Thanks EchoWars:...but I don't think I like the tone of your response! I appologise if something in my question has reminded you of the iognorant great unwashed who read this site and attempt to learn through it! It could just be me, as I am a bit over sensitive these days trying to learn this stuff and seemingly recieving less than helpful insights from pointeers such as your response. There's lots of people with knowledge, but us lesser mortals have to bow and scrape a lot to get access to it. And it seems that 'moderators' these days are on the side of the well established guys, and not us learners. I have recieved my fare share of unhelpful comments from other sites and was hoping this to be different. Admittedly, that was referring to speakers, which seem to hold their fare share of mystery! But it seems to me that this site may as well be like the others. PLeae honour me with your esteemed opinions again! I am sorry to be a pain, and obviously ignorant!
Now, in my AU999 it has a group of 4 larger 'flying Saucer type transistors' that screw into the heat sink and have eclectrodes that poke through, with a grommet into the circuit boards mounted on the other side. Mine had 2 X NTE 28089IF in the front (one on the right anbd one on the left) and 2 X Hitachi 2SC898 on the back 2Sc898....one on the right and one on the left. On the floor inside the amp, it had 2X 2AS 586 in the front (one on the right and one on the left) and behind at the back it has 2 X 2SC680 similarly one on the right and one on the left. These smaller ones I though to be the pre-amp transistors and the larger the ones for the power amp modules.
Now as for your supportive advice. Well mate, I asked the question. I got little return, except for the really helpful attitude!. Some loverly person suggested that the larger flying saucer type should all be the same : the original Hitachi 2SC898. I had a mixed bunch as I stated above. He suggested replacing them all with Sanken 2SC1116A or Sanken 2SC2607. I bought the first option. In fitting these I may have neglected to replace the grommets which would mean it would arch, short out and not play. This is what seems to be happening. Anyway, the other Sanken are on their way to me the SC2607, as are replacement gromets. I shall then take the poor old amp to a techitian.
So, you are suggesting I do what???????
Don't worry, I shall not be back.