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  1. (*steve*)

    laser ablation of PCB resist

    Hmmmm, I didn't remove the paint on those very well :-( They were done so long ago that the paint had really cured. And I couldn't find any steel wool.
  2. (*steve*)

    laser ablation of PCB resist

    Long time between updates... I'm routinely using the laser cutter to make prototype boards for myself and others. I'm kinda working on a Gerber to go plot file converter to make everything more generalised. But most recently I've been chasing down tinning solutions. I think I posted some...
  3. (*steve*)

    Tektronix TDS3054 data acquisition failure

    A bit of a go-slow on this one. I measured all of the supply rails and none of them have any substantial ripple. I can't comment on them being the correct value, but they seem sensible (+5, +/-15, +3.3, Etc). I haven't checked the outputs of the regulators on the main board. Oh, and the...
  4. (*steve*)

    Centre tapped Transformer

    As best I can tell, he is posting from a place that has 220V (ish) mains. Or more accurately "is no longer posting from..."
  5. (*steve*)

    Identify a burnt resistor

    My guess is that it was originally 39 ohms (orange white black) from the look of the remaining bands. However, this isn't the major problem. Something caused that resistor to overheat. If you replace it, it may just fail again. Also, assuming the original value is something like 39Ω, the...
  6. (*steve*)

    Identify a burnt resistor

    Try measuring it before you remove it. If it's fragile it may break as you remove it. With the aid of a measurement of resistance across 2 points before and after removal we can calculate the resistance if necessary. I recently replaced a resistor that was so fragile it broke *while* I was...
  7. (*steve*)

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Eeek!
  8. (*steve*)

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Check this link. A resistor, a capacitor, and a relay will make an effective time delay (power it from your unregulated DC) and pick appropriate resistor(s) for inrush current limiting. You need to be careful that turning the power supply on while it is connected to a heavy load doesn't...
  9. (*steve*)

    2N2222A current buffer circuit

    That is typically how it's done. You might add a resistor (say 100k) between gate and source to ensure that the MOSFET remains in the off state when power is not applied.
  10. (*steve*)

    2N2222A current buffer circuit

    You place the load between Vcc (or Vdd in this case) and the drain.
  11. (*steve*)

    Arduino Nano LEDs pin failure

    LEDs that have been damaged can exhibit a number of of behaviours short of not working at all: Being dim Exhibiting a turn on delay (can be a second!) Requiring a higher current to turn on. The fact that a LED lights does not mean it's not damaged. In addition, it's possible to damage the...
  12. (*steve*)

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The traditional way of checking for a shorted turn is a "ring test". This essentially involves connecting a capacitor in parallel with the winding, inserting some energy, and watch it ring. The easiest way is to place a charged capacitor across the winding while watching it with an...
  13. (*steve*)

    Correct Motor Help

    Fora is the plural of forum. There are more than one. Check the spoiler in my message above for the information I said I didn't provide (but did) (If you can't figure out the spoiler, the name of the forum I used was "endless sphere".)
  14. (*steve*)

    Series Voltage regulator.

    For a number of reasons, I would connect the base of TR2 to the top of R2 and connect the wiper of VR1 to one end of VR1. However, I suspect that @RaiRodrigues may be supposed to use the circuit unchanged. And do you also need to select appropriate transistors? And do you need to concern...
  15. (*steve*)

    Centre tapped Transformer

    And your mains voltage is 230V?
  16. (*steve*)

    Centre tapped Transformer

    So therefore about 20V across the ends of the windings? What does it measure with the load connected
  17. (*steve*)

    Correct Motor Help

    In that case I won't recommend fora which focus on electric vehicles where you'd find many people with knowledge specific to your questions. I also won't mention that I used them as a resource when modifying my own small electric vehicle.
  18. (*steve*)

    Centre tapped Transformer

    Have you verified that the AC output of the transformer is 9-0-9 VAC?
  19. (*steve*)

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    It can't be the bridge rectifier, because with the secondary disconnected, all there is in the circuit is the transformer. I wonder if you have damaged it
  20. (*steve*)

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The secondary side of the transformer
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