Audio Research Classic 60 & 120 owners

Hey Hifigeek1, thank you for your reply!
So from your experience, please advise how to adjust the bias port as it is located inside the cage!?

I suggest you find a qualified Audio Research Service provider.

Thanks, I will give ARC a call tomorrow.

Hello Pioneer48,
I used to own a pair of CL120 in the past, i i have done the biasing myself. The best solution is to remove the plate which is under the amp, and also the tubes cage. Then place the CL120 onto 2 pieces of wood (around 10cm * 10cm), then with that solution you are able to grip the measurement points to the multimeter (That is really preferable to grip the measurement points when the amplifier is not switch on, otherwise it can be extremely dangerous).
Then it is also important to let the amp connected to an old speaker or resistor of 4 or 8 Ohms. Then switch on the amp and follow the evolution of the voltage. Then when the voltage is quite stable (after 20-30 min), adjust the bias the 65mv DC. If during the stabilization phase the bias goes over 65mv, reduce the bias via the appropriated pot.
You can operate with no tube cage, just for the bias setting, but it is not recommended to run the amplifier, without the tube cage. When you change the measurement point, please switch off the amp, but please be extremely care, the capacitors are dangerous even when the amp is not switch on. If you want some pictures, i do still have some from my V35 amp, basically is the same operation, so please send me your email @
Laurent

At last, I managed to identify the cause of the Line fuse that keeps blowing on one of the amp.

Hifigeek1 guess was correct. It is due to a faulty tube! I do not know how many were faulty as I replace all six tubes with new ones.

These replaced tubes were less than 100 hours of use. It just shows new tubes can be faulty at times.

I do not have a tube tester. Can anyone suggest how I can find out which one is faulty from the six I have taken out?

Thanks