Sony PSone LCD officially works with 12v... Other ?'s!

[riva16]

I don't know / care if anyoen already knows this. I couldn't find it when I searched becuase the search function on these phpbb forums SUCKS! Anywho... When you apply a 12v source directly to the official SONY PSone LCD, it DOES work... Its obvious it works becuase of the 5v regulator, 7508A... These regulators usually can have an inout up to 36v, and still regulate at 5v... I got tired of trying to figur eout how many ohms it would take to bring 12v down to 7.2-7.8, and just wired a 12v source directly to 7508A. If anyone could help, what resistor WOULD I need to bring 12v down to 7.2 - 7.8? I know 470 ohms brings 12v down to 3.3, but when I did all the math, nd broke it down, I got 295 ohms or so... When I applied 295 ohms tot he 12v source, I STILL got 12v...
Kyle

[marshallh]

When I applied 295 ohms tot he 12v source, I STILL got 12v...

Did you test this with a multimeter, when no load is present? I did the same thing, resistors only work when the right amount of current goes through them.

Basically, you can't measure voltage drop from a resistor with a multimeter. Just doesn't work.

[riva16]

Scratch this idea... Running 12v through the 5v regulator does something to the screen. I noticed monster changes when going from 12v directly to the 7508, and just plugging in the power adapter. The circuit must split from the 5v regulator's input to somewhere else. If it was JUST the regulator, you would be able to run up to 36v to the LCD without problems. Just heat issues from the 7508. Things I noticed were, the screen has lines, like refresh lines, running htrough it. Brightness jumps around, and the on screen birghtness / volume indidcators are dim, and look like the LCD is damaged. It's not, in my case... The only option i got is a 7.5v regulator that patches off the 12v supply of my computer. And if resistors don't drop voltage, why does 470 ohms bring 12v down to 3.3? I know this works, i used it before!
Kyle

[nos_slived]

The screen has additional components between the power in, and the 7805, which won't work over 9V. The phpBB forum search doesn't suck, you just need to set up the parameters correctly. Resistors will work with very low currents, but based on ohm's law, if you don't have any current, your votage won't drop. You said that a 470Ω resistor will drop 12V to 3.3V, but that's dependent on the current draw.

[timmeh87]

when will you kids learn that you cant regulate voltage with resitors? if you could, there would be no market for voltage regulators!