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I'm having a problem with distortion on a Blues Junior. It happens at pretty much all volumes, low and high. It's not very severe, just noticeable when I play two notes or more. I do have another Blues Junior to compare it to also.
I have tried changing all the tubes. I have tried connecting a different speaker.
I changed the bias resistor (R52 in the power supply section) 22K to a higher resistance. I'm using a variable resistor and now it's closer to 27K. This is changing the C- voltage to about -12vdc (instead of stock -10.6vdc) and also lowering the current draw of the power tubes to about 25mA. I got info on this from Billm website.
The bias change doesn't seem to affect the distortion problem. It still happens if I run the tubes hot or cold.
I have tested the voltages at indicated points on the schematic such as B+, Z, Y, X and the cathodes in the pre-amp section. Everything seems pretty close to the schematic voltages. The B+ goes up by about 20v when I lower the bias.
I have attached a schematic.
Any ideas on what I should do next?
Thanks.
I have tried changing all the tubes. I have tried connecting a different speaker.
I changed the bias resistor (R52 in the power supply section) 22K to a higher resistance. I'm using a variable resistor and now it's closer to 27K. This is changing the C- voltage to about -12vdc (instead of stock -10.6vdc) and also lowering the current draw of the power tubes to about 25mA. I got info on this from Billm website.
The bias change doesn't seem to affect the distortion problem. It still happens if I run the tubes hot or cold.
I have tested the voltages at indicated points on the schematic such as B+, Z, Y, X and the cathodes in the pre-amp section. Everything seems pretty close to the schematic voltages. The B+ goes up by about 20v when I lower the bias.
I have attached a schematic.
Any ideas on what I should do next?
Thanks.
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