Killing the Blues: fun with blue LED phosphors

[Longshan]

My monitors have a blue LED that turns red if there is distortion. I'd love to figure out how to reverse the lights so red is the default.

 

[restorer-john]

My monitors have a blue LED that turns red if there is distortion. I'd love to figure out how to reverse the lights so red is the default.

It's likely an RGB LED. They have four terminals and are either common cathode or common anode. Easy enough to modify to be whatever colour you want. Is it a 3mm/5mm LED or an SMD 'chip' LED?

 

[pjug]

For the curious among you guys, here's the internals of the little LED tester. Notice the active current source.

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Here's a cheap and nasty Chinese Ebay LED 'tester'. The current sources (and markings) are not remotely accurate and passively derived. It's basically useless, although it looks the business.

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Notice the missing (torn off by the screw when being assembled) SMD resistor and the dreadful soldering. Also the resistor values are a mess.

With a 9V battery and a typical RED led, the first three sockets dish out 5mA each. Not 2x2mA and 1x5mA.
The next three with a red LED will put out 10.7mA, not 5mA and 2x10mA
The next five sockets are all the same at 20mA.
And the last two would be 30mA. Actually correct, but only for red LEDs and only with a brand new battery.

For all other colours, you'd need to calculate it all again.

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One of the manufacturers or distributors sent me an LED tester, and I use it occasionally. I never thought much about what is inside the box. I guess I have to take a look now!

 

[pjug]

The problem with blue LEDs is that to get a sane brightness level for a front panel indicator you have to run them at such a low current that variations in component tolerances lead to some being too dim and some too bright. Jason from Schiit Audio once described the problems they had with this, and how they eventually solved it by using plastic light pipes to guide some of the light from PCB mounted LEDs to the front panel.

That's interesting. I use Nichia at work and they seem consistent with constant current drive, even at low current. But maybe other brands are not so and maybe Vf varies to cause problems if you don't drive with constant current. You could also pulse them at low duty cycle, but at extra cost. Those dimming stickers are cheap, though. I would think these manufacturers could find a similar solution, or the pinhole solution. If they really cared. As Schiit did.

 

[Don Hills]

For the curious among you guys, here's the internals of the little LED tester. Notice the active current source.
...

Looks more like a voltage regulator putting out about 7 volts, not a current source?

 

[Longshan]

It's likely an RGB LED. They have four terminals and are either common cathode or common anode. Easy enough to modify to be whatever colour you want. Is it a 3mm/5mm LED or an SMD 'chip' LED?

I have no idea. The monitors are Kalis. I'm afraid to take them apart, but maybe I'll bring them with me next time I visit my parents and see if my dad can figure it out. My studio has a red light theme going on, which is nice in low-light environments, so it would be a great mod.

Thanks for the info!