Service Manual

4.2.2.1 Burn-out of the "OVER" indicator lamp ("UNDER" indicator
lamp).
Remove one of the terminals of the "OVER" (or "UNDER") indicator lamp and
undertake continuity test. If no continuity is determined, make replacement of the lamp.
4.2.2.2 Malfunction of the amplifier unit.
If the indicator lamps are found to be in order, it is an indication of a malfunction of the
transistors of the amplifier unit, necessitating replacement of the unit.
4.2.3 "OVER" indicator lamp turns on continuously and "UNDER" lamp
fails to turn on.
This malfunction can be attributed to excessive rise in the electric potential of (T5)-(T1)
due to either shortcircuiting of the CdS or failure of the BALANCING resistor (VR-1) to
provide normal function. Normally, the voltage at (T5)-(T1) should be within the range
of 0.6V and 1.0V at the point where both lamps turn off.
4.2.3.1 Shortcircuiting of the CdS.
Because shortcircuiting of the CdS itself is quite improbable, check whether or not the
CdS baseplate is shortcircuited.
Remove the blue lead wire of the amplifier unit on the CdS baseplate, apply the tester
rods between the colored patterns and undertake continuity test.
When the lens aperture is set manually to f/5.6 and a light emitted by a standard light
source is directed, each CdS should give the following resistance value (The reading
should be approximately half this figure in case measurement is taken of both CdS cells
simultaneously):
BLV 7 60 - 160K ohm
BLV 11 10 - 20K ohm
BLV 15 1.35 - 3.5K ohm
4.2.3.2 Failure of the BALANCING resistor (VR-1) to provide normal resistance
function
Remove the blue lead wire of the VR-1 from the CdS baseplate and measure the
resistance value of the VR-1. In this case, the resistance reading should be within the
allowable limit specified in the chart given in Fig 4.2.3.1 [above].
4.2.3.3 Malfunction of the amplifier unit.
In case the voltage at (T5)-(T1) is determined to be normal, the cause can be attributed to
malfunction of the transistors, in which case the amplifier unit must be replaced.
4.2.4 "UNDER" indicator lamp turns on continuously and "OVER" lamp
fails to alight.
This is due to either a decline in (T5)-(T1) voltage to almost 0V caused by shortcircuiting
of the VR-1 or failure of the CdS to provide normal resistance, or malfunction of the
amplifier unit.