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  1. KrisBlueNZ

    Need help with a PSU schematic

    The shape of the ripple waveform is not very important. The regulator will deal with it pretty well. What's important is the power dissipated by the zener, and especially the worst case maximum power. The load current will affect the zener dissipation, but the main factor is the mains voltage...
  2. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    No. You've connected to the wrong pin. The wire link that goes to pin 2 of the IC should connect to the middle terminal of the LM336Z, which is identified as "+" or "K" or "cathode". The other connection to the LM336Z is right. No. The circuit should draw less than 20 mA from the battery. Even...
  3. KrisBlueNZ

    Soft start circuit

    I see. That's a clever idea!
  4. KrisBlueNZ

    Rewiring 7-band EQ

    Yes, you can power the buffer from the same 12V supply that you use for the graphic equaliser. The document you linked to is very nice, but it's for transistorised models. If you can find a Sams Photofact document for a toob model from the same era as yours, that could be very useful. Thanks...
  5. KrisBlueNZ

    Soft start circuit

    Here's a soft start circuit I designed yesterday. I wasn't going to post it, since it's not directly relevant to the OP's problem, but it might be of interest. It takes a +12V supply and drives a 1.5A load. I've just used a resistor here; I guess it would have been better to simulate it with...
  6. KrisBlueNZ

    Soft start circuit

    Steve, did you intend to put a capacitor from the base to the emitter?
  7. KrisBlueNZ

    Rewiring 7-band EQ

    Whether changes will be needed to the tone controls depends on how they're connected. Now that I know you want to keep them, I'll bear that in mind. Here's a design for a stereo audio signal buffer. It has an input impedance of 1 megohm, which is probably close to the resistance of the...
  8. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    Well, it's not just you that I don't want to give up on. I suggested a circuit, and I have reasonable confidence that it will work properly; I don't want to give up on THAT :-) That's a bit weird. Perhaps you should try using one of the batteries that you intend to use with the circuit when...
  9. KrisBlueNZ

    Need help with a PSU schematic

    Ah, yes. That caught me as well. When you place a sinewave signal generator, the "Amplitude[V]" field actually sets the peak voltage. Not the RMS voltage, which I would have expected, and not the peak-to-peak voltage, which is about as logical as the peak voltage. I regard this as a bug in...
  10. KrisBlueNZ

    Rewiring 7-band EQ

    OK, I understand about the tuner. There's the row of five controls, and the tuning pointer moves left and right against the panel above them. I can see the brackets for the light bulbs at each end for illumination. OK, so the treble control is at the end. OK, that might make things difficult...
  11. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    Sorry for the slow reply. I think we should try to get the three-colour circuit working. Can you try this procedure? 1. Disconnect R6. 2. Supply about 18V into the circuit. 3. Set your multimeter for voltage and connect the negative lead to the 0V rail where it enters the circuit (track 12 on...
  12. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    You an use the red-green circuit in post #42 without any changes. You might want to increase the LED series resistor from 1k to 1.5k to reduce the LED current. Also you could increase the resistor that feeds the LM336Z to 27k as we calculated earlier. I'm looking at your layout and description...
  13. KrisBlueNZ

    Buying stuff from China.

    That's another good reason to avoid these components. Imagine the health and safety risks to the salvage workers.
  14. KrisBlueNZ

    Voltage or Amplitude?

    Yes, VCC is the positive supply voltage. Your emitter resistor is too high. Start by choosing a quiescent collector current. For example, 1 mA. This current flows in the collector and emitter resistors. Actually the emitter resistor also sees the base current, but that is relatively small, so...
  15. KrisBlueNZ

    Need help with a PSU schematic

    OK, here are the calculations for minimum and maximum VOUT for the +15V rail. I haven't taken every possible factor into account; these are just to show you why the output voltage could be significantly different from the calculated value. Routadj = 200 ohms +/- 1%. Min = 198 ohms; max = 202...
  16. KrisBlueNZ

    Need help with a PSU schematic

    You're right that you should replace the bridge rectifiers with ones with a higher voltage rating. But no, the lower voltage rating will not cause the unexpectedly high DC voltages. As you say, the DC voltages, without load, are correct given that the transformer secondary voltages are 24.6V AC...
  17. KrisBlueNZ

    Reg:Switching regulator

    Have you tried the circuit on page 13 of the data sheet? http://www.onsemi.com/pub_link/Collateral/NCP3063-D.PDF
  18. KrisBlueNZ

    Need help with a PSU schematic

    If there's a problem with the voltage going too high when there's no load, you can connect a zener (with or without a series resistor) across the rail. Calculate the power dissipated; you may need a 3W or 5W zener and you may need to heatsink it. Just a suggestion.
  19. KrisBlueNZ

    Faulty Transformer/ Replacement reqd

    Hi loony and welcome to the Electronics Point forums :-) I had to reply, if just to say that your post is the model of how to ask a question on the forum. You've included the model number, the product description, your location, your mains voltage and frequency, several good clear photos, and...
  20. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    That layout looks good. Yes, natural light, without direct sunlight, is the best for taking photographs of circuit boards etc. Do you have a variable DC power supply? Open-circuit R6 and set R4 so the LED changes from green to red at the desired low voltage threshold - 18V I think. Then can...
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