Digihome 32DLed906

[budm]

Re: Digihome 32DLed906

So it uses LED backlights with same high Voltage connector that is typically used for CCFL High Voltage backlights. Pin 11 of the LED driver board connector shows LOW (<0.7V)?
If LED string has open circuit then it should go high.
Meter in DCV then put the black probe of the meter to chassis, red probe on pin 11 and then turn on the TV and watch to see if it jumps >1Vdc.
Hope fully that High Voltage CCFL tester did not damage the LEDs.
Also test the DCV on the LED connector with ref. to chassis GND.
Test procedures:
TV off, red probe one on of the two LED connector then turn the TV on, record the reading and wait 5 seconds to see what it settle down too then turn the TV off.
Red probe one the pin of the two LED connector then turn the TV on, record the reading and wait 5 seconds to see what it settle down too then turn the TV off.
Too bad the spec sheet does not show the Vf of the LED string.

[ronhayes]

Re: Digihome 32DLed906

Pin 14 of pl804 is reading 0.01v pin 12 is reading 0.03v while st/by light is flashing on/off

[flocko]

Re: Digihome 32DLed906

two strips of 11 LEDs are fitted to this panel, so you would be looking for around 76v DC to drive them.after having a good blast of HT I dont think they will be at there best,but stranger thing have happened

[ronhayes]

Re: Digihome 32DLed906

Pin 11> goes to 0.09v in 20v range
one pin off led connector 1.45v then settles at 3.05v
second pin of led connector 13.33v settles at 13.45v
Same results with led plug in or removed

[ronhayes]

Re: Digihome 32DLed906

Going to work in 20 min I am on nights this week.
Will carry on tomorrow afternoon after sleep.

[vinceroger69]

Re: Digihome 32DLed906

have you got one of theses led testers? these make testing the leds easier and saves stripping the lcd panel down
http://www.ebay.co.uk/itm/SID-GJ2C-0...oAAOSw8a1ZuQy1

[dick_barton]

Re: Digihome 32DLed906

If you repeat the test as in post #6 and then check the voltages on the led driver board are there ie 24V, Status, VOn/OFF

Next with your meter on one of the pins going to the leds, power up again (mainboard still disconnected) and check if the voltage peaks then drops.

[ronhayes]

Re: Digihome 32DLed906

Hi All
Update on this Digihome !
I sent for a replacement motherboard for this set as it was not to expensive and also the driver board was only a couple pounds so sent for that two.
When the motherboard arrived I installed it and the TV now powers up I have picture and sound but no backlights !!
Now given the fact that I had not tested led backlights before and had used the backlight tester that came with my LCD tester kit and which (flocko ) had suggested could have caused damage to the LED backlights I decided to send for a LED tester as suggested by (vinceroger69)
Now while waiting for the delivery of the LED tester which is about three weeks I decided to rig up a single LED tester using two AA batteries and a couple tester leads giving me a 3v tester and dug out my old vintage variable power supply .
I then applied 70v to the backlights at a slow pace to see if they would fire up they did not, So I then disassembled the LCD screen to expose the LED backlights there are three strips of 9 LED's applying 27v directly to each strip only one fired up I then started checking each LED on the two faulty strips using the 3v tester I had made I found two faulty LED's on each strip I replaced them and tested each strip they seem fine. I then tested all three together with variable p/s with 80v all ok.
Then reassembled the screen and powered up the TV.
Now what I get is a good picture for about 2 seconds then the backlights go out TV stays on , I then disconnected the LED plug and applied 80v with my variable p/s and the backlights stay on!! I have tried both of the driver boards the original and the replacement and they both give the same result backlights for 2 seconds then backlights going out ?
Any suggestions much appreciated.

[dick_barton]

Re: Digihome 32DLed906

Had you also replaced the driver board?

[ronhayes]

Re: Digihome 32DLed906

yes

[dick_barton]

Re: Digihome 32DLed906

So what voltages do you have on the led driver board input connector Pin 1,11, 12 & 14

[ronhayes]

Re: Digihome 32DLed906

Hi all
Back on this set now.
I switched this set back on tonight and would you believe the it backlights stayed on !!
But what I have noticed is there are a few bright spots on the screen . So thinking maybe the replacement led's I had put in maybe the diffusers had come off so I striped the screen down again and all looks ok.
So now I am thinking are the ones I put in shining brighter then the originals and as (flocko stated in post #23 giving them a blast of HT are they now stressed and would I need to replace all)
It looks like I may have to ! Oh well never mind I will post the out come when I have done this.

[dick_barton]

Re: Digihome 32DLed906

I think one of the problems is to ensure that the lens's are fitted correctly over the leds. It is also possible that the replacement leds are higher brightness than the originals. That's why if not too expensive I tend to buy a strip for that set and use the leds from them.

[ronhayes]

Re: Digihome 32DLed906

Hi All
Back on this set this weekend.
Now I dismantled the screen and checked the led's again and found two more had gone so I replaced them and checked the diffusers on the ones I had already changed and removed them and made sure they were seated over led's as close as possible over the led's.
I reassembled the set and switched on only to have no backlights again, I tried both driver boards no backlights.
I supplied 80v to led's with variable power supply and screen came on picture looked better.
Here are the voltages on the input connecter of driver board.

200v range
pin 1 in ST/BY 00.0v powered on 25.1v

20v range
pin 11 in ST/BY 0.00v powered on 0.01v
pin 12 in ST/BY 0.00v powered on 3.44v
pin 14 in ST/BY 0.00v powered on 3.04v

On output to Led's connection in 200v range + pin on ST/BY 00.0v when powering on goes to 130.0v then slowly decreases to 25.0v stays steady at 25.0v.
pin - on ST/BY 01.0v stays at this when powered up.

[flocko]

Re: Digihome 32DLed906

Your LED driver is detecting an overcurrent on the LED strips and shutting down.The replacement LEDs that you have fitted are pulling to much current, that is why they look to be brighter. LED string drivers work on limiting the current to the strips as you will see the LED strip supply voltage ramps up then drops back as the IC tries adjust the running current that is preset on the board. Hope this is of help to you Flocko

[ronhayes]

Re: Digihome 32DLed906

Thank you Flocko
So do I need to replace these LED strips completely to cure this fault ? Have searched for a set of four for this model but no joy.

[vinceroger69]

Re: Digihome 32DLed906

whats the specs of your replacement leds your using

[ronhayes]

Re: Digihome 32DLed906

Product Model : 3528
Product specifications : 2.8*3.5* 0.8mm
Product maximum power 1W
The product voltage range 3.0v - 3.7v
The maximum current of the product 280ma
Product color temperature 15000-20000K (cold white light)
Product luminous efficiency 100-110LM/W

[vinceroger69]

Re: Digihome 32DLed906

maybe flocko can look at the led specs and advise us ron whats the part numbers on your led strips i will have a look at my spare strips and see if i have any which i salvage through smashed screen sets

[ronhayes]

Re: Digihome 32DLed906

Thanks vinceroger69
The set is all back together now so I will have to strip it down again later and then I can check the part number on the LED strips.