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  1. Rleo6965

    Model engineer needs help

    Try this combination of biasing resistor for pnp switch. Hope it will work.
  2. Rleo6965

    Model engineer needs help

    Very good circuit . You maximize your LM358 and eliminated 1pc NE555. You can use PNP for your switching transistor.
  3. Rleo6965

    Model engineer needs help

    Very good suggestion cdrive. Maybe a 10k resistor will do.:)
  4. Rleo6965

    Model engineer needs help

    Maybe you want also to try this diagram delay extender. Notice some similarity with schematic w/ your schematic before?:)
  5. Rleo6965

    Read value of SMD diode (mini-melf)

    I draw red lines in your schematic. This is the possible connection. I can't confirm correctly without the actual board for tracing. Warning. Don't touch big filter capacitor after powering off power supply. 300V charge voltage might still exist. Especially if inverter circuit did not work...
  6. Rleo6965

    Model engineer needs help

    If 358 capable of as +5V for ne555. Upon 358 output goes +5V supplying ne555. Ne555 output remains low for 10 seconds delay and then goes high and remains high. But if 358 goes low. Of course, there's no +5v to supply ne555. therefore ne555 output will be low or 0V. What do you want to...
  7. Rleo6965

    Model engineer needs help

    Are you sure that NE555 will get its +vcc from output of 358?
  8. Rleo6965

    Read value of SMD diode (mini-melf)

    Here's another simple power supply diagram. This will guide to draw correct connections of your diagram. Use ohmmeter to confirm connection. Your making progress.:) The ac signal feedback voltage lower primary winding will drive power transistor to oscillation. Probably 30khz or higher. The...
  9. Rleo6965

    Model engineer needs help

    Hi stew, Maybe its better that you draw first your planned result input and output waveform of your circuit. This will guide you to design circuit of its stages that will comply to input and output required. This I always do. I draw first all the input output waveform to guide me to create...
  10. Rleo6965

    Model engineer needs help

    As steve mentioned. You need to place a 0.1uF in series between LM358 pin1 to NE555 pin2 and connect a 10k pullup resistor. Connect one end of resistor to NE555 pin2 and other end to +VCC. This will create short high to low pulse every time LM358 output switch from high to low. Thus trigger...
  11. Rleo6965

    Model engineer needs help

    Just wondering. What's the purpose of switching T2 transistor on that will results output of IC2 of 29.2 hz of 744us short pulse width? And when T2 was off, the result output of IC2 was 30 hz with 744us short pulse width. Only 0.7hz difference? Can you give specs of RC Servo, so I can...
  12. Rleo6965

    Read value of SMD diode (mini-melf)

    I've googled that 15 watts switching power supply to show that the power transformer winding circuit was similar to your defective power supply. It's only for your guide. I'll try again to draw your schematic again in my free time.. It seems the primary winding and feedback winding for...
  13. Rleo6965

    Read value of SMD diode (mini-melf)

    Tried draw a schematic diagram basing on your posted board. I found out that some traces or drawing were wrong. I think your power supply diagram would be similar to this 15W power supply.
  14. Rleo6965

    Transformer Short Circuit Current?

    What is the frequency of your dc inverter? You don't need big transformer for cdi using high frequency dc inverter..
  15. Rleo6965

    Help me diagnose circuit problem

    If fuse was still okay or not open. Replaced first the 2 electrolytic capacitor with correct value and voltage. Be sure to test terminal of capacitor before desoldering.
  16. Rleo6965

    555 Mosfet driver problems

    I'll wait first for the Vgs voltage test result. :D
  17. Rleo6965

    555 Mosfet driver problems

    Measure Mosfet dc voltage between G and S. Reading of +5V will turn on the Mosfet and lamp. OV should turn off Mosfet and lamp. Place your test probe exactly on Mosfet terminals. Negative probe on S and positive probe to G. This will accurately test voltage on Mosfet and isolate problem.
  18. Rleo6965

    555 Mosfet driver problems

    You need to to pull down voltage in pin4 or reset first everytime you power on your circuit. You can do this by placing a RC circuit. Capacitor and resistor in series. Connect another end of resistor to +VCC and negative pin of capacitor to ground. Then connect pin4 to connection of resistor...
  19. Rleo6965

    Read value of SMD diode (mini-melf)

    To be able to have progress solving your problem. Remember "Know your enemy before you conquer" Draw the primary circuit actual component layout in a legal size paper. Just like it was position in the pcb. Then trace the component connection of pcb draw connection in your drawing. You need to...
  20. Rleo6965

    Read value of SMD diode (mini-melf)

    My last resort to repair that power supply was to reverse engineer the primary circuit portion of the circuit. The result drawn schematic will guide you how to understand the circuit and replaced parts even label was "erased". But this require you a very good background in circuit analysis...
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