Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Hello Elviscocho,
Yes, I resolved the issue. Problem was in the led strips.
zarko
Member
Last Activity: 07-03-2023, 04:21 AM
Joined: 03-16-2019
Location: Belgrade / Serbia
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Thank you Diah & diif.
I will stay with 4020.
I guess it is Aliexpress then.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
I have analysed those 4020 LEDs that are working fine.
This is what I measured:
Voltage applied:___| 5.5V | 5.75V | 6.00V | 6.2V
Measured current:_| 20mA | 40mA | 60mA | 80mA
Measured current is nor exactly the same for all LEDs, this is average value.
I am thinking of switching to 2835 LEDs.
I have found this LED in a local store but I am not sure if it would be suitable for LCD TV usage.
[url]https://store.comet.rs/Catalogue/Product/48222/[/url]Re: Sony...Last edited by zarko; 03-25-2019, 06:51 PM.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Both caps are 10uF, 450V.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Yes it is 56 LEDs in series per strip (one group).
I tried LEDs with 3V at fIrst but I could not get them to shine.
After that I tested LEDs with 6V, all LEDs are shining except 5 LEDs which are bad.
I expected one LED to be bad. How come 5 LEDs were open connection?
On PSU there are two connectors for LED back-light. Two pins per connector.
Photos attached....Last edited by zarko; 03-22-2019, 07:01 PM.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Here is a photo of bottom side of LED. No pads.
I will go with 4020, 6V, 150mA.
I have few questions regarding SMD LED soldering, I have no experience with this type of components.
What is the best way to solder SMD LED without pads?
Can I try with soldering iron or I should skip it and go with hot air station?
What is max allowed temperature if I go wit hot air?
Thank you....Last edited by zarko; 03-22-2019, 02:55 PM.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
7mm is larger than LEDs on this strip - photo attached.
I think I could fit 7030 LED if i scoop the white paint from copper.
I found that 4020 LEDs can be found on Aliexpress too, but maybe I should go with 7030 since the quality is probably better.
Maybe I should go with replacing all LEDs? I assume 7030 would last longer than 4020.
What temperature is OK for hot air station when working with SMD LEDs?...Last edited by zarko; 03-22-2019, 02:51 PM.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Yes, definitely 4mm x 2mm.
Photos attached....Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
I have measured, LED dimensions are 4mm x 2mm.
I removed one LED, layout can be seen on attached photo.
What temperature should be used for hot air soldering of SMD LEDs?...Last edited by zarko; 03-22-2019, 12:53 PM.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Additional photo of LEDs.
This one is more precise....Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
I have disassembled the panel.
There are two strips mounted on one aluminum cooler, each strip contains 56 LEDs.
I have tested LEDs using voltage slightly under 6V (there are 5 LEDs broken on one strip, all LEDs are OK on other strip).
I presume that LED voltage is 6V but I found that there exist also 6.2V LEDs.
It seems that supply voltage should be over 336V per strip. I have measured 200V on my PSU.
LED dimensions: 4mm x 2mm
Strips are made by Foxconn (F420LB002-002) - can...Last edited by zarko; 03-22-2019, 06:27 AM.Leave a comment:
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Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on
Thank you Diah.
I will take screen apart and check all LEDs.
But I think that there might be something else besides the back-light LED short.
I have tried turning the TV on without back-light connected to PSU. TV shuts down just the same.
Should the TV shut down if back-light is not connected to PSU?
Does anybody know specs for LEDs used in this TV?
Is it 3V or 6V, what is the LED current?Last edited by zarko; 03-20-2019, 07:35 AM.Leave a comment:
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Sony Bravia KDL-42EX440 - problem - turns off after switching on
My parents gave me a Sony KDL-42ex440 TV to repair it for them.
When I plug the TV in mains, the power LED (green) turns on immediately. After few seconds the back-light flashes for a moment and immediately back-light goes off.
After about 5 seconds TV shuts down (no LED is on). The slight pop sound can be heard from speakers while the TV switches off.
If I want to turn the TV on I must unplug it from mains and plug it again.
I have tried and I can confirm that panel is showing picture after the back-light flash (while the back-light is not on) - I pointed... -
Re: New Members - please post your introductions here
Hello, Zarko here from Srebia. I have a degree electrical engineering (mechatronics). My interest in electronics started while I was in secondary school and I am still very much into electronics. I like doing projects on PIC microcontrollers, audio amplifiers (mainly based on ICs but I also made one with electronic vacuum tube). I also like repairing electronic stuff for my friends and family. My first computer was Sinclair ZX Spectrum 48k+, after that i switched to Atari 520STFM (I upgraded it to 4Mb using ICs), after that I...Leave a comment:
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