I've been working for a while trying to find the issue with an ampeg v4-b amplifier a customer of mine brought in for repair.
Now bear with me, this is kind of a wordy and involved question.
This amplifier has a constant pink noise type sound with crackling and the signal is very weak and distorted.
I signal traced the bad sound to the pin 2 of the 6k11 (the output of the first gain stage the 6k11 produces).
With the tube removed pins 2, 5, and 10 (where b+ is being fed to the different sections of the tube) show high voltages that coincide with the original ampeg schematic. However when I reinstall the tube pins 2 and 5 (which are fed by resistors) drop dramatically to about 40 volts on pin 2, and 8 volts on pin 5. Pin 10 remains high.
I tried replacing the 220k and 470k resistors that feed b+ to pins 2 and 5 respectivly, but the same problem. I ordered a 6k11 (philco) tube from CE distributions and had the same problem when installing this tube. Is this an issue of 2 shorted tubes? Is there something else I should be checking for?
Here is the schematic for anyone to look at.
http://www.schematicheaven.com/ampegamps/v4bpreamp.pdf
If anyone has any insight as to what might be going on that would be great!
Now bear with me, this is kind of a wordy and involved question.
This amplifier has a constant pink noise type sound with crackling and the signal is very weak and distorted.
I signal traced the bad sound to the pin 2 of the 6k11 (the output of the first gain stage the 6k11 produces).
With the tube removed pins 2, 5, and 10 (where b+ is being fed to the different sections of the tube) show high voltages that coincide with the original ampeg schematic. However when I reinstall the tube pins 2 and 5 (which are fed by resistors) drop dramatically to about 40 volts on pin 2, and 8 volts on pin 5. Pin 10 remains high.
I tried replacing the 220k and 470k resistors that feed b+ to pins 2 and 5 respectivly, but the same problem. I ordered a 6k11 (philco) tube from CE distributions and had the same problem when installing this tube. Is this an issue of 2 shorted tubes? Is there something else I should be checking for?
Here is the schematic for anyone to look at.
http://www.schematicheaven.com/ampegamps/v4bpreamp.pdf
If anyone has any insight as to what might be going on that would be great!
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