LCD Power Issue

frangolfgt · 08-11-2007, 03:37 PM

Iv'e read the FAQ and If i understand this correctly, you can power your monitor using yellow on a molex as +12V and the black next to it as ground.

I have cut the cig. lighter adapter off the lead that came with my screen and tested which wire is connected to the middle and which is connected to the inner part of the plug that goes into the lcd. I did this with a household 12v dc powersupply that I have, and a 12v bulb. the inner needs to be positive so I have connected the wire that goes to inner to the yellow wire on a molex and the other wire to the black adjacent on the molex and plugged the other side into the lcd.

When I do this however, i cannot turn the screen on without the power going off. I can start the PC with it all connected - it post beeps - and I have the monitor in standby, but as soon as I turn the monitor on, the CPU fan cuts out as though there is a power cut. Then it powers back on with the LCD in standby again.

I have also noticed that if I try to connect a 12v bulb, the same thing happens (the shutdown) and If I keep the bulb connected I can hear clicks and the cpu fan sort of pulses as if its trying to start to spin but then gets interrupted.

The 12V bulb also lights up if i put it beween the +5v and ground connections on the same molex, which I thought couldn't happen (I am a serious electrical newbie so I'm probably wrong), but the screen doesnt work across this (as I thought it shouldn't).

This is not an issue with the molex wires as both (I have 2 on the M2atx) can power the HDD and do the shutdown. The LCD max power consumption says only 8W so I have enough amps on the 12v for it don't I? Or have I totally misunderstood something.

can someone help me as to where I am wrong?

I am using M2atx with no jumpers on and the liliput 619GL-70NP

Thanks

billmee · 08-11-2007, 06:44 PM

Can this molex connector power a hard drive or cd ??
Does the bulb draw similar power?
Are you wiring the lcd with very long and very small diameter wires?

Nice to see another tdi here...

frangolfgt · 08-11-2007, 06:54 PM

yes it can power a hdd - at least when I use either molex in the hdd, the computer can detect it and a cd drive tray opens when powered by it.
bulb draws 10W
wiring is with very short house (240V) wire

Good Fuel consumption, decent power for first car = TDI, what else?

billmee · 08-11-2007, 07:02 PM

You are sure about the polarity?

frangolfgt · 08-11-2007, 07:23 PM

Yes i've tested it like 5 times

billmee · 08-12-2007, 06:32 AM

Quote: Originally Posted by frangolfgt

Yes i've tested it like 5 times

I guessed you had, but had to ask.

I'm wondering if the supply somehow needs a load on the 5 volt supply also available on the connector. I also wonder if the 12v common and 5v common got switched when the connector was made. When connected to the hd the commons were probably cross connected. You could try that.

The HD test proved the connector is valid. Try to simulate that load.
If you have 2 of the 12v bulbs it would be a good start.

frangolfgt · 08-12-2007, 08:00 AM

If i put a bulb across 12v and 5v the same shutdown happens. If I remove the 12v line bulb the 5v line bulb comes on like before. if i remove just the 5v it shutsdown like before.

frangolfgt · 08-20-2007, 01:20 PM

Bump for more help. (OR an alternative way to power the screen?) anyone please help.