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VPP Problem

Mohammed
2014-10-18
2014-10-18
  • Mohammed

    Mohammed - 2014-10-18

    Sir, I have finished the programmer baseboard. and tested. It's ok for EEPROM(24C02) but it's not recognizing pic. I tested the voltages and found there is only 5.6v in the vpp pin. So I changed the inductor to a higher value , still the voltage increased a little.(0.02v) I am using diode 1N5819. then I removed the 100uf/25v capacitor(C1). tested the voltage with out capacitor. amazing it's 14.5v then I replaced the capacitor with a tantalum (22/25v) but still the result is same as before(vpp=5.6v) Then I reduced the capacitor value to 1uf/25v tantalum, still the vpp is not increasing, So I removed the capacitor and tested the board with a pic 16F676, it's now recognizing the pic but can't write or read because so many errors. please help me to solve issue, thank you.

     
  • Mohammed

    Mohammed - 2014-10-18

    Finally I solved the issue, all the problem raised from R1 and R2, I used 10K and 5.6K instead of 22K and 12K. that was the reason of malfunctioning. when i replaced the resistors as in original circuit, it worked. I used 22/25v tantalum for C1.hope it may help others. thank you

     

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