How to Set Bias for Left Power Tube of Amplifier

Video Transcript

"Hello. This is Jeff Naylor from Mtroniks Engineering in Mesa, Arizona for Expert Village. Now that the tubes are warmed up, we're going to bias them using the current method. Connected to the cathode of the tube to ground, there's a one resister. If we measure across this resister, we get a voltage. This voltage correlates directly into the current of the amp when it's on standby. The standby current specification for this amp tells us we should have eighty millivolts. Right now we're reading thirty-one point one millivolts. We want to adjust this mini pot in here until we read eighty millivolts on the voltmeter. In this DSL 60, we have one bias adjustment, hot. However, in other versions of the JCM 2000 series, such as the TSL 100, we'll have two adjustment pots; one on this side and one on this side. As I turn the pot clockwise, the voltage increases. I want to slowly approach eighty millivolts and then allow for the amp to settle. That's pretty close. Now that we've got the left tube properly biased, we can go on to the right tube. See you in the next section."