Technik und Service
Seite: 47
Technology and Service
Page: 47
mecablitz 44 MZ-2 / 44 AF-3
ENGLISH
Wake-up by the camera:
After the flashgun has been switched off automatically (Auto-Off), the mecablitz can also be switched on again
by slightly depressing the camera shutter release.
The collector of Tr411 in the input circuit of SK2 (CLOCK) is connected via R4039 to the +5.0V supply voltage
(which remains on in standby mode). The first time the user slightly depresses the camera shutter release, the
camera sends a HIGH pulse via SK2 to the mecablitz. After inversion with Tr411, this generates a LOW signal
of the same length at Pin 51 of IC401 (CLK/TTL) which triggers an interrupt and the µC IC401 then switches
the mecablitz on again.
9. Nikon Functions (mecablitz 44 AF-3N):
With Nikon cameras listed under Group A (bus cameras) in the Operating Instructions for the mecablitz, a
digital data transfer (e.g. ISO value, focal length, aperture, flash readiness, reflector position, etc.) takes place
between the mecablitz and the camera. A common clock line (SK1 ) and a common data line (SK2) are used
for the digital data transfer. With Nikon cameras listed under Group B (non-bus cameras) in the Operating
Instructions for the mecablitz, there is no digital data transfer between the mecablitz and the camera. There is
no maximum flash-range indication on the LC display of the mecablitz when a Group B camera is connected.
Camera interface:
On the mecablitz 44AF-3N, the interface to the camera consists of five contacts:
SYN contact, special contacts SK1 to SK3 and two ground contacts on the sides
(connected in parallel).
(Contacts viewed from below)
Special contact SK1 with non-bus cameras
Synch speed switching:
When the mecablitz is mounted on the camera, a resistor of about 18 kOhms within the camera is connected
to SK1 and the resulting voltage on SK1 is about 1.2 V. The camera detects from this voltage that the flash unit
is switched on and switches to its synch speed. The mecablitz does not need to be ready for firing.
Flash readiness indication in the camera's viewfinder:
When the mecablitz is ready for firing, the µC IC401 switches pin 65 to HIGH. This signal drives the base of
Tr410 via R4033 and Tr410 conducts. An additional current is now fed into the camera via R4032 and Tr409.
Due to this current via Tr409, the voltage on special contact SK1 rises to about 2.6 V and the flash readiness
indicator in the camera's viewfinder lights.
Correct exposure confirmation in the camera's viewfinder:
If, in TTL flash mode, the flash was not sufficient for correct exposure of the subject, an optical warning signal
in the camera's viewfinder lights to indicate this: the flash readiness symbol in the viewfinder blinks for about
three seconds. In order to cause this blinking, contact SK1 transmits a square-wave signal. The µC IC401
generates this signal by switching pin 65 periodically between HIGH and LOW, causing Tr410 to alternately
conduct and cut off. The voltage on SK1 thus alternates between 2.6 V and 1.2 V. The camera remains set to
its synch speed.
