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  1. KrisBlueNZ

    Opps, solder joins 2 traces. Now what?

    Really good advice here. I also find solder wick is very good for tricky jobs. For cutting stuff on PCBs I use a very sharp scalpel, and I hold it near the point and push my hand down firmly on the board so I have accurate control. Like when a dentist rests his hand on your jaw as he's using a...
  2. KrisBlueNZ

    capacitor polarity in a phono stage project

    I agree Steve. This is some of the worst audiophile wank I've ever read. I was tempted to ask him for reports from the double blind testing sessions he's done to confirm that it's not just all in his head. I'm subscribed to a couple of Yahoo groups for old English "hi-fi" toob amplifiers - Leak...
  3. KrisBlueNZ

    Astable multivibrator calculations and Multisim

    He's comparing calculated values with a Multisim simulation.
  4. KrisBlueNZ

    New alternator to car cause relay to buzz - can you help?

    It looks like both of those white wires connect to the same screw. If so, that would be the output of the alternator. So that would be the point to short to chassis. Otherwise, I don't know. Obviously, don't try to start the engine with the alternator shorted out! Just turn the ignition ON and...
  5. KrisBlueNZ

    TDA2030 VS. LM383

    No problem :-)
  6. KrisBlueNZ

    Split Rail Power Supply

    Good questions. 1. All resistors should be 0.5 watt metal film, 5% tolerance or better (metal film resistors are normally 1% anyway), except for the two 0.33 ohm resistors, which should be 5 watt wirewound 5%. 2,3. No, the recommended way to adjust the quiescent current (measured as the...
  7. KrisBlueNZ

    Circuit rectification help

    OK, the problem that Steve identified is that the inputs of the logic gate will float when the corresponding switch is open. When the switch is closed, the input is pulled up to VCC, which is good. But when it's open, the input isn't connected to anything. With most logic families, it will pick...
  8. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    Yes Adam, he is sampling two analogue inputs via the 10-bit ADC, conditionally scaling them if three digital inputs are all high, then outputting them to the two PWM generators, to produce waveforms with an average voltage between 0V and 5V, which are heavily filtered and buffered. I can't...
  9. KrisBlueNZ

    Astable multivibrator calculations and Multisim

    I assume this is a 555 circuit, right? I would expect the TH calculation to match very closely. The error you're seeing is about 3% which is more than I would expect. The TL calculation may not match exactly because the 555's discharge output is a transistor collector, which doesn't pull all...
  10. KrisBlueNZ

    Please, check for possible mistakes

    Well spotted to you :-) There's no telling what else the reference voltage is used for inside the chip. If it's being dragged down externally, that could prevent it from working. If it's not being dragged down externally, there's internal damage, and probably to more than just the reference.
  11. KrisBlueNZ

    Please, check for possible mistakes

    I don't think you've answered the question of why pin 7 measures 23V when the specified supply voltage for the circuit is 9~15V. Also, pin 8 is the reference voltage output from the UC3843; it should be 5.0V.
  12. KrisBlueNZ

    Transmitt ASCII data

    I think kpatz is onto something. If the baud rate of your receiving UART is a bit too low, it will sample at the wrong point in each bit; the error will increase as the bits arrive. When the last bit arrives, the sampling times are so far off that the bit 7 sample is actually taken at the...
  13. KrisBlueNZ

    New alternator to car cause relay to buzz - can you help?

    Hi Wilf and welcome to Electronics Point :-) I don't know much about automotive electrical but I'll try to help. My first thought is that the voltage comparing relay is buzzing because it's rapidly alternating (no pun intended) between two states: first, it thinks that the alternator's output...
  14. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    Re your code in post #19, there is an obvious problem: the while(1) is inside the loop! I don't think that's valid C code; a do without a corresponding while() isn't valid syntax. I would approach this problem using some debug code to output diagnostic information from the serial port. To start...
  15. KrisBlueNZ

    do you know these resistors?

    No. The voltage at V+ is around 50V maximum. A 63V rated cap is fine. That all sounds right and makes sense except for the Ic and Ib figures. But don't worry about that. The LB suffix devices have a minimum current gain of 240, so you should use those if possible. Did you replace C4? (That's...
  16. KrisBlueNZ

    NiMH solar battery charger

    I'm afraid there are some problems with this approach because of the electrical characteristics of the solar panels. An array of solar panels is a voltage source; the amount of voltage it generates depends mainly on two factors: the amount of sunlight, and the amount of current that's being...
  17. KrisBlueNZ

    D-flipflop freq divider

    I may be missing something here, but I don't think that discrete gate circuit is a D flip-flop; I think it's a transparent latch. D flip-flops are edge-triggered, so the D input is just sampled at the instant when the clock goes high. While clock is high, changes on D won't have any effect on a...
  18. KrisBlueNZ

    Power supply help

    This is way outside my experience, so this is just a suggestion. One, two, or even three, biiiiig chokes in pi filter configurations, with relatively low smoothing capacitance at the transformer end, increasing towards the load end. For example, 1000 µF on the bridge output, rated for a pretty...
  19. KrisBlueNZ

    Split Rail Power Supply

    Yep, you're spot on there.
  20. KrisBlueNZ

    need a "translator" for 12 VDC power supply project

    Good advice there from Fish. He is suggesting that you can limit the current to the anodising setup by connecting light bulbs in series with the circuit. Probably, headlight bulbs would be appropriate.(Edit: No, Fish has better ideas.) Each bulb needs its own switch, and you measure the current...
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