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Bass Amplifier troubleshooting

Discussion in 'Troubleshooting and Repair' started by RubiconJoe, Jul 3, 2015.

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  1. RubiconJoe

    RubiconJoe

    22
    1
    Oct 7, 2014
    Sorry for the delay again. Well I have kind of good news regarding this repair. I ordered two new 3300uF filter caps and tossed them in this morning. Now the constant buzzing is not there anymore and I do get amplified sound from the speaker. I re-assembled everything and tried it out again and noticed that the sound is very distorted. I took the amp apart again, (not-powered and unplugged of course) and whenever touching the chassis or any wiring or poking components, I am getting some popping from the speaker. What would this indicate? I noticed this when first troubleshooting and mentioned in my first post. But now it happens when anything is touched. Maybe still a faulty ground or bad op-amp or something?

    What do ya think? Thank you again for all the support so far!

    Joe
     
  2. RubiconJoe

    RubiconJoe

    22
    1
    Oct 7, 2014
    Actually just found that wiggling the input jack can get the problem to go away. Tried re-soldering it and a few of the ground connections on the pots. Still no luck. Any suggestions on finding a bad ground connection?
     
    Last edited: Aug 15, 2015
  3. Martaine2005

    Martaine2005

    3,554
    966
    May 12, 2015
    Sounds good so far. Touching and popping is you grounding it like when you touch the jacks.
    Looks like it was the caps and the input jack all along.
    Well done for sticking with it.

    Martin
     
  4. RubiconJoe

    RubiconJoe

    22
    1
    Oct 7, 2014
    I am still having a slight issue with the amp. I changed out the input jack and still sometimes get a distorted sound out of the speaker sometimes. I can wiggle the jack to a point where it stops and will be fine unless touched again. The circuit board is up on stand-offs and I don't believe anything is shorting to the chassis. I poked around the board while strumming to try and find the culprit but cannot seem to narrow down where exactly the issue is. I inspected all solder joints again, but could not find any that look faulty. I do not what else to do other than to re-solder every connection of this board?

    Like i said before, the speaker makes popping sound while the amplifier is off if it gets moved around or poking around the circuit board, or even touching the outside of the chassis. I can see this happening while the amp is on, but it is not powered on!
     
  5. Martaine2005

    Martaine2005

    3,554
    966
    May 12, 2015
    Hi Joe, sorry, I thought you sorted it!! I misread the post.
    Well, I don't really know what to suggest. When off, does it 'pop' when YOU touch it or poke it with a non-conducting stick?
    If it's when you touch, it sounds more like static. But when it's OFF I don't understand either.
    I don't think this would have anything to do with it but are the bleed resistors for the main caps ok?
    Are you sure there is no break in the power cord ground to the wall plug?

    Have you tried a different guitar input lead?
    Are you sure it's not the guitar?
    Sorry, I am out of ideas now. Hopefully someone else will chip in.

    Martin
     
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