Service Manual

Bulb Exposure
An insulating material is set between the 2 sec. and B settings of the resistor VR-2
and this serves to distinguish between the normal shutter speed resistor and Bulb resistor.
The SW-4 serves as this insulating material.
When the shutter speed control dial is adjusted to "B" setting, the brush of the VR-2
comes into contact with the Bulb resistor.
The Bulb switch (SW-6) turns off when the shutter release button is depressed and turns
on when the pressure is released.
When the shutter speed control dial is adjusted to "B" setting and the shutter release
button is depressed, the bulb resistor and the brown lead wire are cut off from the plus
circuit (pink) and, therefore, no electric power is supplied to the condenser C1. Because
the voltage at both terminals of the C1 fails to rise, the normal switching of the transistors
does not take place, causing the magnet to hold the rear shutter all along.
When pressure on the shutter release button is released, the SW-6 is turned on. This sets
the flow of electric current through the Bulb resistor, starts the charging of the C1 and
initiates the switching of the transistors, causing the rear sector to be released from its
original position and thus closing the shutter.
The Bulb resistor does not wield any effect on the shutter function itself over the duration
the shutter release button is depressed. It is rather employed as a protection for the
transistor, owing to the fact that a huge flow of current is supplied to the base of the Tr5
when pressure on the shutter button is released and the SW-6 is turned on. Without this
resistor serving as a protection, the transistor is liable to be damaged due to the sudden
high flow of electric current.
ASA film speed setting
The brush mounting ring of the BALANCING resistor (VR-1) is designed in such
a manner as to enable ready rotation other than through manipulation of the main spindle.
In other words, ASA film speed setting actually consists of rotating the VR-1
differentially without affecting the function of the VR-2.