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  1. kellys_eye

    Opto Coupled Tunable Coil Circuit - Comments Please

    All you've achieved is a 'buffer' circuit with isolation. Assuming you could get a variable capacitor to tune to 2Hz with the chosen inductor (good luck with that) you can 'peak' the resonance - which isn't really required as the driver transistor doesn't require it. On the output side you...
  2. kellys_eye

    Can anyone suggest me high quality electronic manufacturing products provider?

    Let me guess - you're about to give us a 'good example' yourself?
  3. kellys_eye

    High power PSU have more extra transformers than the main one

    Some PSU's have a 'standby' voltage that is also created in an SMPS-type of manner hence the 'extra' transformer. You might also find miniature versions used to isolate feedback signals and even used to drive switching transistors (driver transformers). There is no 'standard' so each case has...
  4. kellys_eye

    POT burning/candle-like smell

    Even wired correctly it is on the limit of its wattage capability.......
  5. kellys_eye

    laster and LED ligth for meter saw

    Lasers generally use a constant current source - the cheap penlight lasers are often powered using silver-oxide batteries using their own internal resistance as a current limiting factor. Purely for the sake of safety (yours) I'd recommend you use a simple 'keyring' laser and mount it...
  6. kellys_eye

    Connecting a LED directly to a 230v isolation transformer

    You'd need a 10W resistor to be safe......
  7. kellys_eye

    how to create autoswitching circuit for 12v ups for router

    Simple blocking diode if the difference between the battery and adapter voltage is 0.7V or so.....
  8. kellys_eye

    Battery charger not charging

    Those simple chargers rely on the battery as the 'smoothing capacitor' - they are basically a transformer and bridge rectifier whose output voltage (without the 'smoothing') is around 10V. Connect a WORKING battery (capacitor) and the voltage will rise to the 13.8-14V range to affect a charging...
  9. kellys_eye

    Inverter for 240v 20w fluorescent lamp

    There are small inverters commonly used to power fluorescent tube lights - many of the older type 'emergency exit' lights have them fitted - that could serve the purpose. You do, of course, need one designed for a 20W lamp. Here's one (not a particularly good example due to the use of a...
  10. kellys_eye

    Vintage Sharp RT-3388a digital tape counter not counting

    Extra - check the belt between the pulley and magnet (item 6 and 12 on page 11) - it might be snapped.
  11. kellys_eye

    Vintage Sharp RT-3388a digital tape counter not counting

    The turns counter is a hall effect device (IC5) fitted to the back of the tape motor. Its output switches Q808 to send a pulse to the control unit via its pin#2. Check the voltage at the collector of Q808 and look for the pulsing as the motor runs. The Hall effect IC detects the N-S-N-S...
  12. kellys_eye

    Vintage Sharp RT-3388a digital tape counter not counting

    Presumably the tape is actually running when the counter isn't clocking?? If this is the case then check the sensor(s) that will be coupled to the tape motor drive mechanism. Quite likely they are optical (dirty) but may eve be mechanical (again, dirty contacts). Post a link to the schematic...
  13. kellys_eye

    Transformerless audio amplifier

    What sort of power output? Direct mains powered? Absolutely not. As above, the safety issue is critical here. Discrete components or integrated? You seem to indicate discrete (for some reason). There are kits and ready-made units that foot the bill (a few £) but none 'mains powered'.
  14. kellys_eye

    Solar garden lamp repair

    The panel should produce a voltage proportional to the amount of light falling on it i.e. you should be able to see it changing if you cover/uncover the solar cell. Some of the 'exceedingly cheap' solar lamps might not even have a solar panel at all - a charged battery could keep the light...
  15. kellys_eye

    What is the equivalent to this Triac T16C8 ?

    Amperage and voltage - in this case 16A and 800V. Yours may be a 'logic level' triac i.e. is designed to be triggered at logic level voltages. Most component suppliers will have a parametric search list of triacs where you can put the relevant specifications in to narrow down the search...
  16. kellys_eye

    What is this? Driving me nuts

    Being a passive component it is not likely to be the cause of the fault - just the result of it...... Something else in the circuit has gone wrong.
  17. kellys_eye

    Ramsey RF kits

    Is it just me and my browser but all the files have NO schematics - plenty of board layouts but the schematics don't show (blank pages)?
  18. kellys_eye

    Help needed

    Is this 0.4V a 'supply' or a signal? If it's a supply then forget it. If it's a signal then apply it to a non-inverting op-amp arrangement with the appropriate gain (x12.5 to x30 variable).
  19. kellys_eye

    Help needed

    The forum considers all information to be of potential benefit to other users than just the OP and usually ask that the issue is discussed openly. Fire away!
  20. kellys_eye

    Circuit protection

    Fuses don't protect circuits. They protect the feed cable(s).
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