[8125, K-JAM, P4300, MDA Vario General] jcostantino:
I'm writing this up because someone else might like to benefit from my experiences with doing this repair.

Get your tools together: Multimeter, Torx T5, jeweler's Phillips (size 00), 15w soldering pencil, a bit of flux, some thin (I used 0.38mm 63/57% tin/lead) solder, and a clean place to work. You may want to grab a small ice cube tray or something similar with compartments to toss the screws in so you remember where they go. I highly suggest you get Kapton (3M) tape but you could use cellophane tape or a cut piece of packing tape. I had Kapton on hand so that's what I went with. You also need to either make sure the seller provides the double-stick tape gasket that binds the digitizer to the LCD shield or that you managed to salvage the one that secured the old digitizer. I was lucky and it came off the glass and stayed on the metal.

First of all, I've always had horrible problems with alignment with my Vario. The top of the screen was usually fine but the bottom would start drifting up. Cleaning the crap out of the edges under the bezel with a business card or doing the thumb rub was fine for that particular session but when I would sleep it and put it in my pocket, it was screwed up the next time. Dropping my Vario on the floor has managed to create a triangular dead zone that peaks at 1/2" from the bottom center and degrades towards the bottom left and right corners.

I bought a digitizer on Ebay from a seller in Hong Kong. It arrived about two weeks later and came with a T8 Torx and a case cracking tool. The T8 was thrown aside because it's obviously the wrong tool so I used my T5 and cracked the case. I won't get into disassembly/reassembly because that isn't the object of this and you can google the directions. Suffice it to say, when you reassemble the back half, ensure the volume slider on the case isn't going to snap the tab off of the volume switch on the board like I did the last time I disassembled it.

A note on this particular digitizer - It's NOT a HTC brand part. It's a generic part and doesn't have the glossy top sheet. I paid $20 shipped and for $20 it ain't bad. There is slightly less light transmitted and it's harder to read outdoors in direct sun but no big deal - it hasn't had to be realigned yet.

Now that you've removed the back cover, lifted out the board, unscrewed the LCD slider from the front cover, disassembled the two halves of the LCD slider, removed the screws that secure the top and bottom button pads to the LCD top frame and lifted out the LCD/button assembly and it's sitting in front of you - lets get to work!

First of all, you need to commit to this before you start making irreversible changes. If you've never soldered before, put this thing back together or find someone who has. You don't need a SMT station or the ability to solder 0605 components but since you're soldering on the plastic ribbon carrier, you need to be sure of your skills in order to not trash the LCD ribbon.

Now that you're ready to do this, examine the LCD panel and you will see that the digitizer is attached to the frame of the LCD panel. Use thin blade like a single edged razor to slide between the glass panel and the metal case and start lifting up the glass panel. If you're lucky, it'll want to stick to the metal case. As you lift the glass, poke in some tooth picks or similar to keep the glass from seating again. Start at a corner and work around going SLOWLY. I got to the bottom, rushed, and smashed the old part causing glass dust to go everywhere!. Try to avoid that.

Now that the old panel is off, cut the ribbon cable going from the base of the digitizer to the back of the LCD. Just slice it in half to get the old part out of the way.

At this point, align the new digitizer at the top of the frame first and then gently press it down. Ensure that ONLY the back's protective plastic sheet has been removed to avoid smudges and scratches. Now place the unit face down on something like a mousepad or similar surface.

There is a piece of Kapton tape across the digitizer ribbon and the backlight ribbon. Peel from the side with the digitizer FIRST! I started pulling from the backlight cable side and damn near pulled the backlight ribbon off!

GENTLY GENTLY GENTLY peel the old ribbon cable from the digitizer DOWN and ensure that it isn't ripping the pads away from the LCD cable. There may be a better way to do this but this method worked for me, I grabbed a corner with needle nose pliers and slowly pulled at a 45 degree angle. You want to pull the top which is the side soldered to the ribbon, not the bottom, which you cut earlier.

Plug that soldering pencil in, make sure it's set to 15w.

Now, with my el-cheapo digitizer, the ribbon from the front was slightly misaligned and I had to angle it over to the right. Otherwise if I went straight up it would've been misaligned about 2mm to the left. Ensure you have the traces parallel and directly on top of the existing ones and tape the bottom of the cable so it stays put. Another thing with my digitizer was the end required trimming. This made it easy to position when I had it bent back.

Now that the bottom is aligned and you don't have to mess with it, bend the cable back so that the copper traces are now facing up. The bend should be at the bottom 3rd of the exposed traces on the LCD cable. Make a nice sharp fold on the cable. Swab on a little bit of flux to make things easier to manage. Grab a popsicle stick or similar to push the new ribbon to the LCD ribbon, get the solder ready, and try to keep the heat on very shortly. You should only need 3 seconds of heat to get a decent solder joint because there is almost zero copper to heat up. Ensure the first joint is good by a quick tug of the cable and do the next three. After they are done, test with the meter going across to ensure the joint is good and from one side to each neighbor to make sure you have no shorts. Do the next three and then cut the extra ribbon cable off leaving maybe 1/4". Grab your tape and put a nice big piece across the back of the LCD covering both ribbon cables just like it was.

Now, reassemble your phone, turn it on, align the screen, and you ought to be good to go.

I don't take any responsibility for anything you might do to screw up your phone. These were my steps to fix my phone and they may not work for you and your phone.

As an aside, the new matte screen doesn't accumulate 'face gunk' quite like the old glossy one did. Also, the sensitivity is down a tiny bit and it needs more finger pressure to use Slide2Unlock. The digitizer also gets Newtonian Rings (google it) whereas the OEM one didn't. Also, there is a faint hum from the backlight (?) when it's on now that I didn't notice before.

So far, so good... The alignment on the bottom right corner is about 1.25mm above where the stylus point is but that might just be a problem with the screen itself. The alignment has stayed rock steady since I aligned it yesterday morning.