Re: LED Driver board Question
Fun fact: When I put it back in the guy asked could we increase the backlight brightness. I thought it looked fine but with the replacement I've made it has reduced the brightness, so the resistance value we were talking about does seem to have something to do with the level of current passing through the LEDs.
JonathanAnon
Badcaps Veteran
Last Activity: 09-11-2021, 02:48 PM
Joined: 07-16-2012
Location: Kildare
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Re: LED Driver board Question
Okay, I've put it all back together. A million screws of course.
Just to re-iterate, I have not made any changes since the start of the thread. I have replaced the open 2R and R330 resistors with one 2R2 resistor and it has been on for four days solid without any issues.
I'm gonna run with this. thanks.Leave a comment:
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Re: LED Driver board Question
If I swop the 2R2 for a 1 ohm resistor and measure the current will that settle the argument
Leave a comment:
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Re: LED Driver board Question
I put the clamp on the two positive wires coming out of the driver board feeding the LED strips. Does seem low to me but that is what it reads.
Sorry Bud, I meant to say this - there is no means for the user to change the backlight through brightness setting or the like. There is no remote control. So the backlight current will be fixed....Leave a comment:
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Re: LED Driver board Question
Okay I used my induction ammeter to measure the current as well. There's no obvious location to break the circuit to introduce a series ammeter, so clamp is the best I'm gonna have for the moment.
200mV voltage drop across 2R2 resistor. 200mA current on the induction clamp.
P=VxI = 0.2V x 0.2A = 0.04 Watts.
So, the 2R2 resistor will have to dissipate 40mW.Leave a comment:
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Re: LED Driver board Question
Hey guys,
It's been on for two days solid with the 2R2 resistor. Backlight is more than adequate.
Voltage drop on the 2R2 resistor is 200mVLeave a comment:
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Re: LED Driver board Question
I have an LED tester in the post Bud, can't get there here in any shop in Ireland somehow. But it should be here shortly. There's a big digitiser fitted in to the main steel frame - So it's interactive as well. It's actually really cool when it's back together. Would be a hell of a gaming machine if I downloaded the MAME emulator.
4 x 26 LEDs on each strip, and two strips, so total of 8 x 26 LEDs...Last edited by JonathanAnon; 08-12-2020, 01:36 PM.Leave a comment:
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Re: LED Driver board Question
Hah, well you can do that for sure, but I'm downloading Garageband first....Leave a comment:
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Re: LED Driver board Question
Just one more image to give you an idea of what I'm looking at right now. I took apart the 50 inch panel completely to get at the backlights, so I'm very relieved that the screen seems to be okay.
This is the level of light I get with the 2R2 resistor in place....Leave a comment:
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Re: LED Driver board Question
Closer shot of the chip.
...Leave a comment:
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Re: LED Driver board Question
Exactly, and I was looking for the terms that described them thanks.
You will notice that if you search for v500hj1-pe8 LEDs, you will find something like the link below.
[url]https://spares2repair.co.uk/sound-vision/led-tv-backlights/innolux-led-backlights/v500hj1-pe8[/url]
And these are not the LEDs in my version. My version has edge LEDs similar to this:Re: LED Driver board Question<br /> ...d them thanks....Leave a comment:
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Re: LED Driver board Question
innolux v500hj1-pe8 is the panel. Just be aware that the LEDs that they sell for this one are NOT the same as what is in this panel. The LEDs in my version of the screen are all at the bottom of the screen, there are two LED strips and each has four parallel sets of 26 LEDs. The back of the panel says 720ma / 78-89V
It is a store display unit where people can walk up to it and look for websites and they can run demonstration videos on. If I was to describe it, it looks like a 6 foot mobile phone. My seven year old nephew asked me what it...Leave a comment:
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Re: LED Driver board Question
From the pics I currently that's the best one Bud. I'm not sure if you can work it out from that. I'll take another pic later....Leave a comment:
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Re: LED Driver board Question
Yeah I am concerned by this also, but I have tested the backlight LEDs with a tester and they work fine, and even with just that 2R2 resistor in place they all turn on fine. Because I dont know what caused them to open, I would like to reduce the current a little if possible. And I will leave on test a long time giving back.
You mean my option of using the 5 2R2s in parallel giving 0.44ohms?...Leave a comment:
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Re: LED Driver board Question
I see it. It must be pretty forgiving, as I have increased the resistance at that junction from 0.29 ohm to 2.2 ohm and still the backlight comes on and stays on. I think I'll just replace those resistors with exactly what was there previously.
thanks.Leave a comment:
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Re: LED Driver board Question
My apologies, I had the output cable turned upside down. I just noticed A and C on the output connector, which I presume is Anode and Cathode of the LEDs - so those resistors connect the cathode side of the LEDs to ground.
There is nothing on the back side of the board. So I think the purpose IS current limiting, not current sensing. I dont want to take up any more of your time, guys, so I think I'll just get the same resistors as what was in it. I will improvise on the next one!
...Last edited by JonathanAnon; 08-11-2020, 02:12 PM.Leave a comment:
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Re: LED Driver board Question
Interesting Dick, I didn't know that they need to be that finely "tuned".
So here's my plan. The resistance that would have been there originally would have been 0.28 ohms (2ohm and 0.33 in parallel). Now, I have a load of 2R2 SMD resistors, so I'm gonna put five of them in the parallel on the available pads which gives effective resistance of 0.44 ohms. This will reduce the current, which is what I want, and will also mean I don't have to order any small bits in the post. I will checked afterwards to make sure that there is...Leave a comment:
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Re: LED Driver board Question
Yes, I understand. But the bit I'm curious about is why there are two different resistor values. The circuit will see the effective resistance of the two resistors in parallel.
I have two options here:
1. Buy exact replacements for the two resistors in the circuit.
2. Use slightly higher resistance to reduce the current through the circuit.Leave a comment:
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LED Driver board Question
Hi there,
I have been given a store display panel to fix, The output of the B20N15D MOSFETs are fed to the output connector through parallel two resistors, which 2R00 (2ohm) and one R330 (0.33ohm), giving effective resistance of 0.28ohm. Both of these are open and need to be replaced. I replaced both temporarily with a 2R2 resistor and the TV works fine.
I could understand why you would have two resistors of the same value (so as to increase the power you can carry), but I just don't understand why you would have two resistors in parallel with such differing values.... -
Re: Dead Vestel 17IPS71 power board
[QUOTE=dick_barton;968967]When the voltage on the capacitor reaches a set point (data sheet) then the internal circuit switches off and allows feedback from the transformer (N3 winding) to maintain that voltage.[quote]
Is this common now? I haven't seen that before on any of the other TVs I've worked on. I guess I will know to look out for it now.
Yeah I checked it it's good. One bad diode on the secondary side but I got that sorted.
Yeah I always use the main filter cap ground as the ground...Leave a comment:
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