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KermMartian wrote:
Ultimate Dev'r wrote:
KermMartian wrote:
Ultimate Dev'r wrote:
DShiznit wrote:
I wonder if you can place tiny pieces of paper or cardstock, or another thin material, between each solder so they don't cross each other?


I put razorblades between pins and plenty of flux when I solder super-fine pitched ICs.
Wouldn't the rake-and-bake method be much easier at that point, assuming you're talking SMT ICs?


"rake-and bake" method?
Rake a soldering iron and a small amount of solder across the pads on the PCB. Put the IC roughly in place. Place it toaster oven, heat board, IC will align and joints will properly isolate as the solder melts and beads.


Ah; I was actually referring to applying my method to soldering the pins on the LCD - for actually soldering ICs onto a PCB I use solder paste and a hot air gun Very Happy

DShiznit wrote:
That's exactly what I was thinking. So there's no risk of melting or warping your razorblade?


Nope, but you will get a cool-looking hue to your razorblades after awhile.
Also, if anyone wants to try soldering w/razorblades, made sure you get this type of razorblade, not this (unless you like slicing up your fingertips Very Happy)
Ah, solder paste and a hot air gun is more or less the same, very nice. And as Ult Dev'r said, DShiznit, the melting point of the steel in razor blades is far, far higher than that of solder.
How about some idea of what hot air gum to use?
john massey wrote:
How about some idea of what hot air gum to use?
That's an unrelated discussion, unless you were to actually find a spare TI-84+ to swap the LCD with. You're better off starting with just seeing if smoothing down the LCD ribbon cable will help.
Well I bought the tool and removed 6 screws. I removed both batteries. I am not able to open up the calculator. What am I doing wrong?
john massey wrote:
Well I bought the tool and removed 6 screws. I removed both batteries. I am not able to open up the calculator. What am I doing wrong?
You need to also unscrew the philips screw holding the backup battery cover on. Once you get that off, you'll need to do the follow:

1. Pull off the keyboard cover. Start from the bottom of the calculator and pull off the faceplate.
2. Pull apart the two case halves at the top of the case; there's a latch at the top of the case that holds the front and back halves together. You should now gently be able to pull the two halves apart completely.
When I said I removed both batteries that is backup and AAA.I used a philips to remove the backup battery and it's cover. I removed the faceplate. I put a small screwdriver at the top and pried open the two haves. They seem stuck. Have I missed something or should I just be more forceful
john massey wrote:
When I said I removed both batteries that is backup and AAA.I used a philips to remove the backup battery and it's cover. I removed the faceplate. I put a small screwdriver at the top and pried open the two haves. They seem stuck. Have I missed something or should I just be more forceful
Have you opened it at the top far enough to see the latch at the top? If so, you should be able to gently pry the two halves apart. You'll need to release latches along the side, so also try lateral shearing of the two halves (ie, if the calculator is facing up, move the bottom half left and the top half right).
Now I am in.I see a foil sheet. I lift the sheet and I do not see the display. I assume that I need to get to the other side of the pcb. How do I do dat?
john massey wrote:
Now I am in.I see a foil sheet. I lift the sheet and I do not see the display. I assume that I need to get to the other side of the pcb. How do I do dat?
Excellent. When you look under the foil shield, you should see something like the image on the previous page (this one from Datamath). the PCB controller is on that extra piece at the top, and the black ribbon cable that goes up and over the mainboard to the front is the one that concerns you. There are four small Philips screws holding the mainboard into the front half of the case that you'll need to remove (actually, six, because two of them hold down the foil shield). Be careful not to turn the case over after you remove those screws, because all the keys will fall out, and it will be a pain to sort them all out again.
so on the one side I see the display and on the other side I see the connections to the display Right? What should I be doing now? While waiting for you I broke the display. Game over, I lost Mad thanks for all your help Smile
Oh no, I'm sorry to hear it! Sad What do you mean you broke the display? It might still be something fixable. Also, I'm not familiar with the mother-of-pearl eraser trick, what's that?
The display has a crack in it. If you have a pcb track that is dark you can take a mother-of pearl eraser and rub the effective areas to clean them. I used to have a big one with a sharp edge. Works like a champ!

I sincerely believe that repairing a pcb on a calculator is beyond my skill set. I have very shaky hands.
john massey wrote:
The display has a crack in it. If you have a pcb track that is dark you can take a mother-of pearl eraser and rub the effective areas to clean them. I used to have a big one with a sharp edge. Works like a champ!

I sincerely believe that repairing a pcb on a calculator is beyond my skill set. I have very shaky hands.
That's fair and understandable. Sorry to hear about the LCD crack; I could imagine that it might already have been there. And that's a great tip about the eraser; I'll have to keep that in mind.
*bump* So my TI-83+SE arrived; it has the classic symptoms of ribbon cable degradation, as shown below. Opening it up, it has an 84-style LCD soldered onto an 83+-style LCD daughterboard connected to the main logic board via an 83+-style ribbon cable, which is pretty interesting, and something I had not previously seen. I'm doing continuity/resistance checking on the ribbon cable at the moment.

O_o what is that on the screen? were you running something or is that just the homescreen?
qazz42 wrote:
O_o what is that on the screen? were you running something or is that just the homescreen?
Nope, that's just the normal homescreen with (in theory) the cursor blinking in the top-left corner. Aight, I have fixed this calculator preliminarily, and it's almost completely repaired. I had to replace five wires, plus (to my surprise) the positive power rail. It's still displaying slight problems, so I suspect I missed one medium-resistance line.
wow, sounds really complicated and hard, good luck
heh, the user must have really been screwing with his calc Very Happy
qazz42 wrote:
wow, sounds really complicated and hard, good luck
heh, the user must have really been screwing with his calc Very Happy
On the contrary, it's because TI uses ribbon cables and joints that seem to degrade over a period of years. Sad

Anyway, here's an image from when I had still missed one megohm-magnitude resistance lead:



Here's the final fixed calc after another lead was added. Fully working calculator for $17.49 including shipping, plus 45 minutes of work! Huzzah!

This topic will be invaluable when I attempt my own calculator repairs. Thank you all.
  
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