My Buffalo has been working fine for nearly a year when I noticed the sound was becoming coarse and strained so I decided to do a health check on the power supply first.

I have two single placids running the DAC and a Placid BP for the legato.

The Placid BP neg rail has failed it would seem. The symptoms are as follows:

With no load I get correct voltage (-13v) at output but no mV at all across R1.

With load the voltage at output drops to zero and still no mv across R1.

All the LED's light up ok. The heatsinks on the neg rail do not warm up in the slightest.

I have replaced the BC550C just in case and checked all the solder connections and re flowed a few. I wondered if the op amp or the QN1/QN2 transistors are ok. Could some one tell me what readings to expect on the outputs of these?

I'm puzzled as to what can go wrong after a year of use.