Cupcake? Heresy? Pony? 4 stacks of plexi?


What's up, Doc?
Oct 31, 2016
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Need new pilot LED for tuner.

5mm pilot LED failed open.
Original voltage of LED unknown.
Voltage across failed LED measures 9.5V.
390 ohm current limiting resistor in series.

5mm LED avallable in 3V, 5V, 12V.
Could get one of each and start with highest.
Try until correct brightness without burning out.

Thinking 5mm 3V replacement LED should work.
LED are current driven, not voltage driven.
Current is same everywhere in series circuit.
IIRC all LED's operate at around the same forward voltage, the difference was always in the limiting resistors as to how much juice they could take.

I've put them on a 120 mains line years ago to monitor the functioning of UV bulbs in a hospital air purifier.

Back when I used to build them :thumb:

So do the replacement LED's have internal resistors supplied with them?

I would guess the 12V would give a subdued glow, like a light with a dimmer. Could be what they were after originally..

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