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  1. F

    Guitar Aplifier

    I tryed circuit without speaker. Instead of a speaker, I connected 12V, 21W lamp. It was unable to read current drawing, becouse one moment was 13mA and in the other was 30mA..it was changing every half second or faster. Lamp was little flashing. What could explain that?
  2. F

    Guitar Aplifier

    Yes, please, post it.
  3. F

    Guitar Aplifier

    Any new suggestions? It seems that somewhere in circuit one component conduct too much current. Somewhere is mistake. But where? Why is current so high in fuse socket?
  4. F

    Guitar Aplifier

    What if DC supply voltage is too high? The secundary of my transformer is 24V, but when I messure voltage in fuse socket (without fuse connected), I read 31V. This is 7V higher. Is this becouse of the filter capacitor, or is supply voltage too high?
  5. F

    Guitar Aplifier

    I swiched circuit on and loudspeaker screamed, then I quick turned it of and on again and it shuted up so I could make messurements. Should I still account your advice, to replace Q4? I don't understand your explanation for VBE of Q5 and Q6. Why is that voltage so low? Can you explain in newbe...
  6. F

    Guitar Aplifier

    Ok, I messured voltages somehow...: VBE of Q4 (voltage accross R10) was 0.6V VBE of Q3 was 0.6V VBE of Q5 was 0.3V VBE of Q6 was 0.2V Author said, that I must check also voltage across Collector of Q5 and negative ground and across Emitter of Q5 and negative ground. Both voltages should be...
  7. F

    Guitar Aplifier

    How can I messure voltages, if when I put fuse in socket, speaker screams...? ???
  8. F

    Guitar Aplifier

    hm...very strange. I added 10kR potentiometer in series with R14 and turned it to maximum resistance. It doensn't make any difference..but why 470 ohms resistor in series with speaker makes difference??
  9. F

    Guitar Aplifier

    I really don't know what to do anymore. I checked everything and it's like in the original schematic. Why it doesn't work like it should? Resistors are right, especially R10 and R11 (I checked them hundreds of time). It is useable to change value of R14? Maybe it will work?
  10. F

    Guitar Aplifier

    In the original schematic it's drawn like ordinary resistor with fixed 2k2 resistance, right?
  11. F

    Guitar Aplifier

    That could explain differend current, through fuse, but not 10x higher, am I right? So I won't change nothing, even if I put r10 with 10k resistance in...I should check something else..but what? I checked every connection..If one of the transistors would be dead, amplifier wouldn't work at all...
  12. F

    Guitar Aplifier

    Author said, that I must change value of R10 to bigger one in small steps. When I get right one, it will be ok. I will add potentiometer to R10 and when I messure right current, I will get potentiometer out and messure it's resistance, and then I will know, how much resistance I must give to R10...
  13. F

    Guitar Aplifier

    I am sorry for my bad English. Yes, led is continuously lit. Resistor is connected like this: +---resistor---speaker----  - ...What if I change resistor R14 with bigger value and remove my resistor? Will then be better quality?
  14. F

    Guitar Aplifier

    I connected 470R resistor infront of a speaker and now I messure 25mA current. It is not perfect sound and it is not everything quite good, but Guitar works, when I connect it. I must seek for errors.
  15. F

    Guitar Aplifier

    Ok I replaced transistors and I tried circuit. When I REPLACE leads of avo-meter in fuse holder it mesures of about 100mA current. Speaker gives verry loud sound and when I remove leads of avo-meter, LED still flashes for few seconds. What can I check? It is this good behavier?
  16. F

    Guitar Aplifier

    I tested transistor Q5 out of circuit. I know, I can't test them inside of it. I will see. If amplifier will work and if one day woun't work anymore, I will simply rechange components that are now life shorted probably. PS.: Can you please check my PCB and tell me if it's good with original...
  17. F

    Guitar Aplifier

    C13 is good. I made a conuctivity test betwen + and -. It conducts for 1 second, then capacitor is unconductable for few seconds. I think, that Q5 is ok, becouse it conducts between collector and emmitor. It also show resistance between Base and Emitor of about 600 Ohms and in other direction is...
  18. F

    Guitar Aplifier

    Which components are in danger thoug?
  19. F

    Guitar Aplifier

    Can anyone just tell me please, how do I check NPN and PNP transistor with multimeter with range for testing diodes or with ohmmeter without any testing circout?
  20. F

    Guitar Aplifier

    Yes. I know that. I just didn't look good and now I understand it all. I have transformer with 24V secundary and I connected it's another secondary, so I got 48V. But I was wrong and now I will use original patent of this transformer. At least I know what was wrong now. As they say, we learn on...
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