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  1. duke37

    555 Timers

    With some effort, you can tack wires onto a DIP device. You need to be quick to stop them falling off when soldering to the board. Would lead free higher temperature solder help? Or use pliers as a heat sink? You could use a standard socket which could be cooked with impunity.
  2. duke37

    12 V motor loss of power

    The SCR is probably a C106 or maybe an armoured cat fish! 4A. Sensitive gate, very common. The transistors are npn, The 2N3904 is 200mA, The ZTX651 is 2A. Both common. Could the 1R2004 be another 1N4002? It looks as if the 30V AC is rectified with a bridge rectifier and if the motor speed and...
  3. duke37

    12 V motor loss of power

    Please tell us what components are on the board. You have four 1N4002 diodes and another, perhaps the same. You have two small transistors, what are they labelled? You have one big transistor or scr, what is this? The diodes can probably be tested with a meter on a resistance range without...
  4. duke37

    12 V motor loss of power

    Ey oop, welcome to the forum. Show us a picture of the motor and power supply. We need more information. A 27 year old supply should be fixable - no microprocessor. I could help, hands on, if you are not too far from Derbyshire.
  5. duke37

    Understanding impedance

    If you have a voltage divider of 20k and 20k, driven by a low resistance then the output centre tap will appear as a voltage source and a series resistance of 10k. Any load even 10 times the 10k will drop the voltage. 10k will drop the voltage by 50%. 100k will drop the voltage by about 5%, you...
  6. duke37

    Rolson shake torch

    I was asked to look at a Rolson torch which should be shaken to generate energy to light a LED. I wonder if it ever worked as a shake torch. There is a bridge rectifier made from four 1N4007 diodes.This was permanently connected to two CR2032 3V lithium cells and a black cylindrical component...
  7. duke37

    Best solder to use

    "Problem is, what to do with 200g of lead free?" Use it to solder your water pipes.
  8. duke37

    Consumption of a Led Matrix

    You have calculated for 9V so this is the voltage which should be used. At 5.4V only the red led would glimmer. Over 9V the current will be more than 20mA in each string. The more the merrier but the shorter the life. The lower the resistor, the more the current change with voltage so the blue...
  9. duke37

    7809 not outputting 9v

    The most likely fault is that you connected it backwards. A diode is often recommended across the regulator to protect it against reverse current. They don't like it up 'em.
  10. duke37

    Lets talk about fan/blower motors (high vs low)

    Mods, please delete this thread, it is a duplication of another. My replay is still valid but is only a repeat of others.
  11. duke37

    Circuit Element for variable current control

    Put a diode in the output of each voltage source so that the higher voltage one does not bully its little friend. Connect these diodes to a constant current circuit.
  12. duke37

    Lets talk about fan/blower motors (high vs low)

    Unless more information is given, it is difficult to diagnose the problem. What is a DOWNDRAFT stove? Have you got pictures of the damage? If the copper traces on the board have failed, possibly due to a bad solder connection, I would replace them with a wire thick enough to take the motor...
  13. duke37

    Help!! Control module diode identification

    Have you been welding?
  14. duke37

    current limiter for dual rail power supply.

    Half wave rectification is not good, you could use two wall warts with a bridge rectifier for each. Then make two similar isolated supplies which can be placed in series.
  15. duke37

    Adding accessories to component systems

    A 20Ah battery does not deliver 240W, it will deliver what the load needs within reason. A car starter motor takes about 3000W for a few seconds with a battery not much bigger than yours. Add up the current of all the devices. Compare this to the 20A alternator. You will see if there is a lot...
  16. duke37

    current limiter for dual rail power supply.

    You say you have burned out two adaptors. This could be due to the positive and negative output being different. If they are adaptors with a proper heavy transformers then the core can saturate if they have a DC component on the output. A saturated core has very little resistance to input...
  17. duke37

    Honda 3500 watt generator (rotor)

    The rotor has only one winding each end is connected to a slip ring. The rotor is fed with DC not AC. The voltage/current/wire size/wire turns will depend on the design. I do not think the the number of turns is critical, the controller should provide what is necessary to get the required output...
  18. duke37

    How to get a certain duty time

    It is necessary to control the capacitor charge AND discharge. Here is a circuit but it is wrong, one diode should be the other way round.
  19. duke37

    P=I*R

    P = I*I*R NOT P = I*R P = I*V P = V*V/R
  20. duke37

    High Low logic

    The TL331 is a comparator and does not have a voltage reference.
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