Yashica TL Electro-X Service Manual

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Yashica TL Electro-X Service Manual

Table of Contents

Foreward

1) Principles of Operation

o 1.1) Exposure readout circuit

o1.2) Shutter Circuit

Principle of variation of the shutter speeds

Bulb exposure

o1.3) ASA Film speed setting

2) Electical diagrams

oSchematic diagram

oWiring diagram

3) Testing and measuring instruments

oVoltage stabilizer

oInsulating resistance meter

oFocal plane shutter tester

oStandard light source

4) Method of Repair

o4.1) Battery checker circuit

4.1.1) Battery checker lamp fails to turn on

4.1.2) Improper voltage range

o4.2) Malfunction of the exposure readout circuit

4.2.1) Both the "OVER" and "UNDER" indicator lamps fail to turn on

4.2.2) "UNDER" indicator lamp turns on normally, but "OVER" lamp fails to light, or "OVER" lamp functions normally, but "UNDER" lamp fails to turn on.

4.2.3) "OVER" indicator lamp turns on continuously and "UNDER" lamp fails to turn on.

4.2.4) "UNDER" indicator lamp turns on continuously and "OVER" lamp fails to alight.

4.2.5) Adjustment of the exposure readout circuit.

o 4.3) Shutter circuit o 4.3.1) Shutter speed

o 4.3.2) Shutter remains open

o 4.3.3) Shutter closes automatically at "B" setting o 4.3.4) Adjustment of the shutter speed

Foreward

This manual contains matters necessary for repair and servicing of the Yashica TL Electro-X.

The Yashica TL Electro-X incorporates the following functional features which make it completely different from other focal shutter single-lens reflex cameras:

1.Thru-the-lens exposure readout system which does not require an exposure meter and provides measurement of the correct exposure at stopped-down aperture through preselection of either the lens aperture or shutter speed.

2.Electronic-controlled focal plane shutter affording an infinite range of intermediate shutter speeds (and providing faithful function at 1/1000 sec. even when battery power is exhausted).

Its exposure readout and electronic shutter systems follow the pattern of those featured in the Lynx5000E (14E) and Electro 35, and their merits are outlined in their respective repair manuals. Generally speaking, therefore, the Yashica TL Electro-X can be said to be an equipment which offer all advantanges of the above-mentioned cameras.

Principles of operation

The circuitry of the Yashica TL Electo-X can be generally classified into the exposure readout circuit, shutter circuit and battery checker circuit. The exposure readout circuit and the shutter circuits are linked to each other with the aid of a slide resistor.

A coaxial dual variable resistor is employed for this purpose. Its top section forms the balancing resistor (VR-1), while its bottom section functions as the shutter speed resistor (VR-2).

The circuit pattern consists of a combination of the exposure readout circuit of the Lynx-5000E (14E) and the shutter circuit of the Electro 35, and correlation between the functions of these two circuits is maintained through incorporation of the variable resistor.

1.1Exposure Readout Circuit

The intensity of the light controlled by means of the diaphragm (exposure reading through stopped-down) is sensed by the two CdS sensors incorporated in the pentaprism housing on both sides of the viewfinder eyepiece.

Being a photoconductive cell, the CdS serves to vary the resistance value at a ratio inversely proportional to the intensity of light to which it is exposed.

Because the CdS and the BALANCING resistor (VR-1) are series connected, the voltage from the power supply is affected by the degree of resistance offered by both and the voltage equivalent to the VR-1 is applied to (T5)-(T1).

Both the OVER and UNDER indicator lamps fail to turn on (indicating correct exposure) when the voltage range at (T5)-(T1) is between 0.6 V and 1.0 V. The OVER indicator lamp turns on when the voltage rises above this level and the UNDER indicator lamp alights when it falls short of this range. Consequently, the procedure for setting the correct exposure (indicated by the OVER/UNDER lamps failing to turn on) consists of adjusting the VR-1 to a setting where a voltage supply of 0.6 V to 1.0 V will be maintained at (T5)-(T1) as against the CdS resistance value.

1.2Simultaneously with the setting of the resistance value of the VR-1 through exposure readout, the shutter speed resistor (VR-2) which is set coaxially is adjusted accordingly.

a.The trigger switch (SW-5) is adjusted to "ON" position when the shutter is charged. b.When the shutter release button is depressed, the power switch (SW-2) on the shutter side is

turned on, setting the power supply to the circuit. At this stage, however, the Tr6 and Tr7 are at "ON" position because Tr5 is turned off. Consequently, the magnet functions to hold the rear sector of the shutter.

c.At the next stage, the trigger switch is turned off and the electric current controlled by the setting of the shutter speed resistor begins to flow and the charging of the condensor C1 starts. Immediately after the trigger switch is turned off, the front shutter sector is activated mechanically and starts its function.

d.The electric potential of the condenser C1 rises gradually and, when it reaches a given (approx. 2.4 V), the Tr5 turns on and, simultaneously with this, the Tr6 and Tr7 are switched off. This cuts off the supply of electric power to the magnet which then loses its force of attraction, causing the rear sector to commence operation.

e.As soon as the rear sector completes its run over the entire picture area, the SW-2 is turned off, thus cutting off the supply of the electric power to the shutter circuit and completing the shutter operation.

Principle of variation of the shutter speeds

The shutter speed is decided through setting of the shutter speed resistor (VR-2).

If, for instance, only a very low resistance is offered by the VR-2, a large flow of electric

current is supplied to the condenser C1, necessitating only a very short period of time to charge it to full capacity. In other words, the terminal voltage of the C1 rises to a given value within a very short period of time, causing the rear sector to start to function with hardly any time delay and thus providing fast exposure. If, on the other hand, a high resistance is offered, a restricted flow of electric current is supplied, requiring a considerable period of time before the terminal voltage of the C1 can reach level and thus providing long exposure.

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.

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