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  1. KrisBlueNZ

    2M+ ohm resistors not resisting

    You need to turn the power supply OFF. Disconnect everything from the trimpot position, then measure RESISTANCE, not VOLTAGE, of those two resistors. Actually, just measure the one closest to the trimpot. Your analogue multimeter could damage the IC if you measure the other one.
  2. KrisBlueNZ

    2M+ ohm resistors not resisting

    Here's the long explanation for all of this. Please Google any terms you're not familiar with. The regulator circuit is controlled by the controller chip, the 8-pin SOIC (small-outline IC) that may be a UC3843 "current-mode controller". This chip generates an ON/OFF control signal to the big...
  3. KrisBlueNZ

    audio amplifier with unstable output offset voltage

    You're welcome. I hope it gives you many more years of good quality sound and reliable operation. LOL!
  4. KrisBlueNZ

    Denser than Osmium

    LOL! You're right about the warning flags. The thing is, I can handle it when the poster doesn't know much about electronics... what gets me is when they won't follow simple instructions, and when they just IGNORE my questions. I ask questions because the answers are important, and when they...
  5. KrisBlueNZ

    2M+ ohm resistors not resisting

    OK, here's what I suggest. Disconnect everything from the trimpot position, so there's nothing connected to those three holes at all. Now measure the resistance of the resistor closest to the trimpot. This will give you a correct reading, because (as far as I can see), there is now nothing...
  6. KrisBlueNZ

    2M+ ohm resistors not resisting

    To the OP. I'm going to sleep now. I'm sure KJ6EAD or CocaCola or someone else can tell you what to do. Perhaps you don't want to talk to me anyway. You need to reduce the resistance in series with the trimpot and/or increase the resistance from the voltage feedback pin (pin 2) to ground...
  7. KrisBlueNZ

    audio amplifier with unstable output offset voltage

    Are you sure you have the pinout right? It looks like the two versions of the KT315 have different pinouts - the flat one is b-c-e and the TO-92 one (cylindrical with a flat section) is e-b-c, according to the diagram I linked to in post #11. I wouldn't bother replacing VT1 anyway. You already...
  8. KrisBlueNZ

    2M+ ohm resistors not resisting

    CC, thanks for those... I can't really be sure of the connections to those component positions though. The overlay gets in the way too much. Also, I can't read the resistor values. But I did notice that the controller in that photo is a UC2843. The OP said his was an 8848; maybe it's a 3843 and...
  9. KrisBlueNZ

    2M+ ohm resistors not resisting

    Thanks, I'd already recognised that from the pin connections. He said it's a UC8848A, which I can't find anywhere. There IS a 3848, but it has 16 pins. Maybe the 8848 is a third-party 8-pin version of the 3848 with the same pinout as the 3842/3/4/5. Yes, I saw that. Somehow I got the idea that...
  10. KrisBlueNZ

    2M+ ohm resistors not resisting

    You put a 56K resistor "at the output terminal"? I don't know what you mean. And I appreciate you trying to advise me on how to communicate, but I have some advice for you. If you don't know what someone means, SAY SO. Don't just ignore questions. Especially, don't ignore the same question...
  11. KrisBlueNZ

    Denser than Osmium

    For your amusement. The most frustrating discussion I've had on electronics point so far. www.electronicspoint.com/2m-ohm-resistors-not-resisting-t255069.html We're up to post #25 so far, and I've established two useful pieces of information.
  12. KrisBlueNZ

    2M+ ohm resistors not resisting

    OK. Well, you'll need to wait until there's sunlight then. The area I need to see clearly is the row of component positions (most of them are empty) that is above and to the right of the green box you drew on the fourth drawing. I need to be able to make out every track and connection in that...
  13. KrisBlueNZ

    2M+ ohm resistors not resisting

    ... and... WHAT IS THE RESISTANCE MARKING (NOT THE "3296", THE OTHER NUMBER) ON THE TRIMPOT?
  14. KrisBlueNZ

    2M+ ohm resistors not resisting

    OMG. LISTEN. I NEED TO SEE A CLOSE-UP PHOTO OF THE AREA FROM THE CONTROLLER CHIP TO THE TRIMPOT PINS.
  15. KrisBlueNZ

    2M+ ohm resistors not resisting

    I said "8-pin controller IC". Eight pins.
  16. KrisBlueNZ

    How to make a fan unit RF dmx controllable

    Ah, thank you Dave :-)
  17. KrisBlueNZ

    2M+ ohm resistors not resisting

    I can't read any numbers on the controller IC. I cannot tell where the tracks go in the area between the trimpot and the controller IC. You may be able to measure those tracks with a continuity tester but this will take a lot of time and so far you haven't shown much inclination to read my...
  18. KrisBlueNZ

    2M+ ohm resistors not resisting

    OK LISTEN. Changing the resistance of the trimpot WON'T WORK. You are going to have to change one of the resistors on the PCB. I can tell you WHICH resistor you need to change, and what value to change it to. BUT I need to see a close-up of the tracks in the area that includes the trimpot...
  19. KrisBlueNZ

    2M+ ohm resistors not resisting

    That looks exactly like the ebay picture. I need to see a picture that shows the trackwork clearly. It needs to be zoomed more closely around the area that includes the trimpot pins and the controller chip (the 8-pin one).
  20. KrisBlueNZ

    2M+ ohm resistors not resisting

    The "3296" is the name of a RANGE of trimpots. Bourns manufactures trimpots in that range with values up to 2M, but that doesn't mean that the trimpot on YOUR board goes up to 2M. Most likely it's a lot lower than that. Look for a three-digit number like 103 or 203 that will tell you the...
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