TI83+ graphing calculator

[back&forth]

My girlfriend and I each have a broken TI83+ graphing calculator. One night I boasted that I bet I could fix both of them; she laughed and said that she didn't think so. Anyways, long story short: we have a very lucrative bet going on now. This is not about money, or if it is "worth it" to fix these. I NEED to win this bet (if you get my drift.) I've got good soldering skills so that won't be an issue. I need advice where to start. I'm fairly lost with these surface mount devices. I've attached a high resolution scan http://www.imagebam.com/image/978df4175166479 of the PCB and greatly appreciate ANY and ALL suggestions. Thanks in advance!

[Toasty]

Re: TI83+ graphing calculator

Well....

What's the problem? You've given us nothing to go on.

[back&forth]

Re: TI83+ graphing calculator

Wow, I'm an idiot. When powered on, one does not respond/turn on at all and the other has a completely black screen (as if all pixels are turned on.)

Is there anything else I can tell you?

[shadow]

Re: TI83+ graphing calculator

Have you tried the obvious first? On my TI83 (not TI83+), whenever I change the batteries, the contrast/brightness of the screen is set way low. I always have to bump up the contrast when changing batteries. Without bumping up the contrast, it seems like it's dead. That is, nothing is displayed on the screen and there seems to be no response from anything you press (mainly because you can't see anything on screen).

[back&forth]

Re: TI83+ graphing calculator

Yes. I checked this and did the hardware reset key sequences. Unfortunately it didn't do the trick. Good advice nonetheless.

[shovenose]

Re: TI83+ graphing calculator

Were they dropped? Liquid damage?
I have a feeling it didn't just die one day.
What happened to them?

[severach]

Re: TI83+ graphing calculator

I see the boards are different. That means you won't be swapping any chips. The ribbons look like they are glued on with anisotropic paste so you won't be swapping those.

I think this one will be won by subterfuge. Buy two new calculators and put the guts into the old cases. Be sure to fix them at different times so it looks like you're hardly working--I mean working hard.

[lti]

Re: TI83+ graphing calculator

At minimum contrast, there will appear to be nothing on the display. At maximum contrast, it will look like every pixel on the display is turned on. It appears that you checked the contrast already. Maybe you could look for any activity from the CPU or the custom chips. I don't know what activity the custom chips would produce, but the one on the right has a standard Z80 CPU.

Also, Imagebam was the first image host I encountered that attempted to download malware onto my computer. I am not going to open that link to see if that still happens.

[back&forth]

Re: TI83+ graphing calculator

Severach: I can't cheat. She want's to watch me fix them.

Shovelnose: She says she never dropped hers and I know for a fact that mine was well taken care of and never had any issues with liquids or drops. As for mine, one day it just wouldn't turn on any more. She claims the same happened to hers with the black screen.

Iti: I'm more than willing to host the pictures any place you feel safe. I use imagebam a lot because it doesn't require an account and holds a fairly large size image. I wanted to be sure to preserve the detail.

What about replacing the capacitors with new ones? Can anyone help me identify whats what on this board and where they are at. I can start there and if I don't succeed I can move onto the chips next.

[digge]

Re: TI83+ graphing calculator

I think this might be a tough nut to crack, never owned the ti83 myself but had the ti82. What i would try would be to clean them both out with some kind of alcohol and see what that does. Maybe some moist got in there somewhere, just shifts between hot and cold can do that. Just be careful and make sure its completely dry before you try them.

[kc8adu]

Re: TI83+ graphing calculator

dead one check f1.its on the left near the bottom.its a fuse and gets blown from the wrong wallwart.
backout would be a contrast adjustment.

[bluto]

Re: TI83+ graphing calculator

No wall wart on these. Battery only. The connector on the bottom is to link two calculators together to copy data...er..games rather between them. Checking F1 would still be a good idea. I am going to take the position that there is not much you can do with these especially being a beginner. My mantra when I start to work on something is this.... 'The silicon parts rarely go bad especially on their own'. So that probably rules out the big chips. And given that this is a battery powered device and not an inverter section of an LCD monitor, the little SMD diodes and transistors are probably not bad either. Of course it could be a bad ROM chip, but with that you are probably screwed unless you could transplant a good one off an identical dead calculator. So other than that it could possibly be a bad crystal, or maybe even a bad SMD capacitor or resistor. So check all of these. If I remember back to my youth and the halcyon days of the TI-85, there was a howto on overclocking it by replacing one of the timing capacitors. You didn't attempt anything like this I hope. An of course the last possibility is bad solder joint(s).

So yeah, this was not a good bet to take. Let your next one be an LCD monitor with bulged capacitors and you will have a lot better shot at winning.

[ratdude747]

Re: TI83+ graphing calculator

ive had one die... dead, nothing would bring it back.

(luckily it wasn't my calc...)

[mockingbird]

Re: TI83+ graphing calculator

The problem is the flex cable between the PCB and the LCD... Check this guy's video out which I coincidentally saw last week:
http://www.youtube.com/watch?v=aIlR0LpeXng

[ratdude747]

Re: TI83+ graphing calculator

The problem is the flex cable between the PCB and the LCD... Check this guy's video out which I coincidentally saw last week:
http://www.youtube.com/watch?v=aIlR0LpeXng

Not a universal fix. I saw and tried that on my dead one and it didn't fix things.

if your display is garbled, yeah, but if it is dead (as in no response at all), then no.

[bluto]

Re: TI83+ graphing calculator

I can also vouch that the screens are problematic. Here is my trusty TI-85 and also a TI-82 that I picked up at a yard sale for 75 cents. The TI-85 has 3 dead horizontal lines (as a result of letting my sister borrow it) and the TI-82 has 3 or 4 dead vertical lines (as a result of leaving it in the cold garage).

The 85 didn't seem fixable. No ribbon cable just the rubber mat connection between the glass and the board. The 82 probably has a ribbon but I haven't cracked it open yet.

[cmj21973]

Re: TI83+ graphing calculator

I think this might be a tough nut to crack, never owned the ti83 myself but had the ti82. What i would try would be to clean them both out with some kind of alcohol and see what that does. Maybe some moist got in there somewhere, just shifts between hot and cold can do that. Just be careful and make sure its completely dry before you try them.

Give these a shot.

http://www.ifixit.com/Answers/View/6...3+wont+turn+on

Clean battery contacts and connector pads with rubbing alcohol 70% or higher. Also clean keypad contacts.

[back&forth]

Re: TI83+ graphing calculator

kc8adu- I checked the fuse, there's continuity on both.
Diggie- I cleaned them both with rubbing alcohol (90%)
bluto- I didn't try and mods but I would be willing to change out the resistors and capacitors. I'd greatly appreciate if anyone could help me identify them - with the SMD devices I am really lost.
mockingbird- That's really interesting. I didn't come across that video in my google research. I tried testing the resistance and it doesn't appear to be my problem. Great advice though!
CMJ21973 - I tried all the steps on those pages (many before I posted here too) and there's no luck. I'm fairly confident something's gone wrong on the PCB.

I wan't to take some time out to thank everyone here, I greatly appreciate the help!

Would the blue ESR meter help me find bad capacitors on these?

[ben7]

Re: TI83+ graphing calculator

You should get circuit diagrams of these, and check the voltages of power rails.

-Ben

[b700029]

Re: TI83+ graphing calculator

Do you have a scope or an LA? The one on the right has a discrete CPU (it's probably an older revision) so you could check if there is any activity on the address/data pins, and that the clock inputs are OK.

As for schematics... a quick Google search proved futile, but a hint I got was to get the FCC ID (if there is any) and look that up on the FCC website. You might be able to find schematics there.