Help with amp repairs.

Discussion in 'Guitar Gear Talk Forum' started by ultrabot90, Oct 30, 2010.

  1. ultrabot90

    ultrabot90 Like fishes need bicycles

    This MG15 I have (yeah yeah get over the fact that it's crappy and dead sounding and w/e)...the knobs work on some points, not on some others - and it's incredibly fiddly setting them at a position that is working. Sometimes the volume comes but the sound fizzles out in a second after playing and holding something. On some points the sound comes out loud and clear and sustains - yesterday this stopped too, ie the amp was essentially useless without repair.

    Took it to Bhargavas today, they say -
    250 service charges
    Then according to them the knobs need to be replaced, so,
    220 per knob (x4)
    and they say the OD switch needs to be replaced (that isn't working either, but no biggie because I don't use distortion), so,
    190 for one switch
    ...1320 bucks.

    I've held off repair for the moment. Asked the person to whom the amp belongs, suggested we split the cost half, then we decided to take it to where he bought it, OnStage Lajpat Nagar. Figured repair might be cheaper (If you wish to know why I'm trying to repair this amp, it is because I'm ~80% close (financially) to my next amp, which should last me for a while. But that amp could be a little while away.)

    Is the Bhargavas quote a rip off? I need to have an idea for the next trip to the repair shop. Also, anyone know of an amp repair guy around here in Delhi?
     
  2. thehundredthone

    thehundredthone New Member

    Are the pots scratchy on turning? That could be fixed with some contact cleaner. If it's a question of a bad solder joint, that is cheap to fix too. I hardly think the problem's arising from the knobs. Ask them to fix it without changing the 'knobs'.
     
  3. ultrabot90

    ultrabot90 Like fishes need bicycles

    They turn smoothly. Only the sound comes fine at some points, comes and fizzles out without sustaining for long at some, and none at others.

    I'm tempted to pick up a solder, practice-practice-practice using it, and then taking apart the amp - with the owner's permission, of course *bwahahaha* Even if I don't succeed, I'll have a better idea of what the problem might be. I wonder if I might actually be able to make it better by swapping some stuff out?

    Early Google-fu reveals -
    http://webcache.googleusercontent.c...te+amps&cd=4&hl=en&ct=clnk&gl=in&client=opera
    http://www.ozvalveamps.org/repairs/solidstateamprepair.htm
    http://www.ssguitar.com/index.php?PHPSESSID=acad7e3e847ddbc2a50d6bb8a20b3d87&board=15.0
    http://www.ssguitar.com/index.php?topic=439.0

    (I feel this might be going off my track.)
     
  4. flood

    flood New Member

    do you have a working knowledge of electronics and have you worked on circuits before? if you don't, there is a 99% chance that you'll just end up with trash on your hands. like the video game i took apart when i was 5. swapping stuff out at random doesn't work the same way here; this isn't lego. if you fry something else, you'll have additional hassles.

    the quote looks ok, i think. while the parts (pots etc.) aren't necessarily expensive, they're more than likely not available locally. they aren't really charging you for the parts as much as they are for the time spent in changing them. the delhi electronics market (don't even know where it is) is from my knowledge a lot worse stocked than lamington road here or SP road in blore.

    contact spray may or may not work; make sure you use contact spray (e.g. deoxit, kontakt 60) and not a lubricant like WD40. the latter will worsen the situation.

    my assessment - it doesn't sound like the pots are the problem. sounds like a cap somewhere in the circuit has gone leaky or has crapped out, or the power transistors are shot.

    if the store is guaranteeing that they will get it up and running for that money (i harbour doubts, but you never know), i'd suggest you do it. debugging is systematic and arduous, not for the uninitiated and your method WILL not work.
     
  5. ultrabot90

    ultrabot90 Like fishes need bicycles

    One epic DUH. Cmon, what do you take me for? Obviously I'd do a ton of research and then practice around on other (expendable) stuff before taking up the task itself! =|

    But nay, can't give it as much time as I'd like, so no adventures in new learning right now.

    I'll post back on how it goes with OnStage.
     

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