Kodak 9020/CINE service manual Lamp Voltage Zero-Cross Signal

Service Manual

a) Lamp Voltage

b) Zero-Cross Signal

c) Internal Counter Clock Signal
4096 Pulses	4096 Pulses

d) Example

1000 0 1000 0

e) Trigger Impuls

d) Actual Lamp Voltage

SM 2547-1

The zero-cross circuit creates an impulse whenever the LAMP voltage crosses the zero line (LAMP voltage close to zero). See figure b.

Therefore, every 10ms for 50Hz or 8,3ms for 60Hz a signal change occurs. This signal is sent to the DISSOLVE LOGIC on the MASTER PCB. The DISSOLVE LOGIC generates a clocksignal with 4096 pulses for the length of half a sine wave. This clock signal is triggered by the zero-cross signal.

See figure c.

Through the DATA SIGNAL, the MICROCONTROLLER delivers a value between 3 and 3700 to the DISSOLVE LOGIC. Values of 0 to 4096 are possible, but these valves would cause

false phase cut positions because the zero-cross signal does not detect zero on the sine wave.

At the next zero-cross of the LAMP voltage, the DISSOLVE LOGIC reads the value in the MICROCONTROLLER. This value can range from 0 to 1000, and is counted by internally generated clock signal. The clock signal sends the TRIAC TRIGGER signal to the TRIAC CONTROL on the POWER CONTROL PCB.

The TRIAC is energized and the LAMP is energized for the rest of that half sine wave.

If the MICROCONTROLLER sends a new value, the next half would have a different phase cut position. If the value is not changed, the cut position leaves unchanged.

The LAMP dissolve function operates between zero and high with an accessory in the accessory slot or with RS232. High or low on the LAMP is controlled by the BRIGHTNESS SWITCH.

The dissolve range of zero to full brightness is divided into 1000 steps. These steps can be used to create a linear LAMP brightness change.

A lookup table is used in the MICROCONTROLLER software. This table contains the corresponding phase cut value for each one of the 1000 steps for a linear brightness setting.

figure 3-11

03/98 3-14 Kodak AG, Stuttgart