I'm trying to stop my hohner orgaphon from oscillating.
I first noticed that the overdriven sound was harsh, gritty.
This is what it looks like hooked up on a scope.
at -20dB input
and at -15dB input
I did not find a schematic, for the model I have (I highly suspect it to be a 41MH),
this should be close though.
I believe the signal is good up to the powertubes (2xpl84)
When I measure after the 22nF (blocking cap after the PI) the signal there goes to a sort of blockwave, without the spikes.
I tried replacing tubes, same oscillation.
I tried caps over the output transformer, not much difference.
My voltage for the PL84 are :
anode 356V
screen 200V
bias -22V
heaters are 14,65 for the pl84, 6,5 for the ecc83.
If anyone has an idea what I can try next ....
I first noticed that the overdriven sound was harsh, gritty.
This is what it looks like hooked up on a scope.
at -20dB input
and at -15dB input
I did not find a schematic, for the model I have (I highly suspect it to be a 41MH),
this should be close though.
I believe the signal is good up to the powertubes (2xpl84)
When I measure after the 22nF (blocking cap after the PI) the signal there goes to a sort of blockwave, without the spikes.
I tried replacing tubes, same oscillation.
I tried caps over the output transformer, not much difference.
My voltage for the PL84 are :
anode 356V
screen 200V
bias -22V
heaters are 14,65 for the pl84, 6,5 for the ecc83.
If anyone has an idea what I can try next ....
