My Screen Won't Turn On

XFactor · Post by **XFactor** » Wed Apr 12, 2006 7:05 am

I had everything wired up to show my friend in anticipation that my entire system would work. I flicked the power switch and...

the screen was black.

I wired my entire system per the diagram made by Neildo 64. The Nintendo 64 works (i have played it on battery power on my tv) so that's not a concern. The only problem is the screen.

I wired the screen off of the two diagrams i had: the sticky in this thread and Nieldo's. However, there is a confliction in both of them as to what pin on the 1-12 socket is the ground (one lists it as being pin 7, while the other lists it as being pin 8 ). I tried both; nothing worked. I also tested the voltage coming into the unit via a multimeter and got a voltage of 1.08v. That's way to low to power the screen, as it needs a minimum of 5v.

I also am wondering that possibly that the reason for such a low voltage is because of the resisitor i am using to power the LEDs. I have a 510k-ohm resistor, because my LEDs run at 18,000mcd. I am wondering if this value is to high; however, i also tested the resistance coming across the resistor and found that it was far under its proper level (.054k-ohms).

I am theorizing that the problem is originating from the N64 Mobo by it not allowing enough power to go to the screen. I attached the ground to the ground pin located in the video port of the N64 and I attached the positive lead directly on the line where the battery outputs 7.4v.

If anyone could help me in my situation that'd be fantastical.

EDIT: I also wanted to ask: is it right that i have to remove the transformer from the screen to conserve power? I did that as well per the instruction of the guide at extremetech.com.

Post by **marshallh** » Wed Apr 12, 2006 9:38 am

Holy cow man, you're using a 510Kohm resistor!!?? You're supposed to use only a 10 ohm resistor. Big difference there.

timmeh87 · Post by **timmeh87** » Wed Apr 12, 2006 9:46 am

yeah i was gunna say, your leds arent going to be turning on with such a big resistor in there.

also, the screen needs more like 7.2v to work.

if youre confused about where to stick your ground, just scrape some paint off near the edge of the board, where the unnescecarily huge grounding plane is. thats what i did, instead of mesing around with pins...

also... are you sure you know how to use your multimeter? not to insult you or anything. but if you bought a 510kohm resistor, then theres really no reason it should be reading 54 ohms. (however, if it really is a 54 ohm resistor, the leds should be turning on)

also, if you connected all the LEDS in series, they would need like 9v to operate properly. possibly more, depending on how many there are. you probably need them in a series-parallel combination.

vskid · Post by **vskid** » Wed Apr 12, 2006 9:50 am

So what wattage should the resistor be? The guide uses a 1/2 watt, but all I have are 1/4 watt(I bought the 500 pack from radioshack).

timmeh87 · Post by **timmeh87** » Wed Apr 12, 2006 9:52 am

well, figure out the power dissipated by the resistor.

P = VI
P =I^2R
P = V^2/R

any of those equations will give you the same answer.

(i think a 1/4 watt should be fine. worse case it gets fried, then you have to spend 15 more cents on a new, bigger one)

vskid · Post by **vskid** » Wed Apr 12, 2006 9:56 am

Couldn't I have two in parallel or one for each LED?

EDIT: Just so that I wouldn't have to worry about replacing it.

timmeh87 · Post by **timmeh87** » Wed Apr 12, 2006 11:02 am

two in paralell will cut the effective resistance in half. Im pretty sure each resistor will still recieve the same amount of power.

but i also dont think a 1/4 watt resistor is a problem. everyone uses them.

Post by **CronoTriggerfan** » Wed Apr 12, 2006 4:29 pm

marshallh wrote:Holy cow man, you're using a 510Kohm resistor!!?? You're supposed to use only a 10 ohm resistor. Big difference there.

Ya, that's definitely your problem. There's like NO POWER getting to your LED's! Oh, and about using a 10 ohm... not a good idea. I know it recommends it in Ben's book, but when I used a 10 ohm on my PSOne screen, it stopped working after a while and then the resistor burned to a crisp. Turns out it's WAAAAY better to wire 2 10 ohm resistors in a series or just use one 22 ohm resistor.

G-force · Post by **G-force** » Wed Apr 12, 2006 4:36 pm

Yeah I noticed that a 10 ohm is too small when I typed it into an resistor calculator and I got around 20 something. Why would ben tell people to overdrive their LED's?

timmeh87 · Post by **timmeh87** » Wed Apr 12, 2006 4:45 pm

i was once told to use 110ohm resistors with generic red LEDs...

anyways, im just going to hook mine up to a 1k trim pot. ill only need to use the bottom 10% of it, but thats still like a full turn.

XFactor · Post by **XFactor** » Wed Apr 12, 2006 5:07 pm

So are you all saying the 510k-ohm resistor is what i causing my screen to not work?

Also, am i correct in that i am wiring the ground to the video port pins of the N64 as Nieldo's guide diagram suggests?

Also, where the freak is the ground? Is it the 7th or 8th pin on the 12 pin socket?

Anyways, let me take some photos and i'll be back up here shortly. Then you all can see my disaster.

BTW, Timmeh, yes; i do know how to use the multimeter.

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Wed Apr 12, 2006 5:25 pm

yes, change the resistor to a 22 ohm or a 10 ohm

XFactor · Post by **XFactor** » Wed Apr 12, 2006 6:29 pm

I just changed it to 20 ohms of resistance; no result.

I am going to take pictures to show what i've done. I hope someone can help me here because i am stumped as to why this won't work.

Front:
<a href="http://img140.imageshack.us/my.php?imag ... 04a8kb.jpg" target="_blank"><img src="http://img140.imageshack.us/img140/8353 ... 8kb.th.jpg" border="0" alt="" /></a>

Back:
<a href="http://img140.imageshack.us/my.php?imag ... 05a0sy.jpg" target="_blank"><img src="http://img140.imageshack.us/img140/839/ ... 0sy.th.jpg" border="0" alt="" /></a>

timmeh87 · Post by **timmeh87** » Wed Apr 12, 2006 6:52 pm

can you confirm that the LEDs are coming on? if they arent, youre not going to see anything on the screen

the leads from the LEDs arent shorting against that metal sheilding are they?

Corscaria · Post by **Corscaria** » Wed Apr 12, 2006 6:59 pm

any chance you are trying to power the any of the LEDs backwards? Unlike lightbulbs LEDs are polarity sensitive.