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  1. dorke

    VCI module

    It is a capacitor(Tantalum 10uF/35V) marked as C258 the same as it's neighbor C261. First thing to do is replace it and hope for good-the area around it looks badly burned. The green wires look like a manufacture's bug-fix,nothing special.
  2. dorke

    Simple power supply?

    If you post the design,we can review it. That may be helpful before you actually start.
  3. dorke

    transistor in saturation mode

    Let me start by saying you can not compare apples to oranges. The graphs are of the output characteristics(I -V curve) in C.E VCE vs. IC in C.B VCB vs IC The input is different as well iB vs iE For further understanding look here: I think you will like the content as well as the accent ;)...
  4. dorke

    Testing a NPN Darlington Transistor

    Your welcome,it's our pleasure :)
  5. dorke

    Simple power supply?

    The other side of the LM350 limit is Vi-Vo>3V. So if you have another LM350 use them in series to do this: Use the 12V of the transformer! 12VAC -->retifier+filter cap-->LM350T output set to about at 11V-->LM350T output set to 6V. important:; use a full rectifier ( bridge or dual diode) not...
  6. dorke

    What component to use to keep multiple pins high

    Here is another very interesting IC for such applications: the TI TPL9201 It adds a 5V LDO regulator with power on reset signal on board. and AC-line zero crossing detection. Only needs to make coffee to be perfect :cool:
  7. dorke

    Simple power supply?

    Mike, The thing you do wrong is running the LM350 at a Vi-Vo > 10Volts. In this case the current limit is no longer guaranteed to be 3A . There is a de-rating factor ,only 0.25A is guaranteed (for vi-vo=30v). see here: from LM350 data sheet If you only need a "fixed 7Volts output"...
  8. dorke

    variable power supply parts problem

    May I add that the input fuse value is too high, a 1A is enough. Are you going to build this PS or is it just a theoretical drill? Assuming a 20Vac transformer: "full current=1.5A" is only possible for Vo>13V(about). For Vo <13V, due to power dissipation limits of the regulator only 0.15A is...
  9. dorke

    Testing a NPN Darlington Transistor

    ModemHead, You are correct ,there is no C-E measurement! I jumped to the conclusion(Freudian?) that the "infinity" was of E-C :oops:. ADRT, can you please test the E-C bidirectionally and post?
  10. dorke

    Testing a NPN Darlington Transistor

    ADRT, good find,but... In this case your original darlington can actually be good. Best thing would be to build a simple test circuit for it . like this: closing the switch should light the led(a 20ma led) . Voltages on the darlington should be about: VCE=0.9V VBE=1.4V
  11. dorke

    Testing a NPN Darlington Transistor

    Since your measurements revile there is no C-E reverse diode. A better equivalent replacement should be this one : ST901T
  12. dorke

    Testing a NPN Darlington Transistor

    Unless... It is not a "pure Darlington".i.e has internal B-E resistors ,TIP120 like.
  13. dorke

    Testing a NPN Darlington Transistor

    Yes. The Darlington is defective.
  14. dorke

    Add a resistor to invert a sine wave??

    A picture worth 1000 words... The current in the loop is i. Voltages on the resistors are: VR1=i*R1 VR2=i*R2 VR3=i*R3 Voltages on the measurement points (vs.GND )are: Vn1= VR2 = i*R2 Vn2= -VR3= -i*R3 It is not that "the signal is inverted", It is just the way you measure and what is your...
  15. dorke

    Bose amplus 100 amplifier weird noises

    What is feeding the input of the AMP? It should be a differential signal with shild(+,-,GND). Can you try and see if there is distortion on the line-outputs(differential as well)?
  16. dorke

    Bose amplus 100 amplifier weird noises

    You can find a lot of helpful info in the installation guide, including block diagrams and more. http://pro.bose.com/pdf/pro/archives/amplus50/og_amplus50_eng.pdf BTW, Is the distortion present on both channels (in 2 channel stereo mode)? Does the volume controls have any effect on the distortion?
  17. dorke

    Bose amplus 100 amplifier weird noises

    How does the AMP sound in low output volume? What was the "no power" problem you found?
  18. dorke

    Help with air hockey digital scoreboard

    What is feeding power to the board?What voltage? Is there a Power Supply? Try touching the parts on the board,Any parts are warm or getting hot? Have you got a DMM? If so measure the voltage on DZ and U02(2 pins). Don't know how to load video here,you can load on youtube or such and post the...
  19. dorke

    Help with air hockey digital scoreboard

    Can you describe the "flicker"?at what rate? Is the display readable when it flickers? Doe it count correctly before it stars "flickering" ? On one display board(the one without the LEDs) there are signs of something spilled. It needs cleaning with rubbing alcohol and a cotton swab- especially...
  20. dorke

    Help with air hockey digital scoreboard

    Please start with brand and model. Schematics and/or service manual may help a lot. Take some closeup photos as well and upload them.
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