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Faulty amp

Posted by Tommy on January 22, 2011 at 10:12am in Building Secrets, Tips, Advice, Discussion

I bought a cheep amp from a pawn shop. Whenever i turn the knobs the speaker cuts out...

 

I have to tweek the volume all the time to keep it going. Could this be a loose solder joint somewhere, earthing problem or is the amp simply dieing ? ?

I had plans to re house the amp into another box, now i think the amp is bust so not sure weather to use it or not. 

 

HELP !

 

The amp model is a Westwood GA-15

westwood amp.jpg

westwood inside.jpg

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Replies

  • Tommy January 27, 2011 at 10:24am

    Thanx for all your advise guys. I have the day off tomorrow so im going to have a crack at fixing the amp.

     

  • MichaelS Country Boy Guitars January 25, 2011 at 5:58pm
    Petey you should change your name to Petey Fluxfinger, just a thought. : )

    petey twofinger said:

    look at the solder for the pot (volume control) it may have a tiny crack in it . just heat all three up and re-set em to be sure . if it crackles when you spin it , the pot is shot . you can clean em , sometimes . replacing it is the way to go . look at the back , is the value written on it ?

     

    if not you can ohm it out by turning it all the way down and seeing the resistance with an ohm meter . get a replacement of the nearest value , and style . they have different shafts / sizes so .

     

    i wouldn't worry about heat . pots can usually take quite a bit ! and unless a chip is right near it . . . the only equipment you would need to remove a pot is a soldeing iron , sure you could use a de-solder bulb , or de-soldering braid but if someone had a gun to your head , you could prolly remove the pot with a bic .  pots are like 3 to 5 bucks so . 3 solder joints . its prolly like a 100 k , could be a 50 or a 500 though . personally i try and collect pots from scrap electronics . finding the ones that are threaded is a challange these days . i hate to buy em though !

     

    and yes , i use plumbers flux on everyfuckingthing .

  • petey twofinger January 25, 2011 at 3:46pm

    look at the solder for the pot (volume control) it may have a tiny crack in it . just heat all three up and re-set em to be sure . if it crackles when you spin it , the pot is shot . you can clean em , sometimes . replacing it is the way to go . look at the back , is the value written on it ?

     

    if not you can ohm it out by turning it all the way down and seeing the resistance with an ohm meter . get a replacement of the nearest value , and style . they have different shafts / sizes so .

     

    i wouldn't worry about heat . pots can usually take quite a bit ! and unless a chip is right near it . . . the only equipment you would need to remove a pot is a soldeing iron , sure you could use a de-solder bulb , or de-soldering braid but if someone had a gun to your head , you could prolly remove the pot with a bic .  pots are like 3 to 5 bucks so . 3 solder joints . its prolly like a 100 k , could be a 50 or a 500 though . personally i try and collect pots from scrap electronics . finding the ones that are threaded is a challange these days . i hate to buy em though !

     

    and yes , i use plumbers flux on everyfuckingthing .

  • Vagabanjo January 24, 2011 at 5:39pm
    I agree, my first fix would be wrongly or rightly, to sprat the switch with WD40, then look at the solder, and like Mark says, if you are uncomfortable resoldering or replacing there must be someone local who can do the job, maybe ask at your local music shop. I have a similar problem with a small Marshall I have, but as I don't use it much I just can't get round to trying to sort it. (a quick bang gets it back on track though!
  • Mark Bliss January 22, 2011 at 11:52am

    I agree that the most likely problem is with the potentiometers, they frequently act up in that manner, especially if they have been exposed to the elements..... Humidity etc.

    Cleaning may help, but it may only be a partial improvement proving the theory. Replacement isnt that hard if you have the equipment to desolder without excessive heat. If you arent comfortable with that, perhaps you can find someone who does that sort of thing.

  • Dan Sleep January 22, 2011 at 10:56am

     It could be a loose solder joint. You could test that by wiggling the wires around. It could also be dirt or corrosion inside the volume control. If this is one of those amps where the volume control is attached to the circuit board, then you would have to do some heavy duty soldering to replace it, but it could be done.

     

    You could also get some contact cleaner and see if you can spray some inside the volume pot.

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