[sdiy] Glowing diode on Casio CT-510 analog board?

Benjamin Tremblay btremblay at me.com
Tue May 23 02:53:15 CEST 2023


Here it is.
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Benjamin Tremblay

> On May 22, 2023, at 8:41 PM, Benjamin Tremblay <btremblay at me.com> wrote:
> 
> ?Sorry if this is way way way off topic. I?m trying to fix this Casiotone keyboard and there are no schematics. The power supply seems to be putting out around 4 volts. The logic board runs but the 4558, 4066, and power amplifiers seem inert. 
> I?m trying to trace the power supply. Unlike most Casios from the 80s, the 5 volt regulator is just a zener diode, not a 7805. There?s one more non-zener diode on the board, and it?s faintly glowing red (!)
> I know all diodes emit radiation when they are operating, but this one has such and led-red color.
> Were such diodes ever used to indicate an overload on the board? I was more interested in fluorescent hair gel than power supplies  when this keyboard was made. 
> <image2.jpeg>
> 
> (Lower left corner, a normal looking glass diode)
> Benjamin Tremblay


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