Hello everyone,
I have the following problem with my Hughes & Kettner Rotosphere effect:
- The overdrive section does not create distortion anymore
So far I have checked the following:
- Power supply is ok
- When I power up the unit, the "Saturation" LED is lit for approx. 10 seconds,
then gets dim. This is how it should be. The tube gets heated and its heater glows.
- The tube (12AX7A) is 100% ok.
In a different tube overdrive pedal, this tube works as expected.
I also installed a different 12AX7A tube in the Rotosphere, and this made no change.
- When I turn up the Drive pot, the output signal gets louder as expected.
After a certain level (pot 2/3 up), the yellow Saturation LED gets lit.
But the signal stays clean, the sound does not start to distort.
I have attached a schematic diagram of the unit.
Page 2: Input/Output with bypass and tube preamp
The overdrive section runs through IC 3 --> tube --> IC3
Page 4: Effect section
Is it possible that the signal is not being distorted by the tube
but rather by clipping diodes in the effect section?
"Effect in" gets the signal from the tube
Diodes B1 and B2 might be responsible for the distortion.
It seems that they are not in the signal chain anymore (don't know why)
The MN3207 ICs with clock generator 3102 (typical Chorus IC's) are responsible for the leslie-sound.
From here on everything works fine. Output is located on the lower right side.
I just can't find the reason why the distortion circuit is not working anymore.
Anyone got an idea?
Thanks for responses!
weiss
I have the following problem with my Hughes & Kettner Rotosphere effect:
- The overdrive section does not create distortion anymore
So far I have checked the following:
- Power supply is ok
- When I power up the unit, the "Saturation" LED is lit for approx. 10 seconds,
then gets dim. This is how it should be. The tube gets heated and its heater glows.
- The tube (12AX7A) is 100% ok.
In a different tube overdrive pedal, this tube works as expected.
I also installed a different 12AX7A tube in the Rotosphere, and this made no change.
- When I turn up the Drive pot, the output signal gets louder as expected.
After a certain level (pot 2/3 up), the yellow Saturation LED gets lit.
But the signal stays clean, the sound does not start to distort.
I have attached a schematic diagram of the unit.
Page 2: Input/Output with bypass and tube preamp
The overdrive section runs through IC 3 --> tube --> IC3
Page 4: Effect section
Is it possible that the signal is not being distorted by the tube
but rather by clipping diodes in the effect section?
"Effect in" gets the signal from the tube
Diodes B1 and B2 might be responsible for the distortion.
It seems that they are not in the signal chain anymore (don't know why)
The MN3207 ICs with clock generator 3102 (typical Chorus IC's) are responsible for the leslie-sound.
From here on everything works fine. Output is located on the lower right side.
I just can't find the reason why the distortion circuit is not working anymore.
Anyone got an idea?
Thanks for responses!
weiss