I recently completed an 8-step version of the sequencer/programmer.
There were three problems with it when I first tested it, two of which
I located - a solder whisker joining two of the board buses and a dry
joint on a resistor. The third one is stumping me.
Row 2 of the sequencer, when the pots are at zero, and the CV out is
connected to a VCO CV in, the VCO puts out the same pitch as the other
three rows do when they're at zero. However, when you rotate the pot
clockwise, the pitch goes down instead of up! On row 1,3 and 4 the
pitch goes up as expected. Having examined the schemo, I figure the
problem must be located with some build error either on row S, or on
the tl072 that is at the output of row 2, however having carefully
examined the boards, I can't find what I've done wrong! Any
suggestions? I tried replacing the 072, and resoldered the 2 smd caps
on the back of it, no effect.
I'm very pleased with this piece otherwise, it's great, many thanks Ken.
There were three problems with it when I first tested it, two of which
I located - a solder whisker joining two of the board buses and a dry
joint on a resistor. The third one is stumping me.
Row 2 of the sequencer, when the pots are at zero, and the CV out is
connected to a VCO CV in, the VCO puts out the same pitch as the other
three rows do when they're at zero. However, when you rotate the pot
clockwise, the pitch goes down instead of up! On row 1,3 and 4 the
pitch goes up as expected. Having examined the schemo, I figure the
problem must be located with some build error either on row S, or on
the tl072 that is at the output of row 2, however having carefully
examined the boards, I can't find what I've done wrong! Any
suggestions? I tried replacing the 072, and resoldered the 2 smd caps
on the back of it, no effect.
I'm very pleased with this piece otherwise, it's great, many thanks Ken.