Service Manual

4.3.3 Shutter closes automatically at "B" setting.
Specifically, this malfunction consists of the shutter closing automatically at "B" setting
while the shutter release button is being depressed or of the shutter functioning at speeds
faster than the normal at slow speeds (ranging from 1/8 to 1 sec.).
This is caused by improper insulation between the plus (pink) circuit and the "Bulb"
resistor incorporated in the shutter speed resistor (VR-2) as well as the brown lead wire
circuit.
4.3.3.1 Poor insulation of the shutter speed resistor.
After adjusting the shutter speed control dial to 1/1000 sec. setting, check the insulating
resistance of both terminals of the "Bulb" switch (SW-6) with the aid of an insulating
resistance meter. The reading in this case should be 100 megohms or more.
The points where poor insulation may be caused most commonly are:
1. Soldered sections of the lead wires of the "Bulb" switch (SW-6) or improper
adjustment of the position of the contact pieces.
2. Soldered sections of the lead wires of the shutter speed resistor (VR-2).
3. Poor insulation of the "Bulb" resistor.
In case of (b) and (c) above, wipe and clean the pertinent parts carefully with lacquer
thinner.