Technik und Service
Seite: 37
Technology and Service
Page: 37
mecablitz 44 MZ-2 / 44 AF-3
ENGLISH
The reflector position is determined by evaluating the voltage generated by the voltage divider consisting of
R4012 and the resistors R209 to R214 (depending on the reflector position), which is connected to pin 44
(ZOOM-POS) of the µC IC401. Between the various reflector positions, there is a voltage of about 5 V at
pin 44 of IC401.
When the desired reflector position is reached, the zoom motor is braked with a stop pulse generated by
momentarily switching pin 76 to HIGH and pin 75 to LOW: Tr201, Tr202 and Tr205 cut off; Tr203, Tr204
and Tr206 conduct and a reverse braking current flows through the zoom motor. The zoom motor stops at the
desired position and pins 75 and 76 return to HIGH.
In order to move the reflector towards the 28 mm position, pin 75 (MZ circuit board, ST201, contact 3,
ZOOML) switches to LOW, while pin 76 remains HIGH (MZ circuit board, ST201, contact 4, ZOOMH).
Transistors Tr203, Tr204 and Tr206 conduct while Tr201, Tr202 and Tr205 remain cut off. A current flows
through Tr204, the zoom motor and Tr203 and the reflector moves forwards.
In the 28 mm position, switch S202 is in position 1. When the desired reflector position is reached, the zoom
motor is braked with a stop pulse generated by momentarily switching pin 75 to HIGH and pin 76 to LOW:
Tr203, Tr204 and Tr206 cut off; Tr201, Tr202 and Tr205 conduct and a reverse braking current flows
through the zoom motor. The zoom motor stops at the desired position and pins 75 and 76 return to HIGH.
Flash readiness indicator:
With the aid of the voltage divider R4010/R4011, the voltage on the flash capacitor C001 is monitored at pin
45 (U MAIN CAP IN) of the µC IC401. If this voltage V
C001
is >280 V, the µC detects that the mecablitz is
ready for firing. Pin 66 (LED BB) of IC401 switches to LOW and the LED D408f or flash readiness indication
lights. A flash can now be triggered at any time by the camera or by pressing the button "Test" (S402).
Test flash:
If the button "TEST" (S402) is pressed when the mecablitz is ready for firing, a test flash is triggered. For this,
the µC IC401 switches pin 53 (IGBT-DRIVE) to HIGH. If the LC display is active, pin 60 (BACKLIGHT O/F
OUT) of the µC IC401 is switched to HIGH to switch off the illumination of the LC display.
Wake-up via user buttons:
In the menu of the mecablitz, the "Auto Off" function can be optionally activated to switch the flash unit
automatically to standby mode after three minutes. When this happens, the supply v5VG is switched
off (see 0). Instead of switching the mecablitz on again with the main power switch, it is possible to "wake it up"
with the aid of the user buttons.
The contacts of the buttons "Test" (S402), "Mode" (S403) and "Zoom" (S404) are connected via resistors to the
+5.0V supply voltage (which remains on in standby mode). If any of these buttons is pressed, the
corresponding pin (78, 79 or 80; interrupt inputs) of the µC IC401 is switched to LOW and the µC then
switches the mecablitz on again (wake-up).
The mecablitz can also be switched on from the standby mode by lightly touching the camera's shutter release
button.
