Audio Switcher LEDs are too dim

摘要

I recently built the 3-Input Stereo Audio Switcher (January 2012; siliconchip.com.au/Article/821), and the LEDs do not light up; I used Altron-ics S1177 switches. The relays work, and the 5V supply is OK, but when the switch is pressed I get only 0.75 V across the LED (red probe to "A" and black probe to cathode). This works out to about 2.3mA through the LED.