Two conventional amplifier stages built with SF215 transistors are linked by ceramic 10.7MHz IF filters, and followed by an FM demodulator built with a TBA120T i.c. Straight from the databook. Output goes via a 100k log potmeter (not shown) to the audio stage. (NB SF215 transistors can be replaced by BF240, BF241, BF254, BF255, BF594 or BF595). Since my junkbox does not contain TIP41s, I made a Japanese version, using 2SC945, 2SA564A and 2SD1138s salvaged from damaged Oriental stereos. The amplifier sounds great and is unconditionally stable.
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The power supply is also made from junkbox parts. A 2 x 12V, 1.5A wall-wart (computer item) feeds a 6800 µF / 100V smoothing capacitor via two BY298 diodes. A Motorola MC78T12CK i.c. (3A regulator in TO-3 package) provides 12V DC. For stability’s sake I placed a 10µF tantalium electrolytic parallelled by a 10nF ceramic capacitor directly between the output terminal of the MC78T12CK and ground.
Audio quality is strongly dependent on the employed loudspeaker. I tried various modern speakers but finally opted for an ancient model salvaged from an empty radio cabinet (Philips AD3700M/06). Valve radio specialist John Hupse (http://www.hupse.eu/radio/speakers/AD3700.htm) lists the following specs for this item: dual-cone, diameter 14 cm, power 6 W, impedance 5 Ohms, efficiency 6%, frequency 90-18,000 Hz, strength of the magnetic field 9,500 Gauss (26,200 Maxwell). It dates from 1961 and is still going strong after 46 years.
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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