And here's the voltage for all "C" keys, starting from the lowest C and 16'
to the highest and 4'. Measured on the new production board, after the
demultiplexer. Stretch tuning is off (this is important!). Multimeter
ground is TP4 (-10V).
0.018
0.042
0.090
0.185
0.375
0.755
1.513
3.03x
The doubling of the voltage for each octave is easy to see. I think this
antilog amp has a good calibration; perhaps at the bottom there is a little
bit of room for improvement.
So we have essentially a doubling for every 0.5V at the input.
With VR1 to VR3 we can change the relation of those voltages for certain areas.
The service manual says:
VR1 ADJ. CENTER
VR2 TUNE HIGH
VR3 TUNE LOW
VR15 TUNE MID
However I'm not a 100% convinced that the functionality of VR15 and VR1
isn't switched.
VR15 seems to control a general offset while the other VR's indeed control
their respective ranges. They're affecting the tuning a bit outside their
range but not much.
A comparison of the old and new production also hints at this:
VR1 MID
VR3 LO
There seems to be no VR2 for the old production.
And the addendum says
"VR15 on KLM-366 is equal to VR1 on KLM-396."
The latter is the daughterboard for the old production; hence VR15 is NOT
the same as VR1 (which is simply labelled "MID") on the old production
KLM-366.
So my guess is that the four VR's for the new production should better be
labelled:
VR1 TUNE MID
VR2 TUNE HIGH
VR3 TUNE LOW
VR15 ADJ. CENTER
to the highest and 4'. Measured on the new production board, after the
demultiplexer. Stretch tuning is off (this is important!). Multimeter
ground is TP4 (-10V).
0.018
0.042
0.090
0.185
0.375
0.755
1.513
3.03x
The doubling of the voltage for each octave is easy to see. I think this
antilog amp has a good calibration; perhaps at the bottom there is a little
bit of room for improvement.
So we have essentially a doubling for every 0.5V at the input.
With VR1 to VR3 we can change the relation of those voltages for certain areas.
The service manual says:
VR1 ADJ. CENTER
VR2 TUNE HIGH
VR3 TUNE LOW
VR15 TUNE MID
However I'm not a 100% convinced that the functionality of VR15 and VR1
isn't switched.
VR15 seems to control a general offset while the other VR's indeed control
their respective ranges. They're affecting the tuning a bit outside their
range but not much.
A comparison of the old and new production also hints at this:
VR1 MID
VR3 LO
There seems to be no VR2 for the old production.
And the addendum says
"VR15 on KLM-366 is equal to VR1 on KLM-396."
The latter is the daughterboard for the old production; hence VR15 is NOT
the same as VR1 (which is simply labelled "MID") on the old production
KLM-366.
So my guess is that the four VR's for the new production should better be
labelled:
VR1 TUNE MID
VR2 TUNE HIGH
VR3 TUNE LOW
VR15 ADJ. CENTER