Toshiba LCD 22BL502B Solid Green Led No Picture

[tom66]

Re: Toshiba LCD 22BL502B Solid Green Led No Picture

It's a little different unfortunately.

Most LED drivers in LED TVs work by using multiple parallel strips driven from a high voltage for example 30V.

This means there may be 4 strips (CH1-4) and the anode is tied to the fixed voltage, cathode goes to a constant current sink circuit which drops a small voltage to keep the current through each strip the same. You can't tie them in parallel because they are slightly mis-matched: one will take all the current leaving none for the others.

I don't know of any commercial drivers that are able to replicate that crucial last part, BUT, you could probably use a resistor in place if you knew the approximate power usage.

For example say the LED strip operates at 27VDC @ 350mA (approx 8 LEDs per CH.) If you run it at 30V, you need a resistor rated at (30-27)/0.35 = 8.5 ohms (nearest: 8.2 ohms, 10 ohms). Such a resistor will dissipate a power of around 1 watt. Choose 2 watt for safety and longevity.

There are a lot of "if", "ands" and "buts" about this, but it would work, if you were prepared to tweak the operation carefully. I would start at around 20~100mA, and increase until acceptable screen brightness is observed.

[tanz0]

Re: Toshiba LCD 22BL502B Solid Green Led No Picture

Thanks.

I understand what you're saying however there is another item here, which is apparently a direct replacement for the screen in question, although I haven't managed to see any part such as this on the assembly. Anyway it has 5 pairs of GND/VCC connections, which I'm assuming are in parallel ? Unless the circuit is performing the current adjustment you speak of.

Thanks.

[tanz0]

Re: Toshiba LCD 22BL502B Solid Green Led No Picture

Link !

http://www.iccfl.com/product_info.php?products_id=16181

[tom66]

Re: Toshiba LCD 22BL502B Solid Green Led No Picture

Those appear to be the inputs, and it takes 24V input.

[tanz0]

Re: Toshiba LCD 22BL502B Solid Green Led No Picture

I think those are the outputs. The other connector is a 6-pin which the screen currently has for a backlight connector. Would you need 5 parallel 24v inputs and separate GNDs ?

I did notice the 24v but I thought might auto-adjust or assumed it was for 24v. I think you mentioned at the start this model operated on 12v/24v.

Thanks.

[tanz0]

Re: Toshiba LCD 22BL502B Solid Green Led No Picture

The glass forming part of the actual LCD display. How important is that ? Minor crack. Is this just to protect internals or does the glass actually play a part in image generation. Something about substrate with electrodes.

Thanks.