HELP! Headphone output sounds clean, speaker sounds distorted

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Firehouse, Mar 9, 2015.

  1. Firehouse

    Firehouse Member

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    LEAD IN
    Hello. I picked up a Fender Sidekick Reverb 25 a while back for a very nice price, and it needed a little fix (I think the reverb wasn't working, other than that it was fine). I got it working and replaced a few pots that were falling apart, two of which were the wrong type, since that's all I had at the time (linear instead of log, wrong but close resistance).

    At this point the amp worked fine, save a volume knob not doing much at all (it has a master, and it got louder than I needed in my bedroom, so that wasn't an issue). The other day I received some pots in the mail, so I switched them into the amp so the specs would be right, which fixed the volume knob problem.

    THE PROBLEM
    I'm not sure what happened, but now the amp is distorted using the speaker wire outputs. I've tried the speaker with another amp, and this amp with other speakers, so I know it's the amp, not the speaker. The headphone output sounds fine, Fender clean and all.

    WHAT I'VE DONE
    The only pots I replaced were the reverb, presence, and volume controls. I also jumpered a resistor next to the reverb pot so I could get more of a Ventures type wetness when turned all the way up, but switched back to a resistor to try to kick the radio that was coming in (which I'll switch out again, since I used a random resistor, and it didn't really get rid of the radio like I was hoping. Reverb sounds nice though). But I did this the first time around, before things started going wrong. Through all this there has been a little PCB damage from soldering, but only around the pot replacements. A couple wires came loose through flipping the circuit board over so many times, but I've soldered them all back into place as far as I can tell.

    I'm obviously not an amp tech, but I'd like to get to the point where I can diagnose and fix the problems I run into, and maybe more if things go that way.

    My soldering on the pots is darn near atrocious, especially since the PCB was breaking down as I was soldering, but since they're all working fine through the headphones, I don't think that's the problem.

    I haven't been able to find anything mentioning this problem. Does anybody have a clue what's up? I'm eager to learn, but sometimes I just hit a roadblock like this one and need some help. Any replies are greatly appreciated.
     
  2. Firehouse

    Firehouse Member

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  3. dtube

    dtube Member

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    Way North of Pittsburgh...no, I don't own a banjo.
    The headphone jack is a switching-type unit that passes signal to the speaker if nothing is plugged-in. Try cleaning that jack first. If that doesn't fix it, get a replacement.
    -D
     
  4. Firehouse

    Firehouse Member

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    Thanks for the reply dtube.

    Okay. Does the jack change the overall signal... uh...(I'm sure there's a word for what I'm trying to say, I just don't know what it is). Since I bought it cheap and am still pretty new at this, I did some poking/alli clipping around, and connected the signal output before it went to the headphone jack straight to the speakers, and it still sounded distorted. I guess that should be normal (right?), since that's the only thing feeding the headphone jack, which sounded fine.

    I desoldered the headphone jack to see what I could see, and then did a little prying to see how it worked, and eventually opened it up, so I think I'll get a replacement to be on the safe/sure side. I really like this amp for a nice SS practice amp, so I'll be excited to see if this fixes it. I'll let you know either way.

    Thanks again. You may have just saved a defenseless little amp from the hands of an uneducated tinkerer.
     
  5. Firehouse

    Firehouse Member

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    As a side note, would it be possible to bypass the headphone jack altogether, and just hardware past it? If I have to get a new headphone jack I will, but I have other amps/ways of putting my guitar into headphones, so it's not a huge concern of mine.
     
  6. pdf64

    pdf64 Member

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    Yes, hardwiring across the switching jack would solve it, if that is the issue.
    Ensure that you don't hardwire the signal to ground, as that may damage the amp badly.
     
  7. Firehouse

    Firehouse Member

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    I hardwired the headphone jack, but the real problem might have been with the ground. The big metal part that connects to the chassis had some poor connections that probably came loose at some point, so I rewired them all and it's back in working order. Even if it wasn't the headphone jack in the end (I don't even know at this point...) I really do appreciate the help. This little baby's back in action! Thanks you guys!
     

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