
1. all front buttons are not working.
2. Green/Red buttons are always with lights on.
3. Phone works too slowly sometimes.
4. Green light that blinks usually does not blink all the time.
5. Camera does not start.
I tried with hard reset too. The phone is not with original ROM. It is now 6.1 but it was working fine for more than 2 years.
Please advice.
Cheers
Yasen
Click to expand...
Click to collapse
Did you get mosture / liquid into the d/pad board under the buttons ?
Mike
Hi Mike,
I am pretty sure that this is not the case. I don't remember such event. Also i havent drop my phone recently to the floor or something. It is really strange.
Cheers,
Yasen
Something more...it seems that the screen is not aligned properly. Also when I plug in the phone to the wall charger the orange lamp is not on but the phone charge properly.
So far everything speaks of a hardware problem I'd suggest you take your device to a service shop - unless you are a skilled in soldering etc., this is something you won't be able to fix at home.
i have the same problem too
Indeed it could be the connector between screen and d/pad daughter board as this is also integral to the digitizer that controls the alignment.
It could also be one of the other internal flex cables or the chip on the d/pad daughter board that is known for delicate solder joints.
Mike
I think I will take a part the phone and clean all contact points.
I will write later when I am ready.
Cheers
Yasen
Taking the phone apart did not help
There was quite dirt inside. I have cleaned it carefully. All connectors look okey to me.
On other hand the phone acts differntly every day.
One day the red/green pad is with lights on, other day only the Charging lights is on.
Any sugestions?
Cheers
Yasen
Looks like a broken flex cable or soldering... it might be not something easily detectable with a naked eye. Take a good magnifying glass and carefully examine the flex cables for any cracks, as well as the state of soldering joints, especially in places where the flex cables connect to the mother/daughter boards as well as on the D-Pad board (which receives most mechanical pressure).
If you dare to, turn on the phone while it is taken apart and try to VERY CAREFULLY "swing" the cables with a non-conductive tool to see if it has any effect. Aslo try to apply a bit of pressure (again, VERY CAREFULLY to avoid any damage) to different areas of the boards itself to locate the most probable area where the defective joint might reside.
But, again, unless you're skilled in electronics hardware repairs, the best you can do at home is identifying a potential problem.

Touchscreen: Flexcable damaged due to typical endbutton problem

Hey,
i got the typical problem that my screen wasnt responding after use of endbutton. Sometimes it was working.
I now disassembled the device and saw that the flatcable had a small scratch and i guess the first one or two cables are brocken already and only get contact sometimes by luck.
So does anybody know if there is a way to repair this ?
A new touchscreen isnt to expensive 20-30€ but why throw away a working one if a cable is repairable easily?
Next time i will glue the cable to the display so that there is no flexing when pressing the endbutton. The problem is that there is a little space between that is pushed away each use of the endbutton and someday the problem occours.
Hi,
I had to replace my touch screen to solve the same issue
Is there any thing we can do to prevent the same damage to the new screen ?
Thanks
Well i tried a few times to fix the issue.
But its hard to solder the flex cable without totally burning it.
If i solder it its very likely to break fast again.
Im going to buy a new digitizer too..
To your question:
Yeah i saw that there space between the flex cable and display. The cable is bent a bit towards the buttons. When you push the button the cable is bent back in the free space.
I will glue the flex cable directly to the display and put a layer of protective tape over it. so it wont bent (What causes our error) and wont scratch(if this could happen too).
The problem is the poor quality of the flex cable. Its very hard and therefore breaks easily what causes the wires to break to sooner or later.
If i can ill try to take a few photos but its hard as my digicam cant focus so closely..

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