Touchscreen 101

Perhaps someone can talk me through how exactly the touchscreen works/is constructed.
As far as I can see the screen in my CF-74 has only the 20 pin connector between the screen and the computer. There is another board taped to the back of the screen that has two connectors but there is no physical connection between that board and the screen!
I have read back through some threads and it implies that the screen is effectively a sandwich of layers. They also imply that the touchscreen component is replacable, so I was guessing that in principle the LCD would also be replacable as a component as well.
Presumably the touch screen is the first layer, so how does the computer get the signals?
How difficult is it to seperate the screen. Is there a tutorial or pics I can reference. I have the service manual and the schematics but would find it easier to understand real world explanations.
Here is the back of the screen. It does like like it is the same 13.3 screen as used in the CF-29 although I don't think it has the protection layer.
Anyway guidance appreciated!

 

To help us, please provide you FULL model number of your laptops: (CF-74XXXXXXX or CF-29XXXXXXX for example)

Thanks

 

It's a CF-74C3BBXBE.
Right I have got my head around the exploded diagrams. Its just a bit confusing until you realise that the sub assemblies are encircled!
It does show the LCD and the Touchscreen and a protective film as seperate items! I have been confused by people saying they have peeled the protective layer off. I can't see how that would be possible until the screen was seperated from the metal frame.
The only component that obviously still works is the backlight!
In case you haven't seen the damage, see the pic!

 

The "protective layer" you are talking about is simply the screen protector. ALL touchscreen models have one. It's sometimes hard to see it but just look at the corners of the screens and you'll find it (unless it was removed )

 

Hmm.. so does this screen protector sit inside the metal frame of the screen? I guess if it could be removed without taking the bezel off then its a posibility! I guess anything could have happened when you are unsure of its heritage.
Using the CF-29 Wiki for the part number would seem to indicate that its not a touchscreen model as the 3 indicates a 13.3 XGA! Yet clearly it is a touchscreen and has the board and the cables. I doubt whether someone has replaced an ordinary screen with a touchscreen. The rest of the letters seem to make sense apart from the HD and Ram.
There is a beater Cf-29MK2 available which is complete. Seems a shame to pirate that just for the screen. Guess I would be taken out and shot for that!
There are CF-74s in Germany that presumably have working non touchscreens but they heve stated they have 14.1 screens. As they are bios password protected and keyboards in German there is little value in them. If he accepted Paypal that might have been the safer option and fits with my policy of taking two broken things and making one working thing.

 

Actually the best replacement TS panel for your unit is the one on CF-73. Also to remind you that TS glass panel is separate from the lcd screen. This is also easy to come off from the front bezel. It is not glued or with double sided tape. The TS panel glass is only attached to the screen by a double side tape from the top and buttom only.


ohlip

 

Right getting really confused here!
Below is a pic of the screen I have removed. To me it looks like a sealed unit. There is nothing attached to the front. There certaintly doesen't seem to be anything like a glass panel or the protective layer on the front. I was assuming all the components were sandwiched in the unit.
It seems to have the touchscreen board on the rear which had two cables on it, one on the bottom and one in the side. The top connector was without any cable. So if that top connector should have a cable connector to the touchscreen then that makes sense - it either never had one, which the model designation implies or it has been removed.
That would also solve the question of how on earth the TS worked without any physical link from the screen back into the computer!
Perhaps Panasonic just made it touchscreen ready. The TS board is readily accessable through a cover on the lid. Seems a bit odd to leave the board hooked up.
I don't really need the touchscreen, so if all I need to do is sort out a regular XGA screen then thats fine.

 

I don't have the information here but the 3 .....74C 3means no touch screen which would add to your confusion while looking for one.
In your first post............the tape in the lower left quadrant???....that is where the tape like ribbon cable would be. Pay attention now **in the models I have seen and destroyed or repaired**. I have never seen your model.
Do this...go to ebay and search for touchscreen element or hmmm??? hold on.... NEW Touch-screen for Panasonic CF-29 Toughbook | eBay Yah here it is for a CF-29. Note the ribbon cable.
The LCD is a separate unit. The touch screen element sticks to the bezel as teo(ohlip) said and the LCD lays on top of it. There would be a PCB where that piece of tape ends. I went back and looked ...the PCB is there but as you said no wires.(from the base of the laptop) The PCB is backwards or upside down from the ones I have worked with but as I stated "never seen one of these".
Now that you are no longer looking for what ain't there let's fix it.

Jeff

 

You might want to have Alex combine your threads. Saves me jumping around so much.

