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Guitar amplifier blew plug sockets

Discussion in 'General Electronics Discussion' started by coffee_king, Apr 24, 2013.

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  1. coffee_king

    coffee_king

    17
    0
    Apr 24, 2013
    Hey all
    I dont really know much about electronics, but dont mind doing a bit of work myself.

    Up until a few days ago my late 1960s guitar amplifier was working OK.
    But the other day when I plugged it in it shorted out the sockets on my upstairs floor.
    It had a 3 amp fuse in the plug.

    I changed it to a 13amp plug and then when I switched it on it went bang at the wall socket and also partially blackened the wall. (Not the best of ideas I guess).

    So any ideas what I should try first to try and work out whats going wrong exactly?

    The main black power lead that plugs into the wall socket does feel quite spongey and I'm wondering if the issue lies with this?

    See attached image.

    Many thanks for your assistance.

    [​IMG]
     
  2. Rleo6965

    Rleo6965

    585
    9
    Jan 22, 2012
    You should not replaced fuse higher than original fuse rating.
     
    Last edited: Apr 24, 2013
  3. coffee_king

    coffee_king

    17
    0
    Apr 24, 2013
    OK, so where do I take it from here then please?
     
  4. dietermoreno

    dietermoreno

    238
    0
    Dec 30, 2012
    Sounds like you have a short and when you replaced the blown fuse with the wrong fuse you blew your wall sockets.

    You never replace a fuse with a fuse that has a higher current rating.

    Use a multi-meter to test the resistances to test for shorts. See my thread titled "Why did my PA fuse blow".
     
    Last edited: Apr 26, 2013
  5. sheldonstv

    sheldonstv

    68
    0
    Jul 17, 2007
    have a look at the mains tx-check the primary for shorts and have a look at the secondary for the same-one fault i had with a unit of this type a while back was a faulty on off switch which failed in a similar way
     
  6. Rleo6965

    Rleo6965

    585
    9
    Jan 22, 2012
    Check the 3 glass fuse if blown. Each fuse have particular circuit load that will cause to blow or open if it had shorted components. If any of this 3 fuse does not blow. Defective component was before this 3 fuse. That is, wire on transformer, transformer, bridge rectifier ( located under the transformer and 2 tall capacitor ). filter capacitors. You can test this components using Ohmmeter.
     
    Last edited: Apr 25, 2013
  7. coffee_king

    coffee_king

    17
    0
    Apr 24, 2013
    Will the capacitors still be holding a charge? If so how can I discharge them?
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    Possibly.

    Measure them.

    If they're not below (say) 20V, discharge them.

    Here is one way to do it.
     
  9. Rleo6965

    Rleo6965

    585
    9
    Jan 22, 2012
    Use the tip of the ac plug of your soldering iron to act bleeder resistor. Touch it the 2 terminal of ac plug to 2 terminal of big capacitors.
     
  10. john monks

    john monks

    693
    2
    Mar 9, 2012
    Your short could be anywhere. If it was me I would plug the amplifier into a variac, turn everything on and turn up the voltage until it started drawing about two amps. Then I would feel for something getting hot. It may be the rectifiers, transformer, or the output transistors. If you don't have a variac you might be able to connect a 100 watt light bulb in series with the line cord.

    The capacitors typically do not have a great deal of voltage in a solid state amplifier so safety may not be an issue with the residual voltage. But if you really want to discharge the capacitors I would place about a 100 ohm resistor in parallel with them. But until you find your short this may be a waste of time.

    This may not be an easy fix. Good luck.
     
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