The story & manual of DC power supply 1991:10 and 1998:12 (Please see the circuit diagram) The old transformer was consisted by electric metal sheet and coil formers with coils. The metal sheet was cut and formed at Lindab Plåtisol (i.e. Lindab Profil) in Förslöv. This happened in the beginning of October, 1990 and this is the first moment of the DC power supply. At the company of Lindab I got some help, but most of the work I did by my own. In the workshop at home I worked with all pieces and the mains transformer was done in January, 1991. The transformer worked but after a while there was a short-circuit between an uninsulated splice and an other turn of the coil. The mains coil looked something like if you've loaded it too much. But now it worked. The theoretical input power was 80 volt-amperes (VAs), but the practical output was only 63 VAs. Because there are som power dissipations, the metal sheet of trans- former was heated up to a stabilized temperature. The present transformers are bought and each of them has got approximately the same output voltages and powers. The output voltage UL can be regulated between 0 and 30 volts. If UL is near zero and the load current is 2 amps, there will be a high power loss in the serial tran- sistor TIP33A. Of that reason TIP33A is placed on the outside of device box and the transistor has got a thermal connection to a black heat sink. The output voltage UL2: 4 - 8 volts, but the default voltage is 5 V. My thought about the terminal UL2 is that the 5 volts would be the voltage source of TTL circuits, and maximum current is 0.4 amps. The maximum current of terminal UL is 2.0 amps. If the current is 2 amps, the red LED is lighted up. It starts to indicate when the current is 1.7 A or more. Please notice that both of the two negative output polarities, can both be grounded. Some technical specifications: The output resistance of UL is 0.15 ohms. The output resistance of UL2 is 0.9 ohms. The maximum output power of UL is 48 watts. The maximum output power of UL2 is 3 watts. At finally I'm able to mention that this device was finished at August 20th, 1991 (during the great coup of the Soviet Union).   Göran Holbeck Vejbystrand SWEDEN   Back