Re: TI-H: Turboing/TI-82 SWITCH WORKS!!!


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Re: TI-H: Turboing/TI-82 SWITCH WORKS!!!



>I used some extra long wires because I installed my turbo swich on the 
>wrong side (all the wires have to be on the same side if you install a 
>SPinTerface port), so the wires had to wrap back over themselves. I also 
>have a solder joint between the wires. I know it works because I actualy 
>did this and it RUNS!!!
>
>The fact that the TI-82 isn't supposed to run on less than a 15pf 
>capacitor and sometimes requres a higher one may mean that stray 
>capacitance in wires may be higher than we possibly thought it was!!!
>
>I hope the TI-82 turbo switch can be recreated. The wires connect to the 
>two terminals of the old cap location and it runs to the left side of 
>the calc, raised to right below the memory chip. It goes to the other 
>side and conects to the switch at the left end of the back case when 
>laying open The switch is a large one, layed sideways. The cap connects 
>to the middle and top pin. the top and botto pins have the two wires 
>connected. The bottom pin and the middle have nothing between them. 
>There is a 1.5-2 inch wire between the switch and the other wire. The 
>wires are soldered together about a third of the case width from the 
>left. I am not sure if this is important, but It crashed with C7 
>removal, screwed up the screen with 2 inch wires, and runs great on the 
>doubled over wires.


First of all, the RC time constant for the 82/85 is probably not based
solely on that capacitor!  For one thing, the speed is probably based
mainly on some other internal capacitance, and C9/C7 (whatever) is
just a trimmer, so the difference between 1 pf and 30pf ain't that
much, and that's why you can often just leave it out.

Secondly, if long wires are making the difference, then it's likely
not stray capacitance but rather *inductance* that's causing the
speedup.  Inductance is a whole other bag of worms compared to
capacitance (usually reserved for 2nd year electronics courses) but
they can cause similar effects.  Also note that those wires will
probably double or triple the stray RF noise that your calculator is
generating which can wreak havoc for RF equipment nearby.  Other than
that your findings are quite strange...

-Mel
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The TI-Memory Expansion Homepage
-http://www.egr.msu.edu/~tsaimelv/expander.htm


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