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PostPosted: Mon Aug 14, 2017 5:29 pm 
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Location: Seattle
Cyber Akuma wrote:
I was just asking if there was any particular reason I was not aware of that one would have used a potentiometer instead of a rheostat because a rheostat would not have worked for whatever reason.
No, both the potentiometer (so named because it originally meters the potential (=voltage) by dividing it) and rheostat (so named because it holds static the ... uh, well, flow, a kinda gross cognate is "diarrhea") would work here.

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It's really more of a "nice to have just in extreme cases" thing, I was more concerned if it would cause any issues to do it. This is going to partially also be a learning experience for me (No, I am not just going to blindly solder onto my NES without a lot of practice on junk first) hence why I wanted to do it, I just like having the potential option.
I understand. I'm just saying that there functionally no such case, not even an extreme one.

My caveat about "breaks an original (US) Nintendo World Chanpionship or (Europe) Nintendo World Cup +SMB+Tetris" is specifically only in the case of removing the CIC lock altogether; both of these cartridges rely on the CIC +RESET signal which remains functional if the CIC lock's pin 4 is modified.

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Ok, good to hear. So then basically no audio mod I do could run the risk of causing issues with the hi-def NES?
Not unless you break things.

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Or am I completely misunderstanding what diodes are for?
Yeah. Diodes allow current to flow in one direction. They don't block signals, only power. After all, you can still make logic circuits out of them.

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I just have to unplug the HDMI cable from the back of the NES to get composite working again?
[...]
this means that neither the interposers of the hi-Def NES that sit between the CPU/PPU, nor the CPU/PPU themselves get permanently soldered to anything can can be easily removed?
Everything I have seen kevtris et al. say state that both are the case.


Last edited by lidnariq on Mon Aug 14, 2017 5:33 pm, edited 1 time in total.

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PostPosted: Mon Aug 14, 2017 5:32 pm 
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Formerly WheelInventor

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Location: Gothenburg, Sweden
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From what I understand, a potentiometer is basically a rheostat with an extra fixed output (From what I read, a rheostat would have two connections would a potentiometer would have 3), that I would need to do some extra work to bridge to basically make it work as a rheostat instead.


There's no extra work. All you need to do is not connecting one pin. When all three are connected, a potentiometer works like avoltage divider rather than a variable resistor.

Depending on what pins you connect in "rheostat mode", you can get "turn left to lower volume" (conventional) or "turn right to lower volume". Again, you should get an audio/log/nonlinerar pot to get a natural sounding curve when turning the volume up and down. Those are all names for the same thing - they can be listed differently depending on manufacturer on sites like digikey, mouser, etc.

Full article here.

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http://www.frankengraphics.com - personal NES blog


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PostPosted: Sat Aug 19, 2017 11:24 am 
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Joined: Mon Aug 14, 2017 4:02 am
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lidnariq wrote:
Yeah. Diodes allow current to flow in one direction. They don't block signals, only power. After all, you can still make logic circuits out of them.


Yeah, I know they are used in logic circuits, but what do you mean that they don't block a signal? Would a diode then not help much in protecting the CPU if I do the stereo mod? I am still going to add capacitors for protection regardless.

FrankenGraphics wrote:
There's no extra work. All you need to do is not connecting one pin. When all three are connected, a potentiometer works like avoltage divider rather than a variable resistor.


So I don't even need to connect the third pin of a potentiometer to anything if I want to use it like a rheostat?

So then, if I don't have either any rheostats or potentiometers on me, would it matter at all which one I get for this project?

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Again, you should get an audio/log/nonlinerar pot to get a natural sounding curve when turning the volume up and down. Those are all names for the same thing - they can be listed differently depending on manufacturer on sites like digikey, mouser, etc.

Full article here.


VERY informative to know, thanks!


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PostPosted: Sat Aug 19, 2017 3:29 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
Cyber Akuma wrote:
but what do you mean that they don't block a signal? Would a diode then not help much in protecting the CPU if I do the stereo mod? I am still going to add capacitors for protection regardless.
Diodes allow current to flow in one direction. That's what they control.

They don't control signals like "true" or "false" or "high" or "low" or "1kHz sine wave".

If you're specifically asking about adding overvoltage protection diodes... yes, you can do that, but you may not need to depending on the rest of your circuit.


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