The diagram below shows that power supplies don`t have to be complicated, especially in low-power designs. The filaments are powered directly from the 120 volt AC line, minimising the size of the transformer(s) required to drive the amplifier. Note the slightly unusual series-parallel arrangment; each pair of 35C5 output tube filaments is in series with one half of the 12AU7 dual triode. The center-tap of the 12AU7
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sums the two branch currents (150 mA each) into the preamp tube, giving 300 mA as required for this valve`s heater supply. While unusual, this geometry is eminently stable and safe. If any tube is removed (or its filament burns out), none of the others will suffer as a result, unlike some series-wired television sets where a single burnout could take out several other tubes at the same time. Each branch of two 35C5`s drops 70 volts. Add in the 6V drop across each half of the 12AU7, and the 9V drop across the 9JW8 input tube, and we have 85 volts. The two dropping resistors R1 and R2 each drop 36 volts (150 mA x 240 ohms = 36 V), for a nominal line input voltage of 121 volts. Because of this dependance on 120 volt line voltage, this design is unfortunately not practical for 240 volt AC supplies. Incidentally, the two dropping resistors get quite hot during normal operation. I suggest cementing them to the chassis, and placing a small heat-sink on the other side to help dissipate the generated heat. The heatsinks supplied with fans for 486 processors are perfect for this. (. just in case you wondered what the CPU heatsink was doing in the pictures!) The B+ supply is very conventional, consisting of a small plate transformer (150 volts either side of center-tap), a full-wave rectifier, and typical CRC filtering networks. The idea here is to get approximately 165-200 volts DC at the first filter output (B1) at quiescent...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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