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Cleaning Old Soda Off Of A Circuit Board?

Discussion in 'Electronic Basics' started by phaeton, Mar 16, 2007.

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  1. phaeton

    phaeton Guest

    Hey y'all. Been awhile since I've been here. I've missed the joint.

    I might be picking up an old SS Fender bass amp from a guy at work for
    dirt cheap. Like buy him a case of beer and it's mine, cheap.

    Anyways, I don't know the details, but at some point in its
    illustrious history, it was laying on its back, and a Wild Cherry
    Pepsi got dumped onto it. Supposedly the speaker is fine, but the
    soda seeped into the front panel of the amp, into all the pots and the
    eq sliders, and most likely down onto the circuit board.

    The good news is, it still works, it just sounds like shit. They say
    it's kinda distorted, makes noises, and the volume fluctuates
    constantly while you're playing. It can go from normal, to whisper,
    to OMFGTHEWALLSARECRACKINGLOUD (in true Fender style) on whatever whim
    it wants. Sounds like dirty/gummy pots to me. I fixed this on my old
    Peavey Pacer many years ago with a $10 can of Contact Cleaner/
    Lubricant from Radio Shack. (No soda in that case, just age and
    dirt).

    The other good news is that shortly after this happened, the guy and
    his brother took it all apart and tried cleaning it up with Isoprophyl
    Rubbing Alcohol. Hopefully this means that it hasn't had a lot of
    soda on the circuit board for the last few years. However, something
    tells me that the water content and lack of lubricant could seize the
    pots.

    I still have most of a can of that Contact Lubricant, and I'll happily
    buy more if necessary. It'll probably work on the pots and sliders if
    I treat them several times. If not, I could always replace them all.
    Do you think it will also do any good (or harm) on the rest of the
    circuit board? At this point, I almost wonder if gently agitating the
    board in warm distilled water for awhile would do any harm, and/or
    maybe some good.


    I don't have it here yet, so I haven't taken it out to look at it.
    It's very possible that the whole thing is a wreck, and if that's the
    case I at least have a cabinet and (hopefully) a good speaker. I
    might pick it up this weekend so I'll take a look then.

    Thoughts?
     
  2. Guest

    With dirty equipment I've found over the years that fancy alchohols
    and degreasers are a waste of time and money. The most effective
    cleaning method is to be brutal and use a mix of really, really hot
    water and washing up liquid dispensed by a pressure sprayer (one of
    those pump up things). Particularly bad patches attended to by use of
    a paintbrush.
    It's essential that a thorough rinse in clean hot water is given
    afterwards (pressure sprayer again), followed by drying at a high
    temperature (say 40degC) for as long a time as possible.
    Dishwashers can be even easier if the parts will fit in.
     
  3. Lionel

    Lionel Guest

    That's a big plus. I've fixed lots of equipment that's suffered drink
    spills (coffee, coke, wine, beer, etc), & the single biggest factor
    that determines whether it survives is how fast the power is removed &
    the gunk washed out.
    Yes, absolutely.
    If you're careful, it's a good idea. After you wash the board, you
    also need to wash in alcohol. The important thing is make sure that
    it's 100% dried out (gently!) before you next apply power. I put
    boards on a folded towel & sit them in a dry, warm (30-40c or so)
    place for at least 3 days to make sure that all the crevices (like
    under chips) are totally free of moisture. The alcohol helps a lot
    with this.
    Go ahead. But you may need to replace the pots anyway.
     
  4. Use clean water with baking soda dissolved in it. Rinse off and let dry for
    a week.
     
  5. Phil Allison

    Phil Allison Guest



    ** That is the EXACT method I have been using with 100% success for many
    years to clean PCBs and heatsink modules contaminated by drink spills or
    just accumulated grime blown in by a fan.


    ** Ain't got one of them.

    Be neat to dump a whole power amp in one ....



    ........ Phil
     
  6. MassiveProng

    MassiveProng Guest

    Microwave some 99% IPA up and give it a good hot alcohol bath.

    Not assembled. Break it down into subassemblies, like the panel,
    etc.

    Being hot, the IPS should dislodge the soda remnants and surupy
    slurry.

    Then a good bake out in a 60C oven (140F). THEN, add the contact
    spray, which might have some dry lube in it for the pot shafts.

    Otherwise, replacing the pots that are sluggish to turn would be a
    good step.

    If you hot dip the PCB assy., keep from dipping any transformers or
    inductors as the tapes used will have their adhesive backings
    released, and the bake step above needs to be about a half hour, for a
    PCB where you did get a transformer "wet", it would need an hour bake.
     
  7. MassiveProng

    MassiveProng Guest

    Bake for an hour at 60C.
     
  8. JeffM

    JeffM Guest

    That's going to make it fun.
    Phil Allison wrote:
    #Be neat to dump a whole power amp in [a dishwasher]
    #
    Seems like that's what it might take
    --if cleaning would work on all the bits.
    I'd brace myself for the probability
    that the panel-mounted parts will have to be replaced.
    I agree with everything you have said
    ....except one detail:
    A paintbrush has soft bristles. An *acid* brush
    http://www.solobrushes.com/pictures/pseries_lg.jpg
    with the business end trimmed short for even more stiffness
    is the tool.
    Any place that sells industrial supplies (pastes) has them.
     
