Never seen an A1200 doing this before!

[tone007]

Sounds like whatever makes the power LED light up in dim mode is malfunctioning (power LED is generally supposed to be dim for a second or two on powerup before going bright on a 1200, correct?)

[tone007]

Isn't the power LED brightness level supposed to indicate the status of the low pass audio filter?

Might be multipurpose, like save2600 said, they dim during boot/reset as well.  No idea if the filter is toggling at that point.