Power supply for the transceiver from an AT/ATX computer power supply. Part 2. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Computers
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In the spring of 2001, UA3DJG published an article in Radiohobby magazine "about the use of a power supply unit from a computer. Alteration takes about an hour, including assembly and disassembly. I want to share my experience in making such a power supply unit and "complement" the author's article.
Rice. 1 Schematic diagram of alterations.
New items are shown in red.
I used a PSU that says 230W PEAK LOAD. It turned out that he was not suitable for a quick rework. Below is a step-by-step instruction for alteration:
- Unsolder all wires coming from the outputs of other sources (-5 V, -12 V, +5 V), except for the common (GND) and +12 V.
- Fold the remaining wires into bundles. With a yellow beam (+12 V), make several turns on a ferrite ring (2000NM, 25 mm in diameter), and then, together with a black one (GND), connect respectively to the "+12 V" and "-12 V" terminals installed in place of the socket for monitor connection. Connect a 33uF x 25V capacitor in parallel to these terminals.
- The hole in the case, through which the power wires went out, was used to install a key switch (-220 V) with backlight (previously file the hole into the desired shape).
- Replace the +12V source rectifier diodes (two diode assembly on the heatsink - shown in red on the Fig. 1) on KD2999 (2 pcs.) with any letter by installing them on the corner (TNX RV4HV) and fix it on the radiator by soldering the extension wires to the diode leads (Fig. 2). It is even better to use here an assembly of diodes with a Schottky barrier 25 A x 100 V - less voltage drop and, accordingly, heating.
- Capacities 220 x 200V replace with 330 x 350V. Since the capacitors differ from those installed, they are soldered on legs from the wire.
- The output capacitance "+ 12V is replaced by 4000,0 x 16V. To reduce the voltage on the fan, it is necessary to include diodes in the power circuit. Diodes in the + 5V circuit are located at the bottom of the printed circuit board.
- To increase the output voltage from 12 to 13 volts, it is necessary to break the printed conductor coming from the middle point of the +5 V rectifier assembly and connect any 1..2 A silicon diode in direct connection to this circuit, as shown in Fig. 1 (D*). The author used KD226. After that, the transceiver began to give its "native" 100 W to the antenna (at 12 V -80 ... 90 W). The specified circuit supplies a feedback voltage for the output voltage stabilization stage; reducing this voltage with a forward-biased diode by about 0,6 V led to an increase in output voltages, incl. and source +12 V to +13 V; instead of a diode, you can also use a resistor, choosing its resistance to get +13 ... + 13,5 V.
Fig. 2
Fig. 3
The result was a power supply unit with the following parameters: Uout - 14,2V at a load current of 20A, light (weight about 700 g), small (80x100x150 mm), reliable power supply with short circuit protection. at the output (10 times "short" the output with a piece of wire - it just turned off). The output voltage changes by no more than 30...40 mV when the mains voltage changes from 180 to 280 V. There is no spurious signal modulation during transmission. At idle, it consumes about 7 watts from the network. Efficiency when the load current changes from 5 to 20 A within 80 ... 85%. The unit has been in operation since May of this year at the dacha. The mains voltage during the day can vary from 195 to 235V, but it does not affect the quality of the FT-840. When compared with the PSU assembled according to the usual scheme, no differences were noticed.
Author: Nikolay Shadrin, RZ4HX, rz4hx@infopac.ru; Publication: cxem.net
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