Here's your screen. LCD! Remember the touch panel is separate. You can do as shawn said or order a touchpanel from techtuff or heartland at some point if you wish to upgrade. Panasonic model Laptop Screens

 

Jeff,
That ebay link makes it a lot clearer. I guess I was assuming that the touchscreen itself was integrated into the LCD rather than being an add on.
I wasn't helped by the fact that what I identified as the TS PCB was stuck on the back of the LCD and obviously had connections to the computer with only the top connector unpopulated. Hence my question about how exactly a touchscreen worked as the only direct connection betwen the computer and screen was the 20 pin cable. If the ribbon cable from the TS goes into the TS PCB, which is logical, then it all makes sense.
I have checked the designation in the Setup and the code is the same. I know that "3" also means no touchscreen on CF-72, so will have to asume that the computer was not originally supplied with one but Panasonic in their wisdom fitted the TS PCB and connected it up. That sort of makes sense as the CF-74 has a removable panel on the LCD lid which allows access to that pcb, so it would be relatively straight forward to add one as an upgrade.
Thanks for the link to the LCDs. Always a bit worrying when they don't quote the price. Never good when you have to ask! Again trying to condense what I have found, that particular designation TM133XGA0301-1 doesen't seem common, unless of course its a custom one for Panasonic. Obviously to save any compatibility problems it would be nice to replace like for like. But in order to get some more life out of the machine, I would be quite happy with something that fitted and displayed. I have some technical info on the Torisan displays including dimension so will see what, if any, the differences are.
So thanks for all the comments. My sanity is restored and I can stop looking for a TS that I don't have!

 

Exactly.
As far as the TS PCB on the LCD.
I recently upgraded a 29-L3L to TS and found the wires in place and neatly taped down near the TSPCB...just not plugged in. I:
Cracked the lid.
Rolled LCD out of the way.
Replaced front lense on bezel with techtuff TS panel.
Rolled LCD into place.
Plugged in panel cable with veterinary forceps.
Plugged in taped down wire.
Buttoned it up.
Viola! L3L = LTL 45 minutes max
If you go under the keyboard un-plug re-plug connectors a couple times to do away with corrosion.

Jeff

 

I'll stick this here just in case. Searching for info I have stumbled across this.
The TS on the Cf-74 and presumably other 13.3 equipped models is described as model no MDS-27-2D made by Gunze Ltd.

 

Ok, bit of an ask. Looking at this pic below, is there anything that screams out 13.3 Touchscreen? Waiting for the seller to confirm but the price is good if it is a TS and all functions. Not so good if its just a regular XGA. Then again if its the same screen as my broken one, the TM133XGA0301-1 then might make him an offer on it.
Thanks!

 

You can't tell as touch and non touch look the same on the outside. That pic is of a cf29 which has a 4 wire Fujitsu touch panel. from a Google search the CF 74 uses a 7 wire touch panel. They are both 13.3 but not interchangeable.

Read Ohlip's post. He knows what he is talking about. Find a CF 73 screen. You may be trying to re invent the wheel.

 

Believe me I would like to find any replacement Cf-73/74 parts in the UK! However it would have been a niche market and then factor in the price of everything over here, basically we pay in £ what you might pay in $. Plus it is often the screen that gets damaged in the first place and you see the difficulty.
I have purchased it just out of curousity! Having quickly looked at the CF-29 service manual I can see that components are not common. So the worst case is that nothing, not even the screen is usable but looking at it positively, I will have half a CF-29! Might inspire me to go fully rugged finally!

 

The screamer to me is looking at the screen, Someone has been touching it. Have him read the number off the LCD. (mild sarcasm)
And then 50/50 whether the touch screen works.
Pretend you are bidding on just the LCD. Buy it and then you will need a CF-29 bottom half to go with it and then another LCD which means maybe another half and ..................ad infinitum.

 

Yep! Its looks a bit grubby doesen't it! Could be he just smeared his greasy hands over it. I guess he has just removed the whole lid so I will get the pleasure of opening it up. All part of the learning curve and it might mean I stop asking stoopid questions! However prepare yourself for answering questions about CF29 LCD removal later next week!
Obviously if the LCD isn't the TM133XGA0301-01 then I will blame you for the bum info given on another thread! If it is then I will be content.
That screen must be an oddball. Whether it's to do with the "daylight readable" claim or because its usually behind a TS, I am not sure. Nobody seem to sell the original. There are lots of "compatible" screens, (i.e cheap, nasty replacements) not actual Sanyo/Torisan out there but I would really like to replace the screen like for like with the screen that Panasonic specified.

 

Cf-29htm50bm

 

Drat!
I can see where the confusion arose!
http://forum.notebookreview.com/panasonic/475752-touch-screen-question-2.html
The CF29 has the A01-03 whilst the CF74 has the A03-01.
Comparsion pic below.
As a contigency I might just buy the cheapest Torisan TM133 available to experiment with.

 

I'm doing the same with a CF-51. Updates as they occur. Ignorance IS curable.....but with-out a timeline. I speak for myself.

 

Agreed! Always better to well informed though.
After a bit of digging I can see that I was totally mistaken about it being TS equipped. Having see the location of the TS PCB on the exploded diagram, I assumed that the PCB on my screen was a TS one. In fact it looks like it is actually the TP PCB and thats where a lot of the confusion came from. I also discovered that the unpopulated upper connector of that board is for the WWAN upgrade. The whole detachable panel is on the LCD lid is replaced and the WWAN circuit is attached inside. Thats why it is called the ANT cover! So it all makes sense now!