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  1. kellys_eye

    Carbon film resistor?

    I don't recommend replacing that part AT ALL. It's blown for a reason - not a GOOD reason either - and replacement will either re-create the original fault or cause something else, potentially more damaging, to occur. Given the safety precautions usually advised with electric blankets you'd be...
  2. kellys_eye

    Help me understand a 12V SLA charging circuit.

    Check your eyesight. My quote said 22Ω <----- that's the symbol for OHMS, not a zero. Wow! The datasheet shows that the relays are AVAILABLE with coil voltages ranging from 3 to 60V and that the one on the board you have is coded as having a 9V coil. Similarly the relay coil (for the 9V...
  3. kellys_eye

    Help me understand a 12V SLA charging circuit.

    The relay and resistor don't carry ANY of the motors current - the only current flowing is that dissipated by the relay coil (and the series resistor) when Q4 is saturated. The circuit board you posted an image of clearly shows a 22Ω resistor and it doesn't look to be burned out - ever wondered...
  4. kellys_eye

    Op-amp circuit of an electronic card for a turbine flow meter (m3 Counter)

    Yes there is. The components at the bottom of the (poorly drawn) schematic are effectively across the op-amp inputs and there is a connection to Vcc through R5
  5. kellys_eye

    Help me understand a 12V SLA charging circuit.

    Whilst we are fully prepared to assist with your questions you must appreciate that we can't be expected to do the work FOR you. Yes, I could reverse-engineer the board completely and draught a schematic in conventional form but what does it do for ME? Other than take me hours of my time...
  6. kellys_eye

    PWM generator

    From the link you provide I see no reason or requirement for the need to adjust data low/high. Frequency and duty cycle, yes. At a fixed 12V (with optionally a 5V output) will be enough. There are many such schematics with the appropriate component calculations available from a simple Google...
  7. kellys_eye

    Yorkville 100watt Mixer/Amp - Replaced Transistors

    Further in-depth testing would best be done with a test tone and oscilloscope. Tracing the signal through from input to output at the appropriate levels (low to high) will soon reveal the point of distortion. It is possible to get an oscilloscope function through the input of a soundcard (PC)...
  8. kellys_eye

    Old Magnavox Console Repair

    Meet (or exceed) the basic specifications for: Vce Ic Ptot Hfe and the physical case size/shape/pinout and you'll probably ok with anything that matches. Go to the larger component sites like Digikey, Farnell, RS Components etc and use their parametric search options to select those 'basic...
  9. kellys_eye

    Mechanical noise DC brush motor

    There's inevitable noise from the commutator that you can't do a lot about though.
  10. kellys_eye

    Help me understand a 12V SLA charging circuit.

    Still not right. R18 goes in series with D4. There is no connection from D4 to the base of Q4. The 22 ohm (R18) is the correct value and simply limits the current in the relay coil. Although your schematic is 'close' it's not close enough - small errors make huge differences. Getting the...
  11. kellys_eye

    Help me understand a 12V SLA charging circuit.

    Not a problem. Reverse-engineering a circuit board is never straight forward however if you get it right then the operation and explanation for the circuit operation becomes relatively straight forward. Sorry, can't help with the simulation software issue - never use them.
  12. kellys_eye

    Pressure sensor for focus pads

    Depends on the punch bag. If it is 'sealed' you could plumb in a simple connection to take the air pressure to a sensor - well, even if it's NOT sealed, it's still possible as you can calibrate for the 'leakage' effect anyway. Pressure sensors are readily available but consider getting hold of...
  13. kellys_eye

    Identify SMD inductor help

    The inductor seems to be part of a small SMPS circuit to develop alternative voltages within the device. They only 'burn out' if the switching device itself is shorted so you need to check for either a switching IC or a dedicated switching MOSFET that has gone short (or the reason for it going...
  14. kellys_eye

    Help me understand a 12V SLA charging circuit.

    Unclear from the schematic as drawn but if this is what you say it is....... The position(s) of the resistors are not as per the schematic. R18 connects from Sout2 to the cathode of D4 (to begin with) - there are other errors.
  15. kellys_eye

    Help me understand a 12V SLA charging circuit.

    There's no supply for the relay. The diode across the relay is reversed. R15/16/18 are just....wrong...... and that's just for starters.
  16. kellys_eye

    Help me understand a 12V SLA charging circuit.

    There is so much wrong with that schematic I don't know where to start! Perhaps 'you' could start by posting the schematic 'as is' instead of with those distracting moving dots?
  17. kellys_eye

    DVR 620 Ejects tape and powers off

    Repair it.
  18. kellys_eye

    GE Classic Radio Player 7-4135 schematic and amp question.

    so an upgraded power supply and new more powerful speaker too?
  19. kellys_eye

    GE Classic Radio Player 7-4135 schematic and amp question.

    Most modifications of this type involve installing a Bluetooth receiver......
  20. kellys_eye

    Grid of tiny-linear-actuators

    If the pins pushed against a flexible membrane and were spaced according to the flexibility then you'd get a pretty decent rendition.
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