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  1. dorke

    MOSFETs' source-drain resistance

    NO, What you need is the 4 diodes. It may be the case that they are the MOSFET internal ones...
  2. dorke

    Gate driver datasheet for IGBT

    That depends on the load type you are driving, and the specific IGBT you are using. Please post a diagram and details.
  3. dorke

    dual power supply for large countdown timer?

    Yes, absolutely. You can also add a protective fuse , and a series schottky diode to protect against reverse polarity, both on the "timer -leg".
  4. dorke

    More Range From 10 turn POT

    There is another thing you can try set R1 to 240ohm. It will double your "turn ratio". BTW, an odd point, The LM338 is capable of 5A, yet you are using a 2A transformer, why is this?
  5. dorke

    Low Intensity LED Array

    The voltages Vi=5 and VL=12 are fine. But, you do have a problem with the LED here power disipation: You are too close to the PD=160mW, if you work the led constanttly on with 100mA! "When you say Vout of the LED chains to be +0.6V above what is needed you do mean the voltage at the cathode...
  6. dorke

    More Range From 10 turn POT

    Yes it is advised to add the protection diodes. What are you going to use this P.S supply? Fixed voltage with "fine adjustment"? Variable output voltage?
  7. dorke

    dual power supply for large countdown timer?

    The simplest SPDT switch to select the source of the 12VDC to the timer.
  8. dorke

    Replacing A5sHB transistor (netbook)

    The A18I must be a DC/DC (step-down?) converter,I can't identify it. Without the battery, please measure: 1.The resistance from the cathode of D1 to GND. 2.The resistance of all V-points to GND.
  9. dorke

    Killing SSR (relays) - Need to understand

    1) Have you measured the heater current? 2)have you measured the SSR case temperature? 3) What type of SSR are you using (brand, model, datasheet)? 4) You hoist a Canadian flag, isn't your line voltage at 120V? how come you have a 240V heater?
  10. dorke

    Low Intensity LED Array

    "From the equation given in "Setting the Channel Voltage" what is VFB? Is it .6V as I quoted in my original post?" VFB is 0.3V(typ.) an internally regulated voltage. you use it to set the 0.6V needed(see below) "In selecting Vl I assume I must be considerate of the voltage drop across the...
  11. dorke

    Replacing A5sHB transistor (netbook)

    1) The connection of D1 and D4 makes no sense , please re-check. 2) Please check the resistance from D1 cathode to GND. 3) Please check D1 in diode test mode (both directions). 4) Is there anything else written on the "A181" device".
  12. dorke

    Replacing A5sHB transistor (netbook)

    Please,a clear photo of the area with the white trace .
  13. dorke

    Low Intensity LED Array

    Look on page #10 of the datasheet for details. answers: 1. With R2 and R3 "ratios" 2. With R2 and R3 absolute values (higher for low current). 3. a) NO,it is only for fault detection in a LED string. b) You know about the max and min from the LEDs in the string. For max take the 1.6V(spec-ed)...
  14. dorke

    Replacing A5sHB transistor (netbook)

    1. The 0.2v on the cathode of D1 is suspicious. looks like it goes to the other side of the board through those 6 vias ,can you trace that connection. 2. Try to trace the 4.12V from the 000 ohm resistor. 3. Taking another look on the other side of the board , I see what may be test points for...
  15. dorke

    Replacing A5sHB transistor (netbook)

    Please measure the yellow arrows and mark the other ss24 diodes.
  16. dorke

    Diode HUGHES R 275

    If it is just for a "mockup thing " you can buy Hugues diodes on the web. Here is one for example and another
  17. dorke

    Replacing A5sHB transistor (netbook)

    Please mark the direction(cathode line) of D14 on the photo.
  18. dorke

    Replacing A5sHB transistor (netbook)

    Please,measure the voltages on the 4 green arrows on the photo. Only with battery connected(no adapter) All measurements should be related to GND.
  19. dorke

    Reactance Question

    The units of reactance is indeed ohm units , like that of a pure(real) resistor. But reactance is an "imaginary" resistance not a "real" one. i.e. real and imaginary in the sense of the impedance plane. Like so: As mentioned before the X(reactance) values are dependent on frequency. For a...
  20. dorke

    Green LED power consumption

    In this case, try using a high efficiency 2ma LED
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