HP HSTNN-105C is a Laptop Battery,http://www.usbphoneworld.com/hp-6120-hstnn-105c.html
Look on the bottom of the laptop, and in the white Service Tag.
Give me the Product Number. (P/N)
S/N = Serial Number. Do NOT give out on a public forum. ONLY to authorized HP dealers, and repair shops ]
According to the website in the link above, this battery may fit;
HP Compaq NC6000 series, NC6120 series, NC6220 series, NC6400 series, NX6100 series, 6710B series, and 6910P series of Notebook PC's.
IF the above holds true there is NO panel to simply just remove, and you have access to the CMOS Battery. (Also referred to as RTC Battery. Real Time Clock Battery)
You MAY have to completely disassemble the laptop down to the motherboard in your hand. The CMOS battery is located on the Bottom of the motherboard.
HP Compaq NX6110 series is different. With these type of models the Keyboard is removed, to gain access to the RTC battery,http://www.hardware.com.br/tutoriais/manutencao-notebooks-nx6110/parte.html
The above is in Spanish, and you are on Page 2. (Parte 2)
Posted for the photos.
Scroll the page down, and look at the second, third, fourth, and fifth photos.
The CMOS (RTC) Battery is the round silvery looking object, with the red wire attached.
There is a PROPER procedure for removing the RTC Battery. It isn't just remove the Keyboard, and replace the Battery.
1) ALL power is removed first. Remove the AC adapter (Charger) and Battery.
2) FOLLOW Anti-Static Precautions. Static shock your laptop, and you will have an expensive doorstop, or paperweight.
3) The Keyboard does NOT have to be removed all the way.
Once you post what Product Number you have, I can give you detailed information.
Before we begin;
I would like you to attach an external VGA monitor, and see if the display is OK on it.
1) Laptop OFF, monitor OFF. Attach a VGA monitor to the VGA port on the laptop.
Do not know what HP Compaq laptop you have, can't give you detailed info of where your VGA connector (Port) is on your laptop.
This is an example of a VGA connector, and a VGA cable,http://en.wikipedia.org/wiki/VGA_connector
External VGA monitor:
You can use a CRT monitor, (Looks like a small TV), or a flat LCD screen monitor that has a VGA cable.
2) Monitor attached turn it on. If a CRT type allow it to warm up.
Turn the laptop on.
By default the display should show on the external VGA monitor.
There are however at least 3 display options;
A) Laptop internal monitor ONLY
B) Laptop internal monitor AND external VGA monitor
C) External VGA monitor ONLY
Press, and hold down on the Fn key. At the same time tap once on the Display Toggle-Over key.
Which one is it? It is one of the F keys at the top of the Keyboard.
F2, F3, F4, F5, and so on. It will have a monitor symbol on it, and a second one connected to it.
(GENERALLY, it is the F4 key for HP laptops. That is GENERALLY )
Tap once and no display on external monitor?
Hold the Fn key down again, and tap again on the Display Toggle-Over key.
It could be the laptop IS working, but there is a component, or components, that are bad for the internal monitor of the laptop.
Display doesn't show on laptop's LCD screen.
Could be something as simple as a bad connection of the Video Cable to the motherboard, or to the back of the LCD screen.
Could be a bad Video Cable.
Could be a bad screen Inverter.
Could be a bad Backlight.
For the above; a simple test,
Laptop on use a flashlight, and aim it at the LCD screen of the laptop.
Shine the flashlight at various angles.
Tell me what you see.
An LCD screen does not produce light. It needs an additional light source.
A Backlight is the additional light source.
A Backlight can be a CCFL, or series of LED lights. (Present technology)
A CCFL is a Cold Cathode Fluorescent Lamp.
Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.
(Average size is 2mm Thick, and almost as long as the LCD screen is high.
2mm is a Little more than 1/16th of an Inch, or about the width of this letter -
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