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

NT nathan at idmclassics.net
Wed May 24 01:13:00 CEST 2023


Yes these are used in both Polysix and Poly61 to show active voices. I
noticed them in something else recently but don't recall off the top of my
head - a similar age poly.

Nathan

On Tue, May 23, 2023 at 3:52 AM Roman Sowa <modular at go2.pl> wrote:

> If it glows, it is LED.
> Those kind of early LEDs were used at least in one of the Korgs, Maybe
> Poly6 or Poly61, can't recall now, to indicate active voice.
> I was shocked too when I saw them first.
>
> Maybe it's there just to make some cool light, but knowing early
> japanese designer's practice of cutting corners, this was probably used
> as voltage reference.
>
> FWIW, back in the 90's I used 4 LEDs to create expo converter to drive
> VCF. Turned out to be accurate enough for the filter. And it looks so
> cool when played, especially with deep LFO. Too bad I have to open the
> case to see it.
>
> Roman
>
> W dniu 2023-05-23 o 02:53, Benjamin Tremblay via Synth-diy pisze:
> > Here it is.
> >
> >
> >
> >
> > 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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