Black Screen on Toshiba Satellite P75-A7200 Laptop

[fredrok46]

My laptop won't start. When I press the power button it goes directly to a black screen.
The LEDs light up, the fan spins for a moment but that's it. I have tried all the usual suspects: An external monitor, Factory reset (Zero + Power), R&R battery, Power button hold reset. No help.

I hear a faint ticking noise (definitely not the Hard Drive) coming from where the power cable plugs in.
It starts when I press the power button and stops when I press it again. I have it disassembled as shown in the screenshot. The first arrow shows the power socket. The second one shows where the cables run up to the monitor. The ticking noise could be coming from either.
Anyone have any idea what this might be?

 

[Megahertz07]

It may be the power supply of the MB. Did you try to take out the battery?

 

[fredrok46]

Yes, I replaced the motherboard BIOS battery. I was hoping it would force the BIOS to it's defaults. I think the power supply is fine because the LEDs come on just as they are supposed to. One comes on when I attach the power cable and the other comes on as soon as I push the power button.
If I could figure out a way to set the graphics to default I think it would start. This computer belongs to a near blind person and so the graphics settings are extreme and Windows Magnifier is always on. Any ideas on how to do that in it's present state?
The only other clue I have is that ticking noise.

 

[Megahertz07]

If the main battery is defective it can explain the ticking noise.
- Try to boot without the main battery and without the HDD.

Don't think that he graphics settings has anything to do. On boot it runs as VGA.

 

[fredrok46]

I had already been trying to start it without the battery so after your last reply I tried it with the battery in. I noticed right away that something was different. With the battery in the LED that lights when power is connected turned red. I pushed the power button and I got an on-screen message that the battery was low and I should press an F button. I was out of time to work on it and foolishly just turned it off. Now I can't get that message back no matter what I try. Can you advise me further? We were so close. At least we know the screen works.
Do you think a new battery would fix it?

 

[Megahertz07]

Don't think that a new battery will help, as the computer should work without one.
You booted with the little battery power.
I think that you have a power supply failure (internal or external).
Try another external power supply (normally 19 Vdc).

 

[Sky Ranch]

That ticking sounds like the relay. Could be caused by a faulty external power supply (unstable voltage output) or the relay itself. If it is the PS on the MB then it's probably more trouble than it's worth to try and fix it.

 

[fredrok46]

I know it should start without the battery installed but It did give that onscreen message one time about the battery being low and to press F2. Still kicking myself for not doing that. I can't get that message to repeat and the LED doesn't turn red anymore when I install the battery. I think maybe the battery is so dead now the laptop doesn't know it's there. If it might help I could buy an external charger and try it again. What do you think?
I went through it and tried to find out what was causing that ticking sound. I disconnected the cables one at a time until I found one that stopped it. That was the graphics card. I took it out and the ticking stopped, I put it back in and still no ticking but that didn't help anything.
I had the MB out and can't find anything visually wrong with it. Should I expect to?

 

[Megahertz07]

When you booted with the battery on, it still had some charge, now it's gone.
The battery isn't charging and the laptop doesn't start. It means that one of the power supply is defective.
If it's the internal, on the MoBo, as Sky Ranch mentioned, then it's probably more trouble than it's worth to try and fix it.
If it's the external, that is quite simple to replace. You can even try from another laptop. Check output voltage fist.

 

[fredrok46]

I have several external laptop power supplies but none of them will fit in the power jack of this computer. Is there a way to work around that?

 

[Megahertz07]

Fist of all, you must be sure that they have same output voltage and same polarity. Normally the center is positive and the out contact is negative. This should be in the power supply label.

Can you take a photo of the two connectors?