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  1. ei! about the schematic ante posted, the Q1's emitter must be connected to 0V... ok?........
  2. ei! help me with circuit.. i want to change the semiconductors...will you please suggest a substitute for this.. tnx!! Resistors (all 1/4W 5% carbon film) R1,R9 1k (brown, black, red, gold) R2,R10,R11 470R (yellow, purple, brown, gold) R3,R13 10k (brown, black, orange, gold) R4 1M (brown, black, green, gold) R5 2k2 (red, red, red, gold) R6,R8,R15 220R (red, red, brown, gold) R7 10R (brown, black, black, gold) R12 560R (green, blue, brown, gold) R14 100R (brown, black, brown, gold) R16-R23 330R (orange, orange, brown, gold) Capacitors (electrolytics 2.5mm spacing, others 5mm) C1,C4,C6 100u electrolytic 16V C2,C5,C7 220u electrolytic 16V C3 100n miniature polyester C8,C11 100n ceramic C9,C10 22p ceramic Semiconductors TR1,TR3,TR4 BC549B npn transistor (or BC547B, 48C etc.) TR2 BF244A or B N-channel JFET TR5 ZTX313 npn switching transistor D1-D3 1N4148 silicon diode D4 BAT42 Schottky diode REG1 LP2950 5V regulator IC1 18-pin DIL socket + PIC16C54 HS/P microcontroller DISPLAY1,2 0.56" dual 7-segment LED display, common cathode Miscellaneous X1 20MHz crystal, HC-49/U case S1 miniature pcb vertical slide switch, SPDT INPUT BCN pcb socket BATTERY PP3 battery snap 4 x rubber feet ...... below is the schematic..... frequency_counter.pdf
  3. hello!.. i haven't buy this power supply.. i got the schematic somewhere on the net... i want to modify it so that it will produce more current... (read the pdf for more info on the original schematic) pls help me modify it....;) tnx!
  4. Hello!!! Here is a schematic that I want to modify... I want the 0-20 (3A) to become 5A 0-40 (1.5A) to become 2.5A Any suggestions?.... tnx!!! xp-750.pdf
  5. ei!! -- is there a short protection circuit here?... when i accidentally short the output terminals, is it ok? what will happen again???.. :) -- how to measure the load regulation and line regulation? ---can i use one transformer rated 30V 10A to X2 of the circuit?... because i will make dual supply.... tnx!
  6. okie!!! tnx mr audioguru!!.. another clarifications: -- about the modified schematic, do you think, theoretically, will it work?... --when i short the Positive and Negative of the output, what will happen? --where will i put again the "power on" indicator?(possible ways) tnx!!
  7. ei der!! i have read all the posts.. and they modified the power supply... i have a question, where will i connect RV1? to pin 6 and pin 4 or to the Null?... -- just to clarify: - is the emitter of Q1 only grounded? - has anyone tried the unmodified schematic? because someone said in the first part of the forum the it is working? - for what is the changes?.. the TIP31, transfo.. etc... ----sorry for the english ----- tnx!
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