Digihome 32DLed906

[ronhayes]

Re: Digihome 32DLed906

Any way back to this dick barton do you think I should remove the jumper set up, as this is not giving me the 25.1v to the LED driver board this voltage was present when the main board was connected to the power supply ?

[ronhayes]

Re: Digihome 32DLed906

I really do appreciate every ones help with this issue without all your input I would not have got this far.
And I appreciate flocko's advice that one dry could cause the driver board to shut down.
But having said that I was very careful when replacing all the LED's and made sure I seen the solder flow on each and every one when installed. now as you all know I mainly have worked on CRT's 20 + years ago so these LCD's and Plasma's are relatively new to me , and these LED's are new to me and to be completely honest this TV and the LG I recently worked on are the first LED's I have replaced.
So you can understand I am not 100% confident with these flat panels and of course I will make some mistakes along the way admittedly some very stupid, some not so stupid.
But if you could bare in mind when I post my results I probably don't always get it right And I may not completely know what I can and cannot do concerning Led backlights but I am slowly learning.
But in no way was I taking a shot in the dark my thought was to eliminate each strip and the way I thought was to test each one not thinking I could cause any damage and of course this way was obviously the wrong way .
What I also can't make sense of, is this LED tester the idea of having a LED tester at your side is so you can test the LED backlights and save the issue of having to strip a LCD panel completely down, but as flocko pointed out they do not work the same as a LED driver board and so therefore they would mislead you into thinking the Led backlights are working fine as they would still light up all the LED's even if some had dry joints or bad connections ?
Sorry if I have waffled on a bit but I really do appreciate all the help you all are giving me thank you all very much.

[ronhayes]

Re: Digihome 32DLed906

Yes it is provided by the power supply but it has not come up with the jumper in place and the main board connecter pulled, But it is their when jumper is off and main board connected ?

[dick_barton]

Re: Digihome 32DLed906

With the mainboard disconnected and the jumpers in place the secondary voltages should come up and also the backlights.

Because I do not have the 25.1v on pin 1 of the driver input connecter.

Isn't that also provided by the power supply so that to should come up with the jumper resistors in place.

[ronhayes]

Re: Digihome 32DLed906

I have just refitted the jumper resisters in place and disconnected the connecter from the main board and plugged TV in to a power outlet, So should I assume when TV is plugged in the secondary voltages should come up meaning Tv would be on and not in a ST/BY mode as the ST/BY on/off pin 6 is jumped to the +5v ST/BY pin 14 via a 1k resister ? and backlights should fire up due to pin 8 B/L on/off jumped to +5v ST/BY pin 14 ?
Because I do not have the 25.1v on pin 1 of the driver input connecter.
And if plugging TV into a power outlet powers TV into ST/BY mode how do I power TV out of ST/BY when remote sensor and on/off switch are connected to the main board ?

[ronhayes]

Re: Digihome 32DLed906

No the main board was connected up ready for normal use as when all Led's were replaced did not expect to have had this issue ?

[dick_barton]

Re: Digihome 32DLed906

Were the last few tests carried out with the main board disconnected and only the jumper resistors in place?

[flocko]

Re: Digihome 32DLed906

One dry joint on any of the replaced LEDs will see the driver shut down.And taking shots in the dark will not end up in a good place, putting 100+v though a strip that should run at about 25v. just as well the driver shuts its self down or you would need more new LEDs

[ronhayes]

Re: Digihome 32DLed906

You know this is going to be a stupid fault in the end maybe a fault I have created I don't know but you can guarantee it will end up being a silly mistake in the end !! I just can't see the wood for the trees.
Will have a break for an hour see if that helps .

