Search results

Search Forums New Posts
  1. WHONOES

    CTEK MXS 3.8 repair

    If the FET is being switched, which it probably isn't otherwise the unit would likely be working, you should be on ac. Having said that, you probably wouldn't see anything as the gate signal will be at several tens of KHz which your meter won't be able to resolve. You could make a simple...
  2. WHONOES

    PWM issues when powering 4pin 12v fan without a motherboard

    I think the 12V on the fan pin 1 should be constant i.e. wired direct to you PSU with the controller connected as suggested. I expect the controller is intended to control a motor directly whereas the fan just want a PWM signal to do the deed. Edit: As an after thought, the controller may need...
  3. WHONOES

    PWM issues when powering 4pin 12v fan without a motherboard

    Have you tried connecting the fan ground through the controller unit leaving out the extra connection from the fan to your PSU?
  4. WHONOES

    CTEK MXS 3.8 repair

    336V on the drain suggests your mains is about 237V. I that correct? Let us know how you get on.
  5. WHONOES

    How to choose the correct potentiometer?

    30mA through the pot suggest it value is 330Ω and not the 25K you originally quoted. Current thru 25K at 10V supply = 250μA. Another thought, do you have the pot connected correctly?
  6. WHONOES

    How to choose the correct potentiometer?

    The datasheet claims that the units are supplied with a pre-wired potentiometer. I would suggest you use that and follow the installation instructions. It also seems to infer that the control voltage is generated within the fan unit and that you just need to connect the pot in the correct manner.
  7. WHONOES

    CTEK MXS 3.8 repair

    The 2F mark is smd shorthand for variations on the old 2N2907A but in a SOT-23 package. The ones I have found are FMMT2907A. KST2907A and MMBT2907A. You could try replacing that for a start. My preferred method for removing such devices is to cut through the legs as close to the body of the...
  8. WHONOES

    CTEK MXS 3.8 repair

    You could in the first instance try replacing the FET and see what happens. Also, as a bit of an after thought, is there a resistor in series with the FET gate?
  9. WHONOES

    How to choose the correct potentiometer?

    You could be using a Log pot when you should be using a Lin pot. Also the value seems a bit high. It depends on the input resistance of the controller you are using. What make and type is it?
  10. WHONOES

    CTEK MXS 3.8 repair

    The gate of the FET should have a square wave signal on it. If not, the drive circuit or the FET has failed. If you have access to an oscilloscope, remove the FET and see if there is a signal on the gate pad. Take care when poking around on a board like this as the voltages present at lethal.
  11. WHONOES

    Switching a RF signal

    Agree with you. Relays on a pcb would require transmission lines for proper integration. Ok if you know how to design them correctly. Like you, I have always subscribed to the KISS principle. For those who may not be familiar with the acronym it means Keep It Simple Stupid.
  12. WHONOES

    Capacitor neutralization circuit not discharging

    Still don't understand what you are trying to do.
  13. WHONOES

    Electronics Parts in Calgary, Alberta ?

    It pays to be pragmatic.
  14. WHONOES

    Wire a mag drill motor

    Why don't you ask the manufacturer / supplier what to do with it?
  15. WHONOES

    PWM LED DImmer

    You have to mine all the way to the bottom of the spec sheet where it tells us that PWM (dimming control) pin requires 0.5 to 2.5V with respect to 0V to effect the dimming function. You could conceivably pot down the power supply to give the required voltage range.
  16. WHONOES

    Switching a RF signal

    Absolutely.
  17. WHONOES

    Beware of tunnels in Greece

    That should fit.
  18. WHONOES

    LED Strip from coin cells

    You can run LED's from ac. You just put a reverse connected diode in parallel with the LED plus the usual series resistor. You must also take into account the peak value of the ac voltage, which is going to be 1.4 time whatever the transformer says, when calculating your resistor. You will get a...
  19. WHONOES

    Switching a RF signal

    Depends on how much degradation you are prepared to put up with.
  20. WHONOES

    Electronics Parts in Calgary, Alberta ?

    Somewhere nearby is always going to be preferable.
Top