Re: TI-H: speaker

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Re: TI-H: speaker

For your Info...

The speaker is not a diode! It is a coil of wire and a coil of wire 
doesn't conduct in only one direction. You at least need a diode!


>I figured out what's wrong with the speaker! All you need to do is take
>your schematic and change it as follows:
>
>1. take the transistor COMPLETELY OUT!
>2. solder the clock/data wires right to the - side of the speaker!!!
>3. forget about the signal ground wire (useless)
>
>I reconstructed my cart this way and it works AWESOME! It is still
>amplified, and you don't need a transistor at ALL! Here is the 
explanation:
>
>The red/white (clock/data) wires use reverse logic (0=+5V 1=-?V), so in
>normal mode, they are both at 5V! When you wire the speaker to the 
circuit,
>the red/white wires connect to the NEGATIVE side of the speaker! (This
>seems wierd but is not). This way, when there is 5V at the red/white 
wires
>(- end of the speaker), no current can flow backwards through the 
speaker!
>But when the red/white wires recieve a 1 or a negative voltage, current
>flows from the + battery pole through the speaker and to the negativly
>charged red/white wires! The reason why your previous schem didn't work 
is
>because the signal ground is ALWAYS negative, so current would flow in
>NORMAL mode (you can't just switch the poles of the speaker either, 
because
>ground CAN'T BE POSITIVE!) The only difference between an AMPLIFIED 
speaker
>and a normal (quiet) speaker is that the + side is wired to the battery
>instead of signal ground (more voltage=more VOLUME!)
>
>Please update the schem on your page.
>
>As for your question on consumption levels:
>
>it's not the speaker that changes the brightness of your screen. I have 
had
>the same problems on my calc, even without ANYTHING plugged into it. My
>conclusion is that the batteries cause this. Different batteries screw 
with
>the contrast in many wierd ways. I've tested RENEWALS and had this 
effect
>CONSTANTLY (even during graphing!); also NiCads and alkalines. Usually 
it
>means the batteries are getting old or weak.
>
>>I hope you or someone else figures this out!
>>
>>I'm working on the speaker problem and the NPN or whatever idea might
>>just work, so lets hope we get it working. I have never expirienced 
this
>>hum or buzz or whatever it is, but the cart seens to draw more power
>>when idle than when active, meaning this reverse logic may cause the
>>speaker to remain activated constantly when there is no signal. This 
is
>>a major problem that I need to get fixed.
>>
>>On another note, I have had trouble getting newer carts to work at a
>>reasonable level of sound. They are extremely quiet, so maybe the
>>original is somehow different???
>
>Maybe your potentiometer has too much resistance. On your page it says 
to
>use a 150K potentiometer. I found this to be WAY to much resistance! I 
used
>a 25K potentiometer and it's volume range is PERFECT! (the one I found 
is
>black and the dial is medium sized, so it fits perfectly into a VB 
case!
>I'll send you a scan!)
>
>BTW I made an internal/external battery expander! I love it! I soldered 
one
>wire to each +/- prong inside the calc, then ran them up the side. I 
cut a
>smal hole (3mm x 5mm) just above the battery case. I got a battery pack
>from radion shack and stuck two small strips of velcro up the side. To 
the
>+/- wires, I soldered a two-pin piece of a breakaway header and covered 
it
>in a small blob of hot glue. The battery pack velcro's to the
>back-upperpart of the calc, so it functions as a desk-prop and doesn't 
get
>in the way!


Richard Piotter

e-mail: richfiles@hotmail.com

home page: <A 
HREF="http://www.geocities.com/SiliconValley/Lakes/5081/Richfiles.html">The 
Richfiles</A>

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