9720 VCO 17
010321
one in the middle and the other two halfway to either end. Cinch
the ties tight and clip off the excess.
( ) Locate the power connector header and install it in the
appropriate location on the FracRak format power
supply you will be using. Note the orientation of the
locking tab shown in the illustration. Push the 4 pins
through the board but solder one pin only. Examine the
header to see that it is seated flush on the board and if not,
remelt the single joint and push the connector fully into place.
When satisfied, solder the remaining three pins.
( ) Turn the control shafts of all the potentiometers fully counter
clockwise and mount each knob in turn by placing it on the
shaft and aligning the pointer with CCW end of the panel
graphic. Tighten the set screw slightly and rotate the control
back and forth to see that its range of rotation is centered
with respect to the panel graphic. Loosen the screw and
realign the knob as needed and fully tighten when done.
The moment of truth is at hand, the next step will be to power up the module and start testing.
This is an excellent time to take another break, stretch and think about something else for a
while. When you come back take the time to do a final check. The flying wires to the panel
aren't bundled with wire ties yet, and we'll leave them that way for now, so move them around a
little to check the connections. Inspect the wiring on the panel and make sure none of the bare
wire used as the panel ground is in danger of shorting against other connections. One more
pass of inspecting the board for component polarity and quality of solder joints is a good idea
too.
TESTING
Set Scale A and B trimmers (R27,R58) to the midpoint
of their rotation, corresponding to a 1V/oct scale.
Also
set Sym A and B (R87,R5) trimmers midscale. Make
sure the power supply is turned off and mate the
power connectors.
1) Set the 9720 knobs and switch as shown and turn on
power. First observe the POWER light on the power
supply and if it doesn't come on stop and find out why.
It may be just a dead outlet or some more serious
problem such as a solder bridge on the 9720 board.
If the power supply light comes on when the 9720 is
disconnected, it's a sure sign of a problem on the 9720
board. The most likely area for this problem is in the
area around the power connector, R1, R2, C1, C2 and
the voltage regulators IC1 and IC2.
2) Check the modulator light on the 9720 front panel. It
locking tab
FracRak format
power supply
(9770, midi2cv8, etc.)
Summary of Contents for 9720
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