power supply am farm radio

Posted on Feb 6, 2014

The affection of the ability accumulation is a Tamura 3FD-410 5V bifold primary/dual accessory transformer. These are accessible from DigiKey. com for reasonable prices. Normally, the transformer`s primary windings would be affiliated in alternation for 240VAC operation or in alongside for 120VAC operation. This ambit takes one of the primaries and

power supply am farm radio
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repurposes it as a 120VAC secondary. For this to work, the agent should be somewhat over-rated, which it is in this case. The two 5V accessory windings are accumulated in alongside and beatific to a arch rectifier and clarify capacitor to aftermath about 7VDC. This DC voltage is current-limited by a 150 ohm resistor and acclimated to drive two amber LEDs. The LEDs can be hot-glued to the central of the radio aloft the punch to accommodate punch lighting and power-on indication. The 7VDC is additionally beatific to an LM317 adjustable voltage regulator IC. The LM317 commonly produces a minimum voltage of 1. 7V, which is too aerial for this application. A alternation 1N4002 diode is acclimated to bead about. 5V to aftermath a minimum voltage of 1. 2V. The regulator is adapted so that the filaments accomplish at 1. 5VDC. The 90VDC B+ accumulation uses a arch rectifier beyond the transformer`s additional primary ambagious to aftermath about 160VDC. The rectified DC is filtered through a brace of electrolytic capacitors and a alternation resistor. The resistor drops the B+ voltage to the appropriate 90V.

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