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  1. dorke

    Bose amplus 100 amplifier weird noises

    It looks like some replies are missing from the discussion... Please remind me ,what are you finally using for the "speaker scope"? In any case, it will be loading the circuit under test . If you use it for testing low impedance circuits it may be o.k, but for hiZ circuits it isn't. If I...
  2. dorke

    Is it my transformer or rectifier?

    I tried to find info on that unit on the web,nothing showed up. What kind of PA is it? Do you have any service manual or schematics? The 25A CB on the unit hints at something consuming about 1KW of power. Under normal conditions a 20A CB on the wall shouldn't trip, although it is obviously a...
  3. dorke

    Is it my transformer or rectifier?

    Boy oh Boy, This all debugging process is so not methodical ! Why complicate things when they can be simple? Can you please answer some simple questions: 1.What is the Make and Model of the AMP? 2.What is the value of the mains fuse on the unit value? 3."trip the circuit breaker", Does the...
  4. dorke

    Need help repair dead switching power supply

    The 16 pin IC KA7500B is a Fairchild SMPS controller
  5. dorke

    Is it my transformer or rectifier?

    On a transformer like you have(step down) , the resistance of the primary would be higher than the secondary. The resistance would be small ,can be a few ohms . The meter it will beep.
  6. dorke

    Is it my transformer or rectifier?

    BTW, The 0.6ohm secondary you measured sounds normal for a transformer that size. what is the units fuse value?
  7. dorke

    Is it my transformer or rectifier?

    What is the Make and Model of the AMP?
  8. dorke

    footstep power generator

    Oh well, I guess Zimbabwe has some more serious problems than electricity... Human generators is not the way to go, unless it is for a school project or "fun". Seriously, Water,Sun or Wind :clean and plenty energy to harvest.:cool:
  9. dorke

    Is it my transformer or rectifier?

    The failure process if you apply 220V instead of 110V would be the following. In general the "weakest links" are damaged first: 1.Momentarily the power supply DC unregulated voltages will all double. that can instantaneously damage all the semiconductor devices in the unit (those that...
  10. dorke

    footstep power generator

    What jumps to mind is a piezo in the boots...
  11. dorke

    NEED HELP!! Cant find this little part

    Just to clarify, the above link is just for showing where the Logo came from ......
  12. dorke

    NEED HELP!! Cant find this little part

    A picture worth a thousand words: The site is no longer active=it is part of Diode now
  13. dorke

    identify transistor

    Well, It can be Si2399DS ,a P-ch MosFET( code O1). Full marking here ,
  14. dorke

    NEED HELP!! Cant find this little part

    Edd, No way,100% it is not a Transzorb(all of them have only 2 pins - look at page 16) !!! Adam, don't try what Edd suggested! If you do, you may end up with a burnt IC ...
  15. dorke

    Sony str-k502p receiver

    No problems with opening that connector,lift the tab with your finger. run ha? because of that terrible movie ? ...a great tune though
  16. dorke

    NEED HELP!! Cant find this little part

    Adam, I think Martin nailed the company name. The Logo looks like that of BCD-semiconductor. The company was acquired by Diodes- 2012. You may try inquiring at Diode , if it is indeed their part marking they will identify it for you.
  17. dorke

    SOT-23 NMOS transistor power dissipation question

    You didn't say how many solenoids you need to drive. Take a look at the 7 drivers in a pack the TPL7407L it may save you a lot of space.
  18. dorke

    Solving boolean algebra task - HELP

    Apart from the usual table method etc. You can solve it "verbally" : conditions 1 to 4: "Key" AND "Driver" AND "driver-Tied" AND "pass-empty" condition 5: "pass-full" AND "pass-tied" If at least one of the above 2 sentences is satisfied the total condition is satisfied. That means "OR"...
  19. dorke

    Simple power supply?

    eetech, Mike only has a 12V transformer. A simple thing would be to use a higher filter cap for the first LM350. The 4700uf value is somewhat marginal(theoretically) but will do, adding 1000uF or more will clear the case.
  20. dorke

    Simple power supply?

    eetech, Now that is much better!... still think it will not work.;) I wonder what are the exact conditions of the simulation. For instance, can you make it simulate different temperatures,350 device variances,R and C accuracy etc. purpose being worse case scenario design
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