1995 Volvo 850 Turbo Replacing the Radiator Fan Belt on the 1995 Volvo 850 Turbo

Is the fan that is located in the motor of a fan in 1995 Volvo 850 Turbo, a radiator fan belt? How to replace it?

Answer: No. The car, the Volvo 850 is powered by a transverse engine, the radiator and the fan are mounted across the front and they are driven directly by the motor.
However, at the end of the engine the belt that was once called the fan belt is still there in your car. It doesn’t drive the fan, like it did in older cars (and still does in many longitudinally-engined cars), but it will drive the alternator, water pump, power-steering pump and (if fitted) air-conditioning compressor. Many people still refer to this belt as the fan belt, although the correct term is accessory drive belt.

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2005 Chevrolet Malibu Maxx Cost and Processes in Electronic Power Steering Control Check on 2005 Chevrolet Malibu Maxx

The shop can’t get a 4 wheel alignment for my 2005 Chevrolet Malibu Maxx because the steering is pulling and I needed to get the electronic power steering control checked. What are in the repairing process and how much does it cost? Thank you in advance.

Answer: Almost all electric power steering system check in your 2005 Chevrolet Malibu begins with 1 hour of diagnostic time. Once the fault is determined, the repair shop can estimate the cost for any necessary repairs. Please, get your electric power steering system diagnosed and repaired in a qualified repair shop.

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Music On Hold for Telephones

Here is a simple circuit for music-on-hold with automatic shut off facility. During telephone conversation if you are reminded of some urgent work, momentarily push switch S1 until red LED1 glows, keep the telephone handset on the cradle, and attend to the work on hand. A soft music is generated and passed into the telephone lines while the other-end subscriber holds. When you return, you can simply pick up the handset again and continue with the conversation. The glowing of LED1, while the music is generated, indicates that the telephone is in hold position. As soon as the handset is picked up, LED1 is turned off and the music stops.

Music-On-Hold for Telephones Circuit diagram :

Normally, the voltage across telephone lines is about 50 volts. When we pick up the receiver (handset), it drops to about 9 volts. The minimum voltage required to activate this circuit is about 15 volts. If the voltage is less than 15 volts, the circuit automatically switches off. However, initially both transistors T1 and T2 are cut off. The transistor pair of T1 and T2 performs switching and latching action when switch S1 is momentarily pressed, provided the line voltage is more than 15 volts, i.e. when the handset is placed on the cradle. Once the transistor pair of TI and T2 starts conducting, melody generator IC1 gets the supply and is activated. The mu-sic is coupled to the telephone lines via capacitor C2, resistor R1, and the bridge rectifier.

With the handset off-hook after a ring, momentary depression of switch S1 causes forward biasing of transistor T2. Mean-while, if the handset is placed on the cradle, the current passing through R1 (connected across the emitter and base terminals of pnp transistor T1) develops enough voltage to forward bias transistor T1 and it starts conducting. As a consequence, output voltage at the collector of transistor T1 sustains for-ward biasing of transistor T2, even if switch S1 is released. This latching action keeps both transistors T1 and T2 in conduction as long as the output of the bridge rectifier is greater than 15 volts. If the handset is now lifted off-hook, the rectifier output drops to about 9 volts and hence latching action ceases and the circuit automatically switches off.

EFY lab note. The value of resistor R2 determines the current through resistor R1 to develop adequate voltage (greater than 0.65 volts) for conduction of transistor T1. Hence it may be test selected between 33 kilo-ohms and 100 kilo-ohms to obtain instant latching.) The total cost of this circuit is around Rs 50.

Source : http://www.ecircuitslab.com/2012/02/music-on-hold-for-telephones.html

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On And Off Button Circuit

In this simple circuit we give the chip a little more attention than usual. It is astonishing what can be built with a 555. We are always infatuated with simple circuits using this IC, such as the one shown here. The 555 is used here so that a single push-button can operate a relay. If you press the button once, the relay is energized. When you press it again the relay turns off. In addition, it is possible to define the initial state of the relay when the power supply is switched on. The design is, as previously mentioned, very simple. Using R1 and R2, the threshold and trigger inputs are held at half the power supply voltage.

Circuit diagram:

On/Off Button Circuit Diagram

When the voltage at the threshold pin becomes greater that 2/3 of the power supply voltage, the output will go low. The output goes high when the voltage at the trigger input is less than 1/3 of the power supply voltage. Because C2, via R3, will eventually have the same level as the output, the output will toggle whenever the push-button is pressed. If, for example, the output is low, the level of the trigger input will also become low and the output will go high! C1 defines the initial state of the relay when the power is applied. If the free end of C1 is connected to Vcc, then the output is high after power up; the output is low when C1 is connected to ground.

Author: Ger Langezaal - Copyright: Elektor Electronics

Source : www.extremecircuits.net

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