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  1. Cirkit

    433MHz door bell - Tx antenna feed

    Thanks Martin, do you think it could be the SAW resonator (circular metal can) failing? The problem with the bell push seems to be worse when it's raining. The bell push has been fine for many years so I doubt whether the antenna needs improving.
  2. Cirkit

    433MHz door bell - Tx antenna feed

    I'm having problems with the same doorbell again! Better photos of the PCB attached. Seems to work fine when the receiver and bell push are fairly close. I have tried new batteries in both. I've also resoldered the joints on the bell push PCB and some on the chime receiver. How can I test...
  3. Cirkit

    Am i testing it right

    It seems that the switch is closed when the door to the equipment is closed. It's odd that the positive output of the power supply is connected to the chassis?
  4. Cirkit

    Resistor to discharge capacitor

    I agree that is good practice, but not all SMPSs have them and if there is a fault rather than the capacitor being discharged on power down, the terminals remain at high voltage.
  5. Cirkit

    Resistor to discharge capacitor

    I had a 60W incandescent one to hand and tried that which discharged a 4.7μF capacitor with a little crackling sound! I'd like to make a discharging tool with probes and a resistor. Could I add a neon in parallel or would it need a dropper resistor?
  6. Cirkit

    Resistor to discharge capacitor

    Thanks for all the replies, the 220Ω was just a low enough figure I thought would allow a fairly fast discharge without leaving the probes on for too long. I will use something in the low kΩ range and use insulated probes of course.
  7. Cirkit

    Resistor to discharge capacitor

    Ah no sorry for the misunderstanding. I meant when repairing, just discharging the capacitor so that the board is safe to work on.
  8. Cirkit

    Resistor to discharge capacitor

    Yes, I did calculate it to be around 700W but that would be continuously. For a short mS discharge, surely a lower wattage resistor would suffice?
  9. Cirkit

    Resistor to discharge capacitor

    What is a suitable resistor to safely discharge a large main filter capacitor ~400V found in SMPSs? Would a 220Ω 2W resistor be too small in value?
  10. Cirkit

    Buzzing Makita DC1414 F charger

    Thanks for uploading the spectrum @Harald Kapp. @Martaine2005 do you have any suggestions which capacitors I should replace? Is it likely to be the main filter capacitor?
  11. Cirkit

    Buzzing Makita DC1414 F charger

    I have the above Makita charger which is buzzing with a variable frequency when the green LED flashes. I have tried prodding the transformer and various components but the buzzing doesn't stop. I don't want to start replacing capacitors on the chance that may cure the buzzing. Attached are...
  12. Cirkit

    Sauna Steam Generator - Bypass ne555 timer?

    The 60 minutes is most likely for safety if the steam generator is designed for a sauna. Can you post close up photos of the circuit including ICs?
  13. Cirkit

    Power line adapters

    Are you plugging any of the power line adapters into power strips or surge protected sockets? They should be plugged into socket outlets directly. Also, do you know if all the adapters are on the same electrical circuit/breaker?
  14. Cirkit

    Need help with a failed controller for a treadmill.

    When you tested the sensor removed from the treadmill with another magnet on the bench, you used continuity mode on your multimeter. Can you try using the 200 Ohm range or continuity (beep) mode and testing again.
  15. Cirkit

    Need help with a failed controller for a treadmill.

    That's why I suggested rotating the drive pulley manually (in #10) to see if you can register when the magnet passes the reed switch.
  16. Cirkit

    Soldering Iron power supplies ... repairs etc.

    I find with the cheaper/clone soldering stations that the tip temperature does not accurately match the set temperature. Some of the more expensive brand soldering stations track the tip temperature and provide additional power to account for loss of heat into the joint. You may want to check...
  17. Cirkit

    Need help with a failed controller for a treadmill.

    OK, so you replaced the parts like for like. If you place your meter across the sensor contacts and manually rotate the fly wheel, do you register any change in reading? It would be worth investing in an ESR tester if you can. You can buy cheaper ones that do not have a built-in rechargeable...
  18. Cirkit

    advantage and disadvatnge of AC to DC converter circuit

    Using a plug-in power supply as has already been mentioned would be far safer. You should be able to pick up a small 12V one or order online.
  19. Cirkit

    advantage and disadvatnge of AC to DC converter circuit

    The small fan isn't going to have much effect in the fridge. You'll just be blowing the cold air towards one surface. Do you intend to connect the fan to the fridge thermostat? It might be easier to use a mains powered fan instead as mentioned above.
  20. Cirkit

    Need help with a failed controller for a treadmill.

    What were the part numbers of the original rectifier and IGBT? Do you have an ESR/component tester? You can buy a fairly cheap one and worth having.
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