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  1. S

    Rewiring christmaslights

    Sorry Little Spark - this is just not going to work. LEDs are not like filament lamps; they are current-driven DC semiconductors which have to be driven from a current-limited source (approximated in simple DC single-LED circuits by a series resistor to provide a relatively constant current of...
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    Rewiring christmaslights

    The four power transistors on the lowest part of the PC will provide the current source for each of the LED groups, driven in turn by the smaller transistors immediately behind the power transistors. These in turn will connect to the dedicated controller, which is not something that can be...
  3. S

    Rewiring christmaslights

    The first two answers given are almost certainly correct - the patterns are pre-programmed into the dedicated chip and can't be changed. The four driver transistors on the bottom end of the PCB will be driving LED groups on the output string, but the sequence is down to the embedded controller...
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    UK Advice on electrical quote

    As an experienced DIYer myself I agree with the pros here. I reckon actual labour charges are higher than you've allowed for and the time for the job is likely to be much more than you estimated. All in all, given the scope of the works I think you've had a very reasonable quote. On labour...
  5. S

    Broken lamp!

    https://www.electriciansforums.net/threads/polarity-of-e14-and-e27-lamp-holders.67893/
  6. S

    Broken lamp!

    The screw thread in the second photo tells us that the lamp takes Edison screw (E27) bulbs, in which case the live (brown) cable should be attached to the horizontal connector on the right of the middle photo, and the neutral (blue) cable to the vertical blade on the left. This is to make sure...
  7. S

    Smoke Alarms (Scotland)

    I'm not a sparky, just a former electronics engineer with C&G 16th edition regs pass from twelve years ago, so can't say about the trade side, but it is indeed true that the law in Scotland will require fully interlinked systems by Feb 2021. I've just finished installing mains powered and...
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    1960s power cable

    Good to know that the cable is indeed original and simply what was used. Back in 1976 I installed a stereo system made by Dynatron in a customer's home. It had a GL75 turntable in part of the system's very ornate wooden case, but I never saw the original wiring. There's a thread on the Lenco...
  9. S

    Battery drop battery voltage

    Dropping 10V at 25 Amps would be 250 Watts power dissipation - a lot of heat to cope with. The inefficiency of this approach will also exhaust your 12V battery - they are not designed for continuous current output of 25A (starting peaks are much higher but for short duration). I wonder how long...
  10. S

    1960s power cable

    I think that reverses how you should treat the live and neutral. The switch cable is connected in common with the incoming power cable on the right side, so this has to be the live feed as otherwise the switch would be breaking the neutral, which wouldn't make sense and would leave the motor...
  11. S

    1960s power cable

    Can't be certain, but it seems to be the most likely. It follows the red-black convention, with the right-most being the neutral in black (I assume). I guess the other figure of eight connection shown (connected to the leftmost terminal and the assumed neutral on the right) goes to an on-off...
  12. S

    1960s power cable

    The Goldring-Lenco GL75 is a vintage turntable dating back to the late 60s/early 70s. It could be supplied as a chassis for building into a bespoke stereo system, or fitted into a case and supplied complete with arm as a stand-alone turntable. The mains input wiring you show is not original, as...
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    Metal CU. Why?

    It is through the in-depth investigations conducted by fire investigation teams after major fires that causal patterns in what are still relatively rare fires are discovered. London Fire Brigade is the largest in the UK (Scottish Fire and Rescue the second-largest), and its fire investigation...
  14. S

    Metal CU. Why?

    Having recently retired from Scottish Fire and Rescue, could I correct some misimpressions? Firstly, all fire services in England, Scotland and Wales use a central system for recording incidents. The majority of fires start in the kitchen from human factors. Electrical fires are a much smaller...
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