My TI-83+ won't turn on, and when it does, there is just a line across the screen that slowly fades. When you press [2nd] [On] it comes back, then fades again. When I do the take out battery and hold delete thing, all it has is a conjumbled screen. It worked on and off for a few days, but at the moment it is not functioning. I do not have a link cable, so I can't resend the OS. I have tried [on]+[clear], and it does nothing. The last things I did were playing around with hexadecimal assembly and such. I did accidentaly leave it under my pillow, and a friend said it might be a hardware problem with the LCD.
I have tried about a hundred hard resets, and I even left out the batteries overnight. I am getting 50 bucks, so i will buy a silverlink (and ti-82!) off of ebay soon, but that won't be for a while. Please Help!!!

Welcome to Cemetech, ghest1138. It could be the OS, it could be the screen, and it could be static shock. Let's go through some methodical steps:
1) Take out one AAA battery (take out the backup battery too)
2) Mash [ON] a few times.
3) Hold [DEL], mash [ON] a few more times.
4) Hold [DEL] and insert the fourth AAA battery with [DEL] still held.
5) Tap [ON] a few times, then release [DEL].

What happens?

I don't have a backup battery . When I do all that, after I put in the last battery, it displays the "Waiting... Please install calculator software now" message, (not jumbled this time, but at a high contrast) then when I tap on, It switches to the "ERROR! press any key to turn unit off, then turn unit back on", then it turns off because I am holding [DEL].

After you've followed the steps correctly to the point that it tells it is "Waiting...", do nothing. At this point, if you've done [ON] [CLEAR], you've wiped the whole flash except for page 00h. All you can do now is wait for your cable, or find a friends and send over his (1.14-1.19 is preferable.).

you mean press [on]+[clear] while it says "Waiting..."?

Good! This means that you can now use a unit-to-unit cable to load a fresh operating system from a friend's calculator.

I'll try and see if any of my friends have one... Any idea what causes this sort of problem?

It sounds related to the fact that you were messing around with ASM. It's very difficulty to accidentally write to Flash, but not impossible.

Yeah.. I probably crashed it way too many times(forgot to put C9 at the end). Is it possible for this to be caused by temperature fluctuations?

Unlikely, unless your calculator's soldering was so poor that connections broke with board shrinkage/growth associated with temperature fluctuations. Also, I've only heard of that with extreme heat rather than extreme cold.

Definitely not hot here! I checked the LCD's flex cable connections, and they all seem to be fine, except the 5th one from the right seemed a bit off. I might be wrong though, as I don't have much electronics experience.

If you saw the message requesting an OS without any distortion, then it's likely fine. We can deal separately with worrying about LCD connection resistances if you find that you still have problems after loading an OS from a friend's calculator.

okay. Like i said, I'll try and find a friend with a link

Your calculator is most likely fine, just resend your OS, bud.
I've experimented with a calculator exposed to different extremes. The LCD stops responding at around -5 degrees Farenheit

Is it possible to build/scavenge your own unit-to-unit link cable? If so, what do you need to do so? I would rather have my own than have to borrow one every time I need a cool program(Mimas IDE!)

Yes, a unit-to-unit link cable is nothing more than a 2.5mm stereo headphone cable. The connectors on some cables might not physically fit all the way in the calculator port, but usually you can file or cut away a bit of plastic around the connector to make it fit.

You mean file away on the headphones plug? or on the link port?

The plastic around the plug on the cable is often too wide, so we recommend cutting (or even pencil-sharpening) it down.

Sorry, but I don't quite get it. do you have a pic? I have only 3.5 mm headphones to take apart.

That won't work; you can't convert a 3.5mm plug to a 2.5mm plug. Your local RadioShack might have 2.5mm plugs you could use, though.