Re: Digihome (Vestel) LED Backlighting Problem
The meter is quite old so perhaps it has a fault. Maybe it's time to replace it....
bigalxyz
Member
Last Activity: 08-21-2016, 04:34 PM
Joined: 08-17-2016
Location: London
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Re: Digihome (Vestel) LED Backlighting Problem
Not sure what I'm looking at in that case. 1050 volt drop?! Or could it be showing millivolts? Why would I see the exact same voltage drop number as I see in ohms using the resistor test function. This is all very confusing.
Anyway - I think we've successfully identified the suspect LEDs so I suppose the first job is to replace those and then see what happens....Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I'm not sure what the serial number is on the LED strips - I'll check tomorrow. I've already ordered some replacement LEDs though which I should be able to "stack" onto the existing strips (discussed this earlier in this thread). eBay so they should be with me in a day or two, fingers crossed.
Thanks for your comments tonight, very grateful....Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I thought in diode mode it was measuring resistance, ie 1050 ohms. Is that not the case?
In resistor test mode I get the same numbers ie 1050 ohms in one direction, and open circuit (infinite ohms) in the other direction....Last edited by bigalxyz; 08-21-2016, 03:55 PM.Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
No, very consistent for the good LEDs, all very close to 1050. So I have to assume that's the "correct" number.
As I said, I saw 100 from one of the dead LEDs, 200 from another one, and open circuit (infinite resistance) from another....Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
Yes, that's what I did - I scratched through the surface of the strips before and after each LED so that there is a little bit of copper underneath....Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
No, it's digital. Photo below......Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I worry that I've shagged something elsewhere because the return voltage on one of the leads from the PSU has dropped to zero. But one problem at a time...Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I've quickly tested now. In diode modes the good LEDs (the ones that I've seen light up with my 7.2V battery) show numbers of about 1050. However two of the bad ones give numbers of 100 or 200. And one of the other LEDs shows "1" on the screen which I think means an open circuit, so presumably infinite resistance, no complete circuit and no current flowing?
The bit I don't understand is that I got these numbers by reversing the leads on the multimeter, so that the "ground" lead on the meter (black) was...Last edited by bigalxyz; 08-21-2016, 02:25 PM.Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
Thank you. I understand. I did try using my multimeter in diode mode on Thursday but I can't remember what it told me! (although I do remember that it made the LEDs light up a tiny amount) I'll try it again tomorrow......Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I haven't bridged the connectors to the LED strips, no. My test meter tells me all the voltage coming from the PSU is getting through to the strips as it should - have checked carefully - so I can't see how this would help. Am I missing something?...Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
The two and a half strips that work - voltage drop across each bulb is 2.4 - 2.5V, nice steady bright light.
The two and a half strips that don't work - voltage drop across each bulb is ALSO 2.4 - 2.5V, but they just barely light up. Not only that, but they stay in their just barely lit up state when I put the TV in standby mode!Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
Correct - the other two faulty bulbs are in the middle row (with the black arrows next to them). Not apparent from the photo though - tested with a 7.2V batteryLeave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
TV failed last week. Switch on, fine, but screen goes blank after a couple of minutes. Restarting the TV fixes the problem but it keeps recurring.
Sometimes the left half of the screen only goes dark and the right half stays bright, before the whole thing fails.
Dismantled TV, done lots of checking of LED bulbs, voltages at various different points, etc. but I'm struggling to make sense of it. Don't think LEDs are all faulty on one side of the screen (3 individual bulbs have failed on the...Last edited by bigalxyz; 08-21-2016, 11:41 AM.Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I've been able to test each of the LEDs by applying 7.2V DC across two bulbs at a time (voltage drop 3.6V across each bulb). 3 individual LEDs aren't working but the rest seem to be ok....Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
Not yet because I spent some time this morning checking the voltages at various points, and the voltages from the PSU are getting through to the LED strips perfectly.
And yet half the LEDs don't light up. Sometimes they light up nice & bright when you first switch the TV on and then go out after a few seconds, but usually they stay dark.
The other half of the LEDs work ok (save for a couple of dead individual bulbs which I've ordered the replacements for).
I can't make...Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
Understood - hence the voltages from the PSU vary a little bit from time to time. I still don't know what the fault is with my set though. Very confused.Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
I'm still unsure about my situation.
Even for those LED strips that are malfunctioning on my TV (the 1st, the 2nd and half the 3rd), the voltage gets through to them absolutely fine - it marries up perfectly with the voltages that appear at other points on the circuit boards at the top. No sign at all of any broken connections.
Something has changed though. The voltages I was seeing the other day for the 3 leads from the PSU were:
28V red, 28V brown, 72V black
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...Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
Thank you once again. Just ordered some. Think I'm done for today. Will wait for postie to bring my stuff and then get cracking....Leave a comment:
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Re: Digihome (Vestel) LED Backlighting Problem
[url]http://www.ebay.co.uk/itm/252492958756[/url]Re: Digihome (Vestel) LED Backlighti...92958756[/url]...Leave a comment:
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