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  1. kellys_eye

    RF balancing (50 ohm traces, baluns etc...)

    As with any tuned circuit the output stage (filter) has to be tuned correctly and component tolerances can make a difference. Ideally you would monitor the input and output signals and tune the circuit for maximum pass (resonance) and, better still, use a sweep generator to produce a 'live'...
  2. kellys_eye

    What's this called (knob attachment)

    That's an insert for a 'collet knob' (with securing nut, of course). Typically found on high-end test equipment. I have a small selection recovered from dismantled equipment - decent knobs are hard to find these days - giggidy.
  3. kellys_eye

    Not sure to be safe or sorry

    Paralleling LEDs on one resistor is a bad idea unless they are closely matched in value as any difference in individual devices will cause current to flow unequally, lighting one brighter than the others and quickly causing it to expire. You can wire a few in series and use a suitable current...
  4. kellys_eye

    Help with varistor

    Googling the device code comes up with this: http://www.spiratronics.com/data/6815.pdf which tells you everything you need to know about that particular varistor and the range it comes from. You can then use the information to find a similar device from other manufacturers. Visit the Digikey...
  5. kellys_eye

    RF balancing (50 ohm traces, baluns etc...)

    Schematic? Layout? What frequency are you talking about? I'm presuming 800+MHz where circuit board traces become important and tracks can act as inductance/capacitance etc therefore need to be taken into account for correct power transfer....
  6. kellys_eye

    Sony MegaWatchman FD-500

    eBay is one path to take (obviously) but your success can vary enormously depending on how and when you advertise it. There are some 'antique' (or retro) equipment forums that could advise better on potential pricing but don't expect miracles - non-branded devices of this sort often sell for...
  7. kellys_eye

    Sony MegaWatchman FD-500

    There's still a good market in retro equipment and Sony are a good enough make to keep interest and prices high if you want to sell it on.
  8. kellys_eye

    Prob with Yamaha S250 digital keyboard

    Something loose/broken inside most likely. Check connections to the keypad that selects the sounds and look also for cracks in the circuit board and dirt under the keys of the sound selection keys.
  9. kellys_eye

    Sony MegaWatchman FD-500

    Dream on. $75 minimum. Point is, do you still have terrestrial TV signals in your area any more? Most countries have (or are) changing to DIGITAL signals that those old TVs won't receive anyway.
  10. kellys_eye

    Challenges trying to reach 300 baud BBS with my acoustic coupler modem

    ISTR they were notoriously poor for interference from external noises events - even picking up knocks and vibrations despite the cushioning. Place the whole thing on a foam pad and move anything that can remotely create noise away from the area.
  11. kellys_eye

    What is this SMD component?

    I had a notion that the active device was a three terminal regulator - given the component distribution around it - and with the expanded view as the presence of the bias potentiometer this would seem to increase the likelihood. The 'bar' on the package does lead one to believe it has some...
  12. kellys_eye

    Forum Categories and Improvements

    Never heard of Xenforo before but I can say that the layout and format of the site is one of (if not THE) cleanest and most user friendly that I've come across. Moderator attention is also nicely done and subtle with it. I've not been here long but I can't see anything I'd like to change -...
  13. kellys_eye

    Power supply series connection

    If one PSU is lower amperage then the total MAXIMUM amperage will be equal to the lowest supply value. In your example you could get the 31V at 1A maximum. Diodes are usually specified when you parallel PSUs - in which case the total amperage is additive (i.e. the sum of all the PSU amperage...
  14. kellys_eye

    Trying to fix broken backlight on a Soniq E55V13A TV

    LED back lighting tends to have very specific and sensitive shut down circuitry attached. Shorted LEDs, open-circuit LEDs, over current etc etc any of which may cause a shut down situation. LEDs are also very thermally sensitive (in terms of failure) therefore can cause problems at unspecified...
  15. kellys_eye

    Error in Phase lock loop using ic 4046

    Time constant of the low pass filter.
  16. kellys_eye

    What is this SMD component?

    There does seem to be a 'bar' marking on the device indicating a polarity - hence the 'diode' assumption but a quick test with a multimeter should tell.
  17. kellys_eye

    Circuit schematic

    Inevitably based on a matrix arrangement - like most (all?) keyboards. Maybe even a standard format/interface device. Never seen a 'mechanical' hack of this keyboard but there are examples of the coding being hacked.
  18. kellys_eye

    TP4056-42 Without battery temperature sensor

    Always follow the datasheet.
  19. kellys_eye

    What is this SMD component?

    It's a little green rectangular thing...... ( @Alec_t the marking is a 'D' ) Have you measured it? Diode perhaps? Maybe an inductor.
  20. kellys_eye

    How To Make A IP Camera Tester?

    Is it a POE device or powered independently?
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