Great, thanks! The transformer of my CA-810 is also humming loudly. I will try this!
About the LED's: I have exact the same problems with diffuse LED's in my B-2 and CA-810. Running respectively on 15 mA and 20 mA. They start to fade slowly and are completely dull after a month's use. I went back to the seller and he said that while you limit the nominal current, the peak currents in 'vintage audio gear' can be much higher. These peak currents would only be visual with a scope. So he said. Apparently these LED's can't handle those peak currents and will die. I'm not sure about his story.
I use LED's from led1.de for years in my gear (sometimes even at 25 mA) and they never fade, even after years of use.
So I think there might be differences in quality