[ronhayes]

Re: Digihome 32DLed906

What I have now done is removed the strip connecting board and wired all the Led strips as illustrated in post #89 and then powered up. Led's light up after 5 seconds then go out after a couple of seconds . I then disconnected one strip and bridged across then powered up again the three remaining strips came on after five seconds but then go off after a couple of seconds , I then reconnected that strip and did the same procedure for the next strip I got the same results ! I then tried this on all the remaining strips only to get the same results the three connected came on after 5 seconds then go off after a couple of seconds. I then changed the driver board for the other driver board and the same results.
I just can't fathom this out (I even switched anode and cathode over on driver board )
but the Led's did not light at all. just to see had I connected wrong.
I then connected the fly leads from the driver board to each strip one at a time and I got the same results on each strip would come on after 5 seconds then go off after a couple of seconds this was the results for all strips ?

[vinceroger69]

Re: Digihome 32DLed906

ron you have said you have two led driver boards are these the exact part numbers just wondered if was different as maybe meant for more or less leds.

[flocko]

Re: Digihome 32DLed906

I told you in post 35 that your driver boards were shutting down and the reason why. your new LED tester will light the backlights as it does not work in the same way as the driver board,the fact that the leds flashed on when driven by the driver board shows it to be working, your problem is with the LEDs or the wiring to said strips Hope this is of help

[ronhayes]

Re: Digihome 32DLed906

So am I understanding this correctly , do I reconnect this lead as shown in attached picture ? then set dmm to ohms 20k range de-solder one fly lead on connecter board then check resistance from that pin on connecter board to corresponding pin on driver board ? then do the same with the other pin ?

[budm]

Re: Digihome 32DLed906

Yes, you use that flying leads like that for now so we can do more trouble shooting as to why it goes into shutdown.
I have a feeling if you check the resistance between each corresponding pin on the power supply board to the LED board, you will find no connection or high resistance between the two pints, or you can have one flying lead connected one at a time to find out which original connection is bad.

[ronhayes]

Re: Digihome 32DLed906

Here are some pictures of the fly leads . Just by-passing the connection on driver board and the lead from driver board to strip connection board and connection on board.

[ronhayes]

Re: Digihome 32DLed906

What's baffling me is if I connect Led tester to the driver end of the connection wire all the Led's light up as seen in post#93 but when reconnected to driver board they don't .
It's weird .
O well I will see if I have any better look tomorrow.
What I would like to know is if my mod works could I leave it like this as long as the wires tidy and taped down, or would I have to replace connecter board ?

[budm]

Re: Digihome 32DLed906

OK, that is not the same result with 140V reading which you had before which I do not understand why you are now getting 117V with flying leads connected to the same LED connector. When the Voltage drops down to 24.8V at that point you will not be seeing much Voltage on the Cathode return side.
The 24.8V is the feeding Voltage to the boost converter that put out over 100V to drive the LED string, the Vf of the LED string is about 108V (36 x 3V) + ABOUT 10V Vdrops on the PWM controlled MOSFET and the I sense resistor.
Right now it does not make sense on what you did with the flying leads VS direct connection between the LED strips from the panel to the power supply board via original wires.
You have to be get the same result using original wires without using the flying leads first.

[ronhayes]

Re: Digihome 32DLed906

What I have just tried I soldered two fly leads from the anode and cathode on the connecter board what the Led strips push on to and soldered the other ends to the anode and cathode of driver board .
Then measured voltage on anode of driver board while powering up TV when button pressed the voltage went to 24.8v then after 5 0r 6 seconds it jumped to 117v and the back lights came on for a couple of seconds and as the voltage was slowly decreasing back down to 24.8v they go off they were not coming on before at all .
I also measured the volts on the cathode whilst carrying out the same test and stayed at 3v this time.
I think I need to remove the connecter board and carry out the mod that I posted in post #89 to see if this has any effect .
I will do this tomorrow.

[budm]

Re: Digihome 32DLed906

I do not know what to tell you you have input Voltage to the string but you barely getting anything coming out at the other side of the LED string.

[ronhayes]

Re: Digihome 32DLed906

I know it doesn't add up ?
But if you look at post's #91 and #93 when I connect tester to points on connection board and in post #93 to driver end of connection leads all works well all Led's have a steady light .
And given the voltage inputs on driver board these backlights should come on when set powers up ?