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previous: Rob W. Hello Everybody!I h... -- 12/13/1999 1:29 AM View Thread

Re: Frustrated Tech Moment... :-(

12/13/1999 9:49 PM
Scott Swartz
Re: Frustrated Tech Moment... :-(
I have not seen the schematic for this amp, so what do you mean by this:  
"Crate has some sort of wierd biasing circuit that runs off of its own winding on the power tranny"
Is it a bias tap for a half wave rectifier ala Fender and others, or does it have two wires going to a bridge or full wave rectifier?  
What AC voltage is available going in to the rectifier?  
Have you checked the bias components (cap, diodes)? What is the bias voltage available before the divider? What bias voltage are the tubes seeing?  
Is there a bias pot? If not, you can change the divider resistors to get the right voltage.  
It appears you got your current measurement by inserting the meter between the OPT CT and the B+. Its possible you have one bad tube and the others are actually biasing up properly. The 1 ohm resistor at the cathode trick will tell you the current draw of each tube.  
More info would be helpful in troubleshooting this issue.  

Rob W. Re: A picture of the problem: -- 12/14/1999 12:09 AM