KEL84 Please Help

[hooger]

Hello,
I am new to this world of self build Hi-Fi and have just built the KEL84. I have just come to turn it on and find that after a few seconds there is a very large ac voltage at the speaker teminals and the output transformers make a loud humming noise. The 8ohm 11w load resistors I am using get very hot. I am reluctant to leave it on for any length of time so have not as yet been able to measure the voltages in the table. I have obviously messed somthing up along the way. Any suggestions on where I should start?
Any help would be greatly appreciated.
Olie

[NickG]

how big is the ac output voltage?

it cound just be you have the feedback the wrong way round and its oscilating, or you could have a wireing problem.

Have you tried it without the valves in, and checked the HT voltage is as expected on the center tap of the transformer?

[hooger]

Thanks for your reply Nick,
The voltage has got up to about 12 Volts before I turned it off but it could go higher. I have observed that the speaker teminals and the return of the phono sockets appear to be electrically connected to the chassis. Is this correct?
I have not tried it without the valves. Where do I measure the HT voltage?

[hooger]

It's ok, I was being an Idiot. I had the connections to the binding posts the wrong way round. It appears to be ok now. I have yet to listen mind. Thanks for your help.
Olie

[NickG]

Ok, so all that was going on was the feedback had changed from negative to positive and the amp was oscillating.

[hooger]

Ahh right. I have another problem now. It works ok at low volumes, but if i turn it up over a certain point (considerably less than half way) I get a buzzing noise out of the left channel and the amp start humming. I have tried swapping the valves over from left to right and that has no effect. Have I blown somthing up by wiring the wrong way round?
Olie