Brian gt chip amp power supply?

guycom · 28th September 2008, 09:04 PM

Hi, Looking for some help. Power supply is done using a centertap 3wire output transformer with help from the picture with diod reconfig. I am getting 17.8 volts output unloaded with no light from the led. Pulled and rotated led to change polarity no light. As always thanks for you help,
Guycom

wakibaki · 28th September 2008, 09:27 PM

LED is dead if you have voltage at its pins and no light either way.

w

guycom · 28th September 2008, 09:32 PM

I understand. Are there different values for leds?
Thanks Again,
Guycom

guycom · 28th September 2008, 09:35 PM

I am reading .3 volts dc at the led.
Regards,
Guycom

wakibaki · 29th September 2008, 09:57 PM

The LED is probably dead short-circuit.

LEDs run RED ~1.2 -> 3.6V BLUE depending on colour and how hard driven.

Take the LED out of circuit. Measure the voltage at the pads. You should see the full supply voltage or at least a substantial voltage depending on the exact circuit. If this is the case the LED is definitely dead, if not you have an open circuit somewhere.

A small lithium button cell is good for quick testing LEDs without a resistor. They can drive even a blue LED, but cannot deliver enough current to destroy.

w

28th September 2008, 09:04 PM	#1
guycom diyAudio Member Join Date: Nov 2006	Brian gt chip amp power supply? Hi, Looking for some help. Power supply is done using a centertap 3wire output transformer with help from the picture with diod reconfig. I am getting 17.8 volts output unloaded with no light from the led. Pulled and rotated led to change polarity no light. As always thanks for you help, Guycom

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28th September 2008, 09:27 PM	#2
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	LED is dead if you have voltage at its pins and no light either way. w

28th September 2008, 09:32 PM	#3
guycom diyAudio Member Join Date: Nov 2006	I understand. Are there different values for leds? Thanks Again, Guycom

28th September 2008, 09:35 PM	#4
guycom diyAudio Member Join Date: Nov 2006	I am reading .3 volts dc at the led. Regards, Guycom

29th September 2008, 09:57 PM	#5
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	The LED is probably dead short-circuit. LEDs run RED ~1.2 -> 3.6V BLUE depending on colour and how hard driven. Take the LED out of circuit. Measure the voltage at the pads. You should see the full supply voltage or at least a substantial voltage depending on the exact circuit. If this is the case the LED is definitely dead, if not you have an open circuit somewhere. A small lithium button cell is good for quick testing LEDs without a resistor. They can drive even a blue LED, but cannot deliver enough current to destroy. w

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