Hello,
I recently acquired a mono/poly that has oscillator 1 out of scale.
I've read the calibration procedure in the service many and I'm not
sure if I am understanding it correctly. Aside from that, I believe
my primary issue lies with the trimpots on KLM-398 (i.e. VR1, VR2,
etc.). Assuming that I, in one of the ways I have tried to tune the
synth, am following the procedure correctly, then this must be the
issue. A brief note that I should mention is that my KLM 354 board is
not labeled so I assume that I am tuning with the correct trimpots
(VR10X) but I could be wrong. I am fairly sure that this is not the
case though. I am copying my post from another forum from here.
After literally hours of trying to do this, I've come to the
conclusion that I can proceed no further without some sort of help/advice.
I have been following this procedure and have had NO luck scaling the
oscillator.
First I tune A#4(Highest A#) with VR 102 at 16' to be exact (0 cents off).
Then I tune A#1 (Lowest A#) with VR 103 at 16' to be -5~-10 cents off.
Then I tune A#1 with VR 101 at 2' to be exact (0 cents off).
Then I am left with tuning A#4 at 2' with VR104 which simply does not
work, because, at this point, it is impossible to tune to A# at the
extreme of the trimpot.
While writing this I thought I may have reversed the tunings for VR
104 and VR 101 so I switched the which trimpot I tuned with and it
allowed me to tune all of the keys to A# as desired.
However, the keyboard is still badly out of scale. The first F is very
(+20 cents) sharp and it sort of flat on almost every note until a
certain note at which it goes sharp again.
I believe this problem to be with the trimpot VR1 and to be an effect
of the offset voltage not being +-0.1mV. However, I'm not at all sure
how to check this. I went to radioshack and bought a digital
multimeter which was a bad idea in that its lowest readable value is
0.1mv. Even so, I don't know where or how to verify whether the offset
voltage for the VCOs is 0.1mv (or even close).
Even if someone could please confirm that I am following the correct
tuning procedure I would be very grateful.
I also need to know how to "test the lead wire from KLM 398" to test
the offest voltage, but I will take any and all advice.
Thanks in advance.