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  1. Rleo6965

    Read value of SMD diode (mini-melf)

    0.6V was minimal. What was your load? Increase fuse to 1 amp. and place your actual load. Hope your load was not defective.:) If the fuse blow and the fuse glass was not burnt or black. Then possible that fuse capacity was still enough. Replace with 2 amp. fuse and hope it work. If blown fuse...
  2. Rleo6965

    Read value of SMD diode (mini-melf)

    It's possible that FET started the inverter circuit . Test fuse capacity was not enough for the inverter circuit that cause it to blow. Since the FET was not damaged. Replaced the small capacity fuse half the capacity of the original capacity of fuse. What's the original fuse of your power...
  3. Rleo6965

    Help needed to make 555 timer circuit throw relay.

    Try to removed load R4 and LED from NE555 pin3 output for better driving base of npn transistor. You can connect other end of R4 to +9V and other end of LED to collector of 2N2222A. See diagram post by Relayer. His diagram will surely solve your problem.
  4. Rleo6965

    Read value of SMD diode (mini-melf)

    It seems ZD1 was not defective. Some components was pulling down the gate voltage to 1.65V which FET can't conduct. Try to check components connected to gate of FET for possible short or change value. Your schematic for the gate of FET was not complete.
  5. Rleo6965

    My New Toy

    Maybe they will use GPS software of the iphone.:D
  6. Rleo6965

    Read value of SMD diode (mini-melf)

    Solder 3 pcs of ZD1 in series on a wrap w/ insulator like masking tape. Place 2 wire and solder it to location of ZD1. Polarity of zener diode and wiring must be correct. . This will triple the zener voltage value. 4148 was a fast recovery diode. We can't use it as zener diode.
  7. Rleo6965

    Help identifying component on PCB

    If you look closely on this diagram. inductor was connected as signal filter. Even without it. USB device can still have dc power from pin 1 and 4. But of course it will not communicate due to removed inductor. 3rd page...
  8. Rleo6965

    Help identifying component on PCB

    I think that component was for input output signal and not related to power up the usb device hdd interface board. Power pins of usb was on outer pins 1 and 4. Maybe you can try spray contact cleaner on usb port, usb plug. It might work.
  9. Rleo6965

    My New Toy

    Very nice bike. Your doctor gave you good advice. Biking was good for overall exercise for the body. Heart, lungs and legs. But take care biking on the road. Speeding cars and truck was very bad to your health and to your bike.:)
  10. Rleo6965

    Read value of SMD diode (mini-melf)

    If you look close on your schematic diagram. Points 1 and 2 were connected in large value 3 pcs. capacitor in parallel connection. This is the reason that inaccurate reading or charging and discharging of capacitor to your multimeter. Try to replace ZD1 w/ 5,1V or 6V. Be sure that you use...
  11. Rleo6965

    Compatibility serial devices

    You can't directly connect rs232 signal and cmos level signal. rs232 signal have +12V and -12V while cmos was 0-+5V or higher. Even you use cmos w/ +12V signal level. It still can't accept -12V signal. That's the problem hardware side. For the software side. Both 2 device must have same...
  12. Rleo6965

    Read value of SMD diode (mini-melf)

    That value could be the resistance of resistor in paralle with ZD1. But this confirm that there's no shorted component on gate of Power Fet. ZD1 was not shorted . ZD1 will read 0V if shorted both forward and reverse reading. ZD1 2.4V might be okay. It depend on Power FET Gate threshold voltage...
  13. Rleo6965

    Computer Power Unit Failure

    The secondary side was the load side of power supply. An accidental short on its load tends to drop output voltage on secondary side. The PWM circuit will sense this low voltage and and it will compensate it by increasing pulse width waveform of inverter.. Driving more current for the MOSFET...
  14. Rleo6965

    assistance with modifying pc power supply

    Luckily you did not use the +5V dc output. PC power supply shutdown itself if +5 connector have no load.
  15. Rleo6965

    Read value of SMD diode (mini-melf)

    It seems 1.6V was not enough to switch on power fet to conduct or start the inverter. I think ZD1 was the one your inquiring in the first place. Turn off power and test the following component. No need to remove component from board. Using Ohmmeter, test resistance across ZD1. Then set...
  16. Rleo6965

    Computer Power Unit Failure

    One source of shorting Mosfet was defective PWM ic. Can you give the part number of IC?
  17. Rleo6965

    Make a mouse fence that kills mice..in the celing!

    :D You will end up sleeping outside your burnt house together with your mouse. Even you use insulator to your high voltage probe to avoid burning your house. Mouse will not immediately die. because they jump away from the probe because their leg muscle tend to flex when electrocuted. I tried...
  18. Rleo6965

    Help Needed: Building 18V Power Supply for Power Tools

    As BobK mentioned. Buying a Switching power supply with correct wattage was your best solution. But if still you want to build one. The second best option was to use Linear Power Supply with series pass power transistor and big heatsink. Google it and you can find many schematic diagram that...
  19. Rleo6965

    Model engineer needs help

    The reason I placed a 1k pullup resistor in the base of pnp to assure that pnp will completely turn off. I think lm358 high output was not high enough. PNP must be fully turn off and turn on acting as switch or else astable frequency of NE555 will not be accurate. I hope you guys will not be...
  20. Rleo6965

    Model engineer needs help

    Stew, Try replace resistor w/ potentiometer and manually adjust and observe circuit. You should read 0.7V between emitter and base of pnp transistor to be able to turn it on. You should also monitor voltage between collector and emitter. It should read near 1V when pnp was turn on. Temporary...
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