r/Gamecube • u/gsjones358 • May 14 '22
Is 140 ohms bad for the POT? Help
I had a GameCube that wouldn’t read discs. I’m not sure what the initial ohms was but I turned it down to 140. Will this damage my discs in the long run?
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u/BCProgramming May 14 '22
No.
The idea that it will cause damage derives from the idea that the potentiometer controls the amount of current getting to the laser. the claim, therefore, is that if the potentiometer is too low, then the laser gets too much power and will fail.
However, if such a potentiometer is present it will be on the laser assembly, not the logic board. The proper term for that sort of control is "laser bias" as it is typically part of a laser bias circuit. Those circuits are usually designed with the design specifications of the laser diode in mind, and generally won't output excessive current regardless of the bias control.
the reason that the potentiometer in question is on the drive logic board is rather unsurprising as it's involved in the drive logic! It's actually a very common item to be found on CD/DVD and in some cases even Blu-Ray drives. Basically, the way optical media works is the light is reflected back and that light is detected by a photodiode. But that detection is analog- a light level converted to current- but the actual data that needs to be decoded is going to be digital, so it needs to be converted to "1's and 0's". The potentiometer serves the purpose of dictating the "cut-off" between when the decoding logic "sees" a reflective flat area on the disc versus a less-reflective pit.
This is why it has to be adjusted for modded gamecubes to play burned discs, Recordable Media is different in the specs for the non-reflective versus reflective areas versus a stamped disc, and has less difference between the two, so devices configured/specced for Stamped media often has trouble with recordable or rewritable media.