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  1. WHONOES

    Resistor to discharge capacitor

    I always put a bleed resistor across any large power supply Cap's so that they discharge after 20 seconds or so. Discharge rate depends on the size of the cap and value of resistor.
  2. WHONOES

    Diy generator

    Further to DAVE9's comments, a Stirling cycle motor might be worth considering. It is sort of a combustion device but can be run on waste energy (heat). I did think some years ago about adding a device that collected the waste heat from my heating system to collect useful energy using a Stirling...
  3. WHONOES

    Stage Line 500W amp repair project

    Just noticed that there is a part missing from the board at PR1. It's used to adjust the quiescent current in the O/P transistors and is quite important. Did you remove it?
  4. WHONOES

    Stage Line 500W amp repair project

    Have you checked voltages on Q1 and Q22 as suggested. If so, what are the results.
  5. WHONOES

    Stage Line 500W amp repair project

    If you are referring to Q1 and Q10 then NO they should not have 64V on them, they should be close to 0V. They will be turned hard on and so will the rest of that half of the O/P stage. What voltage do you have on the bases of Q11 and Q22? Before you make any further checks, I would suggest...
  6. WHONOES

    LC parallel tank circuit

    Must confess, I don't know what the circuit is for.
  7. WHONOES

    Resistor to discharge capacitor

    Try a 100W incandescent lamp. It will also give you an indication of state of charge.
  8. WHONOES

    Diy generator

    If you go down the windmill route, you could have a bean eating contest before hand as a possible source of free energy!!
  9. WHONOES

    Stage Line 500W amp repair project

    Which transistors are you referring to in post #409?
  10. WHONOES

    Harman Kardon SB 16 Subwoofer Low Volume

    Sounds as if the speaker coil could be off centre which would make it sound a bit scratchy. If so, then that's the end of that. You can check by taking the speaker grille of and gently push on the voice coil. It will be apparent if it is off centre.
  11. WHONOES

    Harman Kardon SB 16 Subwoofer Low Volume

    Have you got the Trim Switch in the correct position? See page 4 of the manual.
  12. WHONOES

    Stage Line 500W amp repair project

    The supply voltages seem a bit high but I guess as they are off load they are not unreasonable but it does suggest that transformer regulation is not very good. If you haven't removed Q10 yet, you could try soldering a100Ω resistor between the bases of Q1 and Q22. Then connect a DMM switched to...
  13. WHONOES

    LC parallel tank circuit

    The simple way to check the resonant frequency of your L/C circuit is to disconnect it from the transistor circuit. Connect a 1K resistor to one end of it so that they are in series and then connect a sine wave signal generator across the resultant circuit. Connect an oscilloscope across the L/C...
  14. WHONOES

    Few questions about usage of TI BQ2054

    Schottky diodes are no more likely to fail than conventional silicon diodes UNLESS you exceed their reverse voltage rating. This applies to all types of diode and for that matter all semiconductors.
  15. WHONOES

    Few questions about usage of TI BQ2054

    No. Your schematics are very difficult to read because of the shading you have added.
  16. WHONOES

    Computer speakers power issue

    No It's not dust. looks as though something has leaked into the enclosure. Were they second hand or pre owned as the term is these days.
  17. WHONOES

    Computer speakers power issue

    What has been in the corner of the enclosure where all the crud is? Has the box been standing in something?
  18. WHONOES

    Stage Line 500W amp repair project

    You just need to remove any fuses between the amps and the supplies and then measure them with a DMM to see if they are in range. ± a volt or two is OK. Any substantial deviation might indicate a PSU issue but I think that is unlikely.
  19. WHONOES

    Computer speakers power issue

    As for the alcohol. Try some undiluted screen wash additive for the car. It is usually Ethanol or IPA or sometimes a combination of the two. It's cheap and it works. Another source in an aerosol is de-icer which is very similar to screen wash.
  20. WHONOES

    Computer speakers power issue

    The crud in your pictures looks a bit like battery leakage. Have there ever been batteries in your speakers? Or perhaps a capacitor has leaked.
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