I have a Denon 1906 connected to two Mission M34i floor-standers and a Boston Acoustics 150W powered sub-woofer. Some time ago, the amp had stopped powering on. When turned on, it would "boot", if you know what I mean, for about 2-3 seconds and then instantly turn off. I gave it to a repair center and got it fixed. The diagnosis was that some transistors had failed and were replaced. After getting the amp back, I can now successfully turn it on without issues. However, I am no longer getting proper volume levels out of the amp. I thought this might be because earlier the amp was powering four M34i speakers and had the individual channels set to suit my taste. So, I went into the channel setup in order to change the channel levels to determine if that was the problem. The moment the test tone started, however, the amp turned off again! This happened repeatedly when tried on 2-3 occasions. I am worried about frying some components again so I want to know what the problem might be. When all four speakers were connected, I used to get really good volume levels at about -15 to -20db but with just two speakers, even below -15db the volume is very low. Any help in figuring out if the problem lies with the amp, cables or speakers will be greatly appreciated.