So yeah, I already mentioned this a few times on IRC but i guess it's better to make a topic...
I played around with powering my TI-89 without batteries and doing so I accidentally connected the polarity the wrong way once, that were 6V and 1.5A.
Ever since that incident I am unable to turn it on again.
It is HW2 btw.
After opening up I don't see any obvious damage on the board..
Any ideas?




Solution:
The fuse needs replacement.
I'd find it very odd if there isn't some kind of reverse polarity protection on the board. After all someone could insert all the batteries the wrong way (not easy but probably doable). I would expect a protection diode or something similar. Otherwise there might be a small SMD type fuse on board. Do you have a multimeter? Can you trace the voltage from the battery to the main board and see where it stops?
Erm i broke my multimeter the same way :[
The TI-83 Plus SE and higher have an SMT fuse (a little white component near the battery contacts) that blows if you force a high reverse current through the calculator. In fact, geekboy and I had some fun experiences with that at Maker Faire 2013, leading me to order a packet of replacement fuses for future use. It's entirely possible that your TI-89 has a similar fuse you can replace or bypass.
the thing that says 500mA? It looks fine to me.
Should I try to overgo it if i am 100% sure i put polarity on correctly?
Sorunome wrote:
the thing that says 500mA? It looks fine to me.
Should I try to overgo it if i am 100% sure i put polarity on correctly?
Unless you put many amps through it, it gives no physical indication (changing color, being burnt, being damaged) that it has blown. If you're absolutely sure you have the correct voltage and polarity, you can try shorting across it and see if the calculator turns on. If it does, you should replace the fuse:

http://www.digikey.com/product-detail/en/0451.500MRL/F2574CT-ND/813052
How many amps is many? Because i sent three times its amount through it >.>

EDIT: This small white F1 thingy on the top, right? https://img.ourl.ca/CIMG4355-small.jpg
Sorunome wrote:
How many amps is many? Because i sent three times its amount through it >.>
You don't send amps; you make amps available. A 1.5A, 6V power supply supplies up to 1.5 amps for the connected load to consume, but if the attached load is an LED with an effective resistance of zero and a forward voltage of 2.1V in series with a 0.25 watt, 330-ohm resistor, then the current actually consumed is:
V=IR -> I=V/R -> I = (5-2.1)/330 = 8.7mA
(and incidentally the resistor dissipates P=IV=(.0087*2.9)=0.025 Watts, 1/10th of the maximum value, but that's neither here nor there).
Sorunome wrote:
How many amps is many? Because i sent three times its amount through it >.>


Did you actually measure the current that went through? You would have probably melt the whole thing. Assuming you didn't apply over the nominal 6Volts in reverse polarity, I would expect the fuse to blow fast enough. And I assumed you haven't seen any smoke coming out? Cool
Tried the bypassing and it still doesn't seem to turn on Sad
Sorunome wrote:
Tried the bypassing and it still doesn't seem to turn on Sad


I think your calc needs a good look from someone with more expertise. Do you have any friend into electronics? If it's anything other than the fuse or some small component before the main ICs, it is probably not serviceable or not worth it Sad
sonic2000gr wrote:
Sorunome wrote:
Tried the bypassing and it still doesn't seem to turn on Sad


I think your calc needs a good look from someone with more expertise. Do you have any friend into electronics? If it's anything other than the fuse or some small component before the main ICs, it is probably not serviceable or not worth it Sad
People usually come to me for such stuff lol

EDIT: Oh, also, i tried overpassing it again and this time it worked, seems like my overpassing the first time didn't had great conductivity Razz
Sorunome wrote:

EDIT: Oh, also, i tried overpassing it again and this time it worked, seems like my overpassing the first time didn't had great conductivity Razz


Ah, that's great then! TIs seem to be indestructible! I would still get the little fuse replaced, it shouldn't be too difficult with a reasonably thin soldering iron tip (and maybe a magnifying glass Very Happy )
Thin solder tip? I'll just solder with my thick one that thing Razz
sonic2000gr wrote:
TIs seem to be indestructible!

Yeah you're right. You can smash them on the floor, kick them, use them as a ball and they still kida works.
Sorunome wrote:
EDIT: Oh, also, i tried overpassing it again and this time it worked, seems like my overpassing the first time didn't had great conductivity Razz
Even if you solder over it, it's still called "bypassing". Wink At any rate, good work, sir! Don't forget to buy a fuse so you can fix it properly.
I replaced the fuse now and now my shiny TI-89 is working again Smile
Muessigb wrote:
sonic2000gr wrote:
TIs seem to be indestructible!

Yeah you're right. You can smash them on the floor, kick them, use them as a ball and they still kida works.


I beg to differ: It's called the TI-80. That calculator is a disaster when it comes to durability. Just dropping a cotton ball on the calc is enough to damage it (ok well, maybe I'm exagerrating, but it will rarely survive being dropped on the floor, even a carpet).
DJ_O wrote:
I beg to differ: It's called the TI-80. That calculator is a disaster when it comes to durability. Just dropping a cotton ball on the calc is enough to damage it (ok well, maybe I'm exagerrating, but it will rarely survive being dropped on the floor, even a carpet).


Strange. It doesn't look much different from the other models. My 92-Plus from 2001 still shows no real signs of wear (except vanishing rubber strips on the cover and bottom)
Why you may ask, am I resurrecting this old thread? Because after trying all the button combos to no avail, I read it and thought the fuse was my issue when my TI-89 Titanium wouldn't turn on.

I took it apart - which was really quite easy to do as I had the proper tiny Torx screwdriver bit- and found it was not the fuse. It was the spring/wire for the - battery terminal. It had moved and was no longer making contact with the pad.

I tested it by jumping the batteries directly to the pads, and the calculator came right up.
Repositioned the spring, put everything back together, and it's working fine!

Well, I didn't get to use my new silicone soldering mat on this job - although it came in handy for holding the screws - but I'm happy the '89 wasn't toast, as I've had it for a long time.

-TRS80
  
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