Reset Circuit; Usb Connector Interface; Switch Pedal Connector And Interface; Scanport Interface To Volume Control Potentiometer - Kurzweil CUP2 Service Manual

Reset Circuit

(page 2, zone A3)
Reset for the main CPU on the Engine PCB is controlled by the Audio PCB via this circuit on
the Interface PCB. The power supply on the Audio PCB creates a signal called PWR OK, which
is pulled to +15V when DC voltages are in tolerance. Resistors R58 and R59 reduce the PWR
OK signal swing to 4.5V. When PWR OK is high, C56 is allowed to slowly charge by a 20K
pullup resistor on the Engine PCB. The CPU on the Engine PCB begins running when the
voltage on C56 reaches about +3V.
When power is switched off, PWR OK will go low well before the DC power voltages begin to
decay. This forcefully discharges C56 through D3 thus halting the CPU and activating the
muting circuits before glitches due to failing power can be generated.
DC power is transferred from the Audio PCB to the Engine PCB through J15 and J25. L4 greatly
reduces audio interference from noise created by the Engine PCB on the VCC power bus.

USB connector interface

(page 1, zone A1)
The USB jack connects directly to the USB Control and Data cables that connect to the Engine
PCB. Note that the Data cable must be constructed from special USB rated shielded cable for
reliable operation in high-speed mode.

Switch Pedal connector and interface

(page 1, zone A5)
J3 is a triple switch pedal input. The switch pedals close when pressed. Thus the voltage at
LPDL, CPDL, and RPDL will be +5V when the corresponding pedal is up and near 0V when
pressed. These signals then enter the Analog Multiplexor (described on the following page).

ScanPort interface to Volume Control potentiometer

(page 1, zone C3)
Volume in the CUP2 is actually controlled by digital commands from the Engine PCB CPU to
the synthesizer ASIC. The volume control potentiometer is interfaced to the CPU (along with
the pedal signals) through the ScanPort as an analog signal.
The volume control potentiometer is installed on the Control Panel PCB located in the Control
Assembly. These three signals then go to the Interface PCB through the Control Panel cable and
appear at Pins 1
In operation, the top of the volume control potentiometer has a DC voltage of +5.0V applied.
The bottom is grounded and the wiper thus acquires a DC voltage proportional to the volume
setting. This voltage then goes to the analog multiplexor (description follows).
3 of J7 on page 1, zone C3.
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Printed Circuit Boards
Interface PCB
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