Question: how to bias jcm 900?
Answer: Remove the Amp from its housing. [00:08], Tilt the head up and remove the electronics. [00:22], Set the electronics flat. [00:41], Remove the spring caps on the power tubes. [01:00], Grab from the base and pull straight up. [01:39], Repeat for all the preamp tube sockets. [02:48], The balanced preamp tube goes in V3, nearest the power tubes. [04:12], Replace the preamp tube covers. [04:40]