Right Channel Noise in KT88

Dear friends,

My friend got a KT88 power amp that gives off "ssss....sss" noise on the right channel. The funny thing is, the noise is random. Sometimes you hear it when you start it up, sometimes it appears when the machine is turned on for 1 hour or more.

What could have caused the problem? Swapped the tubes already, still no good.

AND the right channel OUTPUT transformer is really HOT compared with the LEFT one.

CAT

Dear Accphoto,

My colleague used different tubes already (e.g. swap left right) and the problem is still consistent in the Right Channel. So probably it is not the tube.

I know how to measure BIAS for my 6L6 as there is a hole in the chasis. For this CARY KT-88, I have no idea how it can be done.

Should I post some photos here so that you can give me more advice?

Thanks in advance.

CAT

Dear Accphoto,

Additional information. The KT-88 is a CARY SLA-70 Signature Model. My friend said it is AUTO Biasing.

CAT

Dear Accphoto,

I managed to shoot some photos with the KT88 before I dis-assembled it. Hope this can help.

The owner took the Amp to Apliu Street for repair but was unable to cure the problem.

CAT

Dear Accphoto,

Is it because of the potentiometer you see in the photo?

I am re-building the whole thing. After that, I will consult you on what to measure at which point.

Thanks  

CAT

Dear Accphoto,

You are indeed an expert to these stuffs. Yes, you are right, there is ONE 6.8Ohm for both KT 88.

I am now re-painting the chasis. After that, I will put everything back together.

Please teach me HOW to adjust the BIAS and tune this thing back to normal. Thanks in advance.

CAT