bias Classic 60, Audio Research

ARC will fax you the info.
If you do it your self you should get probes that will clamp onto the resistor.
Then you can do one channel at time with the amp on it's side then turning onto the other side for the other channel.
Get a set of probes that have a few inches of reach and are well insulated.

nice amp

LM

I'll bet you the pink slip you don't have a meter so the best advice I can give is take it to a local shop.Which is not to say the first poster can't walk you through it,which is a nice move on his part.Good luck,were all in this together,Bob

Hi George,
It simple to do, i did several times when i had this amplifier. First of all you need matched tubes (Matched Octet tubes).
Switch Off the amplifier and unplug the 110V
Then remove the tubes cage and place the trimer in Med position
Then place the amplifier to be lying on one side
Remove the top back cover to access to the circuit board
100 Ohms resistor are located near the Power and output transformer, they are 2 W and are in black color (you should be able to find pins near this resistor for TP1, TP2, TP3 and TP4
So use Alligator clip between 2 resistors and place the DVM on Continuous Voltage, for measuring at least 200mV
Then Plug the 110V and Switch on the Amp
The DVM should start to display voltage for 10 - 20 mV at the beginning and increase at least for 30min then it should be stable (during this phase if the 65-70 mv is reached turn a the trimer a little bit to read lower than 65mv
So when it is stable, adjust the value to 65mv
Verify the other resistor they should between 5mv in general if your tubes are matched
If you provide me a email address, i should be able to send you some pictures, i did some when i used to run the procedure
I hope this helps
Laurent

could send picture to email ngockhanhpl@yahoo.com

I will throw my 2 cents in. You need long hook clip probes to safely measure the bias. There is an issue biasing this amp because it uses an opto-coupler and an IC to servo its mating output tube. Once you adjust the biasable output tube the slave tube is supposed to meet it. The problem is it takes forever for the servo to work. On each side of the amp is a small access hole to adjust the slave tube bias. A very small adjustment can make a large difference and again you have to wait for the adjustment to work. It takes me over an hour to properly set up a CL-30/60/120. I would suggest letting a competent service provider do that for you. I have seen many instances where the servo does not function properly and when these amps are purchased used there's always a chance. If the servo malfunctions it's possible for the tube to run away.