I've replaced some incandescent indicator lights on my vintage amp with LEDs and, after the replacement, the LEDs don't light up. I'm looking for some pointers as to what I could have done wrong. My soldering skills are limited. I've done some soldering of wires inside of my PC (e.g., fans), but I've never done an LED.
My amp is a Yamaha B-4 from 1978. This is a amp that was only available in Japan, but the exterior is visually identical to the Yamaha M-4, the U.S. model.
Recently, the power indicator light burned out and I decided to replace it with an LED so I wouldn't have to deal with this problem again for 20 years. I followed this guide. The guide is in Japanese, but I've linked it because the pictures are useful.
The basics are as follows. The amp supplies 12v to the indicators. The LED I used was 17mA and 3.1v. I soldered in a 560ohm 1/4W resistor into the positive (red) wire and then soldered the positive (longer) terminal of the LED to the red wire and the negative (shorter) terminal of the LED to the white wire. After all that, the LED didn't turn on. I checked all the joints and they look good (i.e. shiny). I then replaced the LED with a different LED and still it didn't work.
Any hints?