# Front panel (case) LEDs - 5v or 12v?

#### MichaelD

##### Lifer
I think the LEDs on my brand new case are dead. I want to test them directly with a bench PS, but I don't want to blow them. Are they 5v or 12v? Thanks.

#### JSSheridan

##### Golden Member
LED's usually turn on between 0.6v and 1v, and they only turn on if the voltage is the proper polarity. So if they don't work the first time, switch them around. You can use either voltage when you test them, but I'd put a resistor between the source and led. A 500 to 1000 ohm resistor should be fine. Peace.

#### MichaelD

##### Lifer
Thanks for the reply. I have tried reversing the connector on the mobo pins. I've even tried putting the Power On LED on the HD LED connector and vice versa. Nothing.

The Power/Reset/Speaker all work though. I'm betting the LEDs are dead. If so, I want to switch them out with LEDs I have sitting around.

Why the resistor?

#### JSSheridan

##### Golden Member
To limit the current.

#### MichaelD

##### Lifer
I don't have any resistors laying around. If I hook them up to a 6v supply directly, will they blow?

#### JimPhelpsMI

##### Golden Member
Hi, Leds run at 2.2 volts. They can be used at any voltage as long as the correct resistor is used to drop the excess. Usual current is about 10 to 20 mils. Ohm's Law assuming 5 volts: 5-2=3, 3/.02=150 Ohms. Polarity is essential but reverse wont hurt anything. The resistors are built into the mother board. A meter across the pins on the MB will read about 5 volts. No current = no drop. Jim

#### MichaelD

##### Lifer
Originally posted by: JimPhelpsMI
Hi, Leds run at 2.2 volts. They can be used at any voltage as long as the correct resistor is used to drop the excess. Usual current is about 10 to 20 mils. Ohm's Law assuming 5 volts: 5-2=3, 3/.02=150 Ohms. Polarity is essential but reverse wont hurt anything. The resistors are built into the mother board. A meter across the pins on the MB will read about 5 volts. No current = no drop. Jim

Thanks Jim. I have a VOM; I'm going to check the pins out first. BRB.

#### MichaelD

##### Lifer
The pins on the motherboard read 1.5v exactly. I tried attaching the LEDs to a 1.5v AAA battery; nothing.

What does this mean?

It means my motherboard is defective. I attached the case's LEDs to a 5v bench supply. Every single one lights up. Which means my \$250 motherboard is defective.

Sonofabitch. :| I got such great OCing results with it too. I can either RMA it and hope I get a good board or live w/it.

#### incinerate55

##### Member
you didn't happen to have the MSI k8t neo2 motherboard did you.. because im having the EXACT same problem.. may have to RMA

#### JimPhelpsMI

##### Golden Member
Hi again, 1.5 volt battery might cause the LEDs to glow dimly and really should have some resistance in series. The LED connectors on the MB should be showing close to 5 volts with nothing connected to them and about 2.2 connected properly to LED. 1.5 probably indicates the led pluged backward. Jim