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That picture is awesome! How does Mario Pong play on those six? Just as well as four?

qazz42: If you want cheap calculators, you'll have to find the time to fix them or use their parts. And Kerm usually does both to one calculator Razz

He'll take a part from one and put it in second so the second one works again.
comicIDIOT wrote:
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That picture is awesome! How does Mario Pong play on those six? Just as well as four?
I'm short eight AAA batteries of trying. Laughing I'll probably try to get them on Monday. Smile I have a few other calcs to try fixing to perhaps expand it even further.

comicIDIOT wrote:
qazz42: If you want cheap calculators, you'll have to find the time to fix them or use their parts. And Kerm usually does both to one calculator Razz

He'll take a part from one and put it in second so the second one works again.
Exactly, and it's non-trivial. The cheap calculators I buy are almost all broken, and it takes my EE and calculator knowledge combined to fix maybe 40-50% of them; the rest are writeoffs for experiments, parts salvaging, and Ultimate Calculator prototypes.
That "non-trivial" gets me every time! So, it's not easy? I don't think I'll ever get over the fact that Trivia = Difficult and Trivial = Easy.
comicIDIOT wrote:
That "non-trivial" gets me every time! So, it's not easy? I don't think I'll ever get over the fact that Trivia = Difficult and Trivial = Easy.
Haha no, definitely not easy. For example, I have one calculator that has a glitchy display. It's a TI-83+ with display issues that look like those from an un-ALCDFix'd TI-84+, but of course the 83+ doesn't have the type of screen that can even accept ALCDFix-type commands. I measured the resistances of each of the 17 traces in the ribbon cable connecting the LCD and the mainboard, and found that some were around 7 ohms but others were in the 100Kohm range. I ever so carefully added wires bringing some of the high-resistance ones, and it helped, although the LCD is still not 100%.
>.< That sounds beyond difficult. Eventually I hope I'll be able to do something like that *and* understand why it was done the way it was ^^
_player1537 wrote:
>.< That sounds beyond difficult. Eventually I hope I'll be able to do something like that *and* understand why it was done the way it was ^^
I should post up some photographs and descriptions of some of my fixes and why they work; would people be interested in that kind of thing?
That sounds like it could provide some interesting macro photography options. Not unlike this problem I've not managed to fix for many months.
DrDnar wrote:
That sounds like it could provide some interesting macro photography options. Not unlike this problem I've not managed to fix for many months.
Yikes, what happened there, DrDnar?
KermMartian wrote:
_player1537 wrote:
>.< That sounds beyond difficult. Eventually I hope I'll be able to do something like that *and* understand why it was done the way it was ^^
I should post up some photographs and descriptions of some of my fixes and why they work; would people be interested in that kind of thing?


I definitely would, since I'll be working on broken calcs for school and I could greatly benefit from your experience and tutelage.

KermMartian wrote:
DrDnar wrote:
That sounds like it could provide some interesting macro photography options. Not unlike this problem I've not managed to fix for many months.
Yikes, what happened there, DrDnar?


Looks like my flash drive after playing Hitman off it for several weeks...
DShiznit wrote:
KermMartian wrote:
DrDnar wrote:
That sounds like it could provide some interesting macro photography options. Not unlike this problem I've not managed to fix for many months.
Yikes, what happened there, DrDnar?


Looks like my flash drive after playing Hitman off it for several weeks...
Ah, I bet you're totally right about that being a flash drive.

I'm quite thrilled about this breakthrough in calculator repair because over the years I've always assume that the blank LCD problem (where if you power on the calc, the LCD powers on as solid black) was a hardware failure of the LCD controller chip. Realizing that it's reparable by replacing or augmenting the ribbon cable totally changes the game as far as buying broken calcs and repairing them. I just hope no one tells the As-Is/For-Parts calculator sellers on eBay.
In response to that very awesome photo, how far away are you from the sentient calculator cluster that takes over the world and turns us all into organic batteries?
DShiznit wrote:
In response to that very awesome photo, how far away are you from the sentient calculator cluster that takes over the world and turns us all into organic batteries?
Thanks, and I'm hoping to not recreate The Matrix out of calculators. Laughing Now that I have this nice robust calculator testbed, I need to finish (and indeed, start) documenting the CALCnet protocol and figuring out how I'm going to cram 1k of CALCnet protocol into the 600 bytes of free space that I have in Doors CS.
I don't think the Quarians were trying to wipe out their own race when they started networking computers either...
DShiznit wrote:
I don't think the Quarians were trying to wipe out their own race when they started networking computers either...
Nor the Twelve Colonists in networking the systems of their Battlestars. :/ But it seems to often happen.
When you have a calculator on your operating table, would you consider cutting the Z80's /RESET pin and pulling it high via a resistor? (Fiddly work, but it's at the edge of the chip at least). When the calculator's RAM execution protection kicks in it asserts the /RESET line, and I'm wondering if it could be disabled by that simple modification.

I'd try this myself but I've only got a single calculator and don't really wish to risk damaging it, but if you're dealing with an already-abused calculator it may make an interesting experiment.

(I don't know if this has been tried before. It may have been, but I haven't been able to find anything on it).
Sure, I'd be happy to! I have a pair of calculators that I need to swap the LCDs on (one has a dead LCD, the other has a dead mainboard), so I'll see what I can do when I'm working on that. That would be awesome if that was enough to fix it. Do you know of anything else that uses the /RESET line? Does a RAM Clear touch it?
I don't believe so, I think that is entirely a software feature (though I could be mistaken).
benryves wrote:
I don't believe so, I think that is entirely a software feature (though I could be mistaken).
I guess we'll find out! Laughing I notice that one of the two calculators has the combined CPU/ASIC package, while the other has the discrete CPU, Flash, RAM, and ASIC, so I hope it's the discrete one that's currently functional. Smile I grabbed the Zilog Z84C0006FEC datasheet from, of all places, Digikey, so now I know which pin to cut and pull high: pin 23, the bottommost pin on the right side of the package.

http://www.zilog.com/docs/z80/ps0178.pdf
Well, the right pin on the top row in your photograph, I think? Smile I tied a small amount of wire-wrap wire around it and passed it through the link port so I could probe it. I'd do that to ensure you had the right pin before you try it - I used ?&C000=&C9:CALL&C000 in BBC BASIC to show the pin pulse low briefly to reset the calculator.
benryves wrote:
Well, the right pin on the top row in your photograph, I think? Smile
A good point, I meant relative to the pin-1 dot being in the upper-left corner as it was in the datasheet. Smile The rightmost pin in the top row as per the orientation of the chip on the calc's mainboard indeed, though. I see that it goes directly to the third pin from the top on the left side of that nefarious TI bus manager etc ASIC, but I'll probably try to desolder the line at the z80 since it's nicely situated at the edge of the chip.
  
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