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  1. kellys_eye

    Now I am going to ask 3 stupid questions, please dont laugh. but i cant seem to find info

    That variac will NOT deliver 12V at 50A - end of. The wire it is wound with has a maximum current rating and it is this that sets the maximum allowable current to be drawn. The variac rating is its absolute maximum. True, a 1.2kVA variac can deliver 10A @ 120V (1200W) but as the voltage...
  2. kellys_eye

    Macintosh SE30 CRT, dielectric grease and red 'paste'

    Simple silicon grease is all that is required. At a pinch you can even use 'Vaseline'.
  3. kellys_eye

    tip120 driving led array

    Indeed it is - quite common, up to the job too. Connect as per a transistor but add a resistor from gate to ground to help with switching off. As ever, always download the datasheet for the devices you are using. It will show you all the parameters and safe operating zones etc. There are...
  4. kellys_eye

    Now I am going to ask 3 stupid questions, please dont laugh. but i cant seem to find info

    Of course using a variac for any form of repair relies on the appropriate knowledge of how and why.... I'm aware of the lamp-limiter method for powering radios too - a variac/charger/rectifier is a bit 'brutal' for a speed control though ;) given the availability of cheap controllers nowadays...
  5. kellys_eye

    tip120 driving led array

    It boils down to the saturation voltage across the transistors e-c connections. BJTs aren't that good as switches in high-power applications so consider changing it for a MOSFET that can have an 'on' resistance of milli-ohms with a consequent dissipation of near-to-nothing.
  6. kellys_eye

    Non existent jack adapter

    Head East - a long way.....:D There will be a Chinese supplier that will do it but unless you're in the market for 100's or 1000's expect to pay a phenomenal price. You could do this with a small pcb, pcb-mounted sockets and a..... plug (somehow??). It would be 'open-framed' unless you...
  7. kellys_eye

    Now I am going to ask 3 stupid questions, please dont laugh. but i cant seem to find info

    10A is the maximum current the variac will allow without burning out - regardless of the voltage you set it to. But the current will depend on what's connected - NOT what the variac is set to. It's the connected load that determines the current that is drawn. But using a variac as a variable...
  8. kellys_eye

    Compatible replacements for "F" version (74F244N)?

    If you socket the device then popping in whatever version you can get is easy - no harm will come to the PC by using non-F versions but if you can get the 'proper' device then go for it.
  9. kellys_eye

    Need to replace capacitors in my Audio interface, a little advice please

    Sure they're 100uF? - it's normally power supply (rail regulation) capacitors that bulge and 100uF seems small to be suffering this kind of issue. Have you checked elsewhere in the equipment for similar issues? Look for low ESR capacitors having a 105C (temperature) rating. They are generally...
  10. kellys_eye

    Ceramic cased resistor

    Without the manufacturers marking (I'm guessing 'JM' is specific to the value and construction rather than its source) you can only refer to the OEM as found on the parts listing. But if you Google the 'key' part of my link (International Resistive) you will find a full spec sheet for the part -...
  11. kellys_eye

    Ceramic cased resistor

    Although marked as 3W a higher rated component of the same resistance will do the same job. Given your location you may be limited in choice but the following link is to a part from Farnell (a global supplier) that will be suitable...
  12. kellys_eye

    Compatible replacements for "F" version (74F244N)?

    The logic level transitions only become a particular issue if you're using the two difference devices on different supplies - if they are both run from a 5V rail and the logic levels are simply 0V and +5V then, for most circumstances, the use of CMOS in place of TTL won't become a problem...
  13. kellys_eye

    How could I convert/boost PWM frequency? 500Hz to 25kHz?

    Yes that digital pot would work.
  14. kellys_eye

    UTP CCA vs UTP CU cables

    Standard CAT5 cable will do - it's about the cheapest type of cable you can purchase these days anyway. I avoid CCA only for the potential soldering issues but if you crimp the connections then feel free to use it. Personally I'd use a two-core overall screened cable for a 20m run IF it was...
  15. kellys_eye

    Oscilloscope? ?

    'Dave' of EEVBLOG fame does some good tutorials on Youtube - worth a visit if you haven't already done so.
  16. kellys_eye

    Is a 3000 watt 12v to 120 inverter really just 2 1500 watt inverters ?

    I think dave9 was referring to the fact that the boat already has the winch (120VAC) so must have some source of supply to power it??? Are you looking to replace a duff one or to fit one that can power it if the boat didn't already have one? I'm surprised to see a 120VAC winch - even at 3000W...
  17. kellys_eye

    Static On My Radio

    You may have seen some power cables - especially to PC-type equipment - with 'fat lumps of plastic' attached to them. These are ferrite cores intended to help reduce the interference passing back to the mains supply lines. Putting a 'loop' of mains cable through a suitable core may make a...
  18. kellys_eye

    Recapping a PSU -choosing the right replacement caps

    Out of sheer nosiness :D what make/model PC (or motherboard) are you servicing? 30 years seems to point to a 386 or 486 (maybe Pentium)? Do you have an application for the PC or is this a nostalgia trip?
  19. kellys_eye

    Compatible replacements for "F" version (74F244N)?

    The 'AS' series is generally widely available and a better (i.e. faster) series than the 'F'. Unless you're mixing CMOS with TTL then there's usually no problem with swapping out for a 'faster' version (of course you can't do the reverse!).
  20. kellys_eye

    Hiya frae Edinburgh!

    Someone 'local' to me! You've chosen a very good hobby to entertain yourself. There are so many aspects to it that it's almost impossible to get bored! Enjoy yourself and don't be afraid to ask....
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