  9. Rich Grise

    Rich Grise Guest

    Wash it with carbonated water (club soda). That will get the water-
    soluble sugars off of it, which is what gums things up. The contact
    cleaner things are usually non-polar solvents, and sugar will just
    shrug that off. And blow it dry, don't bake it dry - baking leaves
    crud behind. With dry clean compressed air, the liquid water gets
    blown away and takes the crud with it.

    I used to fix video games and pinballs that were located in bars -
    it's amazing what kinds of crud can get on boards in that kind of
    venue.

    Of course, it's nothing like cleaning medical devices that have been
    dropped in a bedpan. =:-O

    Good luck!
    Rich
     
  10. MassiveProng

    MassiveProng Guest


    Blowing on it does remove any (most) solids as the water/solvent gets
    pushed off, but baking is STILL required. Especially for a water
    /"club soda" wash, as PCBs are hygroscopic.

    Get a clue, grisetard.
     
  11. MassiveProng

    MassiveProng Guest

    Funny, since the "boards" on a pinball are in the cabinet behind the
    backglass.
    Funny, since practically all "medical devices" are immersible.
     
  12. Lionel

    Lionel Guest

    Lots of pinball machines have huge PCBs (& usually the PSU as well)
    directly under the playing field.
    Lots of them are, but not "practically all".
     
  13. Rich Grise

    Rich Grise Guest

    Well, actually, I've seen EM (electromechanical) pins that have
    point-to-point circuitry right on the bottom of the case, under
    the playfield, but the PCB ones usually put the PCB behind the
    backglass.

    The problem is a lot more prevalent with stand-up and cocktail
    videos - but in either case, you'd be surprised where people can
    spill their drinks!
    Big Dork simply has no clue - he's best left ignored.

    Cheers!
    Rich
     
  14. MassiveProng

    MassiveProng Guest


    So are you, asswipe. Upright video games and cocktail versions of
    upright video games are NOT pinballs, you retarded ****.
     
  15. Lionel

    Lionel Guest

    Yes, I've seen those too, although it's been quite a few years.
    Nearly all the ones I've seen have PCBs behnd the backglass, & under
    the playing field.
    I worked at an arcade for a while as a teenager, & nothing like that
    would surprise me. ;^)
     
  16. phaeton

    phaeton Guest

    Well, I got it home. The preamp and power amp are two different
    boards connected by ribbon cable. Strangely, all the soda is on the
    power amp board in the back. Further investigation reveals that the
    amp was not 'on' at the time of the spill. It has been turned on
    since the initial cleaning, and that's how they know it sounds like
    crap. I haven't turned it on to try it out.

    Lots of gunk everywhere, bridging traces and leads, but nothing looks
    burnt and black or anything.

    In lieu of a pump-up pressure sprayer, would a DIY car wash gun work?
    Most of them have a 'low pressure jet' that's on by default, until you
    squeeze the trigger (for high pressure). How about if I saran wrap up
    the transformer and pots and hit it with the low pressure only, then
    rinse well, and let it sit up in a sunny place for a couple of weeks
    to dry out?

    The sliders and knobs were really sticky and stiff, and I went ahead
    and blasted them with the Contact Cleaner. All but one slider
    improved in 'feel'. I'm going to let them sit a day or so, blast
    again, and then track them with an ohmmeter to see if they follow the
    curve like they should. If they don't, I won't be heartbroken.

    Thanks for the help and suggestions thusfar.

    -phaeton
     
  17. It is not at all important that you blast the water in with
    any force. All you need is its ability to dissolve the
    sugars and slats left behind, and a simple stream will do
    that. So you should be able to use a low pressure stream
    and avoid dumping it through the transformer (unless it has
    soda run through it). The contact cleaner you have used
    will make it harder for the water to wet the surfaces
    originally contaminated, so you may have to start with a
    flow of water mixed with dish washing detergent to get under
    the oils in the contact cleaner.

    When everything looks clean and just wet, a thorough drying
    is all that you should need to test the unit. Then, if the
    pots are noisy, a little contact cleaner might help
    lubricate them.
     
  18. Lord Garth

    Lord Garth Guest

    Don't use tap water or mineral laden drinking water. Use
    distilled water. If there is no plastic in the way, I chase the
    water with methyl alcohol then blow it dry.
     
  19. Guest

    The great bulk of the wash can be done with warm tap water, even hard
    water. Just the final rinse is best done with distilled water.
    Before that, the contamination being washed off is dirtiuer than the
    tap water. No sense rinsing gallons of distilled water down the
    drain, brown with Coka Cola.
     
  20. Lord Garth

    Lord Garth Guest

    Okay, that makes good sense. I had DI water available from a tap
    so it was never an issue. I also used nitrogen to dry the parts, also
    from a wall tap.
     
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