Scanport Interface To Control Panel Buttons; Scanport Interface To The Keyboard; Midi In/Out Connector Interface; Ac Power Input Jack And Voltage Selector - Kurzweil CUP2 Service Manual

Printed Circuit Boards

Interface PCB

ScanPort interface to control panel buttons

(page 1, zone C4)

The buttons are in a 6 column 2 row interface. The columns are shared with the LEDS. The

status of the rows is driven back to the ScanPort by buffer U4. A pressed button will send back

a zero for its row position when its column select line is low. Buttons that may be pressed

simultaneously are never on the same row. The button switches are on the Control Panel PCB.

(page 1, zone 1B––1D)

The keyboard connects to J4 (Treble) and J5 (Bass). Bass is a 10 column by 8 row matrix (40

keys, 80 switches) and Treble is a 12 column by 8 row matrix (48 keys, 96 switches). These are

combined into a 22 column by 8 row matrix for 88 keys total.

Shift registers U12, U11, and U10 drive the columns low one at a time. Buffer U13 transmits the

state of the rows back to the ScanPort. Each time a row is read, the column shift registers

advance one column. A new scan begins when the ScanPort RES signal is low during a

keyboard row read cycle. Scan rate is approximately 4KHz (250uS).

(page 2, zone D5)

U14 is the MIDI In current loop receiver. A 6N138 is used. To be compatible with the CPU on

the Engine PCB, voltage divider R22 and R62 limit the MIDI signal voltage swing to 3.3V. U15

drives the MIDI Out and MIDI Thru connectors current loops.

(page 2, zones D1––D3)

J22 receives line voltage AC (either 115V or 230V). AC power then is routed through the remote

power switch through J23 and through fuses F1 and F2. When the switch is turned off, R52 and

C33 protect the power switch contacts from arcing caused by the large power transformer. C34,

C35, common-mode choke L3, and C36 together form an RFI lter to reduce conducted

emissions.

J24 combined with the power transformer primary plug form the line voltage selection

method. When the plug is placed on pins 1-4, the two primary windings will be connected in

parallel for use with 100-125V AC power. When the plug is placed on pins 4-7, the windings

are connected in series for use with 200-250V AC power.

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