Is this normal?

Discussion in 'Amp Tech Center' started by charlie chitlin, May 30, 2019.

  1. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    I know...I know...but here goes...
    A couple of my amps, though otherwise totally fine, crackle quite a bit on start up.
    One is a Kendrick with very low hours.
    What is this?
     
  2. Bluego1

    Bluego1 Tele-Holic

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    Do you sometimes eat Rice Krispies when you play?
     
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  3. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    Only Cap'n Crunch.
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  4. elihu

    elihu Poster Extraordinaire

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    Dirty pots?

    I say this because I just ordered some De-oxit last night for one of mine that is doing the same thing.

    When an amp sits for awhile with no one turning 'em they can get that way.
     
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  5. robrob

    robrob Poster Extraordinaire Ad Free Member

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    A cracked solder joint can make crackling noise, then as it heats up and expands it makes good contact and the noise goes away. It can be very difficult to see these cracks but pushing on joints with a chopstick can help locate them.
     
    Last edited: May 31, 2019
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  6. peteb

    peteb Friend of Leo's

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    that's a great answer Rob.


    I could not answer that question, an amp crackle going away as the amp warms up, but your answer makes good sense.



    I just want to add the question of where does the circuit heat up and by how much. My DMM measures temperature, but I've never had a reason to use it.


    It would be interesting to measure the temp of the circuit at different places and see how hot it gets.





    based on what I know right now, I don't think it gets very hot, but it might not take much to affect the solder joints.
     
  7. schmee

    schmee Poster Extraordinaire

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    But not after warm up? That's a strange one. I wonder if it's the rectifier tube? I know I have a couple amps that hum loudly as warming up but then go quiet. IME a cold solder joint will usually get worse not better with warm up. But I could see what Rob says happening also. Maybe it's just capacitors "filling up"
     
  8. D'tar

    D'tar Tele-Afflicted

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    Well.... Where else would we look;)

    https://robrobinette.com/5F6A_Modifications.htm#Thermal_Image
     
  9. charlie chitlin

    charlie chitlin Doctor of Teleocity Silver Supporter

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    Is this really possible?
    For some reason, I had this idea...but it's not actually based on anything like...actual KNOWLEDGE.
    It's quite a loud crackling right in that 2 seconds when the amp begins to work...not right when I hit the switch.
    It begins, swells in volume as the amp gets up to speed, then goes away and the amp operates normally.
     
  10. schmee

    schmee Poster Extraordinaire

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    I really don't know. I know when you turn some amps off you can hear the caps draining, like a 50cc honda bike a mile away! I dont usually relate crackling to caps though.
    I'm leaning toward a tube or socket. Any crackle if you wiggle a tube?
     
  11. peteb

    peteb Friend of Leo's

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    There is not much in the amp circuit that is going to heat up in that small amount of time.



    What gets hot and why?


    Even before your amp crackles for 2 seconds, the filaments are red hot. Why? It must be like a filament in a light bulb. It must be that the current goes thru something really thin, which magnifies the affect of the current.


    Why does a transformer heat up? Current? Maybe it is not the current but the magnetic flux?



    Why does the cathode resistor heat up? Current working thru a resistance? The power tube has quite a bit of current.



    Why does the tube heat up? It is the plate getting hot. The plate will burn up if there is too much current or too much power. But why? Is it the collisions between the electrons and the plate? Kinetic energy?
















    I have some weird theories that since capacitors hold stuff, they can also hold noise and release it later, but that is really just a thought and nothing more.






    I tried using the thermometer on my DMM. A screw driver measured 62.5 F. I thought, that’s pretty good, the room is 62.5 F. But then I tried to measure hotter and colder and it always measures 62.5 F. I don’t get why.
     
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