Hello All,
my 2nd-hand 440 became sick the other day and I'm afraid I need help to get it fixed:
The obvious thing: it does not self-oscillate.
With no input (either INx is 0 or open INs), setting FREQ to about 7 and setting RES up to 6 and
above just gives a slow rhythmic "plop" as if I fed
an slow asymmetric pulse into a LP.
It goes faster the higher the RES value goes.
at around 4-5 on the input level pots (all INs are affected) the Signal starts to mix with the "plops".
The scope shows two decaying shapes as if a cap discharges. One goes positive the other negative.
It does filter an incoming signal with low RES settings.
Setting higher RES values changes the sound (e.g. when sweeping FREQ) but it always sounds very tame.
RES settings from 6 on starts to distort the sound when sweeping FREQ.
I did a small clip to show what can be seen on the oscilloscope:
http://www.youtube.com/watch?v=OnFvf7z_i2M First there's the no-input situation as described above.
Then it shows sweeping the RES from 0 to 10 and back and again to 10.
Leaving RES on 10 (where it should scream) FREQ is swept to 0 and to 10 again.
This audible glitch occurs at around FREQ 9 when turning counter-clockwise.
The input level pots are set to 7 (shortly before the scope shows slight clipping).
I also checked the RES input: the VCA for the resonance appears to be ok,
the overall behavior is the same.
I'm having a hard time identifying the problem.
I hope I could make clear what the situation looks like.
Any hints are appreciated!
Many thanks, Michael.
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