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Potassium Carbonate corrosion on GK 700RB FP jacks??!!

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  • Potassium Carbonate corrosion on GK 700RB FP jacks??!!

    I just opened & removed the GK 700RB's FP PCB from the chassis, as the input jack was broken, and found every FP jack just caked with that blue potassium carbonate corrosion (I think that's what it is) that we're used to seeing on old alkaline batteries that have been left in place too long. I've never seen this on an amplifier though. I hadn't thought to stock vinegar here in the shop, as I read that's one of the solutions to clean that off......I think.

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    I looked at the rear panel speaker jacks, and didn't see that condition on those two jacks. And, I don't see evidence of this corrosion anywhere else on the Front Panel PCB. Before I opened it up, I wasn't sure if I had a replacement jack for that, but know I don't have four of them.

    What would cause this? Anyone else seen this?
    Logic is an organized way of going wrong with confidence

  • #2
    If it's just on the jacks and not elsewhere, I'd suspect someone's poor attempt at cleaning them with something strange. In the old days, radio shack used to sell a "tuner cleaner" that would leave that color residue on parts. Godawful useless stuff.
    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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    • #3
      Weird!

      Unrelated but related: Are you taking photographs with this?

      --
      I build and repair guitar amps
      http://amps.monkeymatic.com

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      • #4
        A P.S to my post #2. If it is just some kind of cleaner/lube residue, you ought to be able to hose them down with a component cleaner, clean them up, and reuse them.
        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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        • #5
          Never seen such corrosion either, agree on user trying some wild concoction on them ... maybe he wanted to resolder them because "he read about it on MEF " and brushed on some great tin soldering flux ... which his Grandpa used successfully to solder tin cans and stuff ...... in the farm in 1939 that is
          50% water, 45% muriatic/chlorhydric acid, as much tin clippings as you can dissolve in the mixture and it stops bubbling.
          Juan Manuel Fahey

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          • #6
            My first tech job was in TV repair back when there were tube TV's and actual knobs for tuning and volume. Tuners would get intermittent contacts. A lot of TV guys would just spray this foamy/gunky tuner cleaner in the holes and call it good. I used to actually take turret tuners completely apart and clean and lube the contacts on every turret (one row of contacts for each channel). They'd often be gunked up with dirt and that same blue/green residue from the last repair guys just spraying more and more of the shit in there. It's a very time consuming task, but done right, they'd be just like new and no more goo to attract dirt. That's what those jack contacts look like to me.
            "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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            • #7
              Probably not the same, but it looks like buildup/oxide ive seen on some vintage tinned wire when ive had to strip it and resolder it.
              If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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              • #8
                Could be. I'd hose them with a contact cleaner. If it runs off, it's residue. If it changes color or stays, it's probably corrosion. Easy enough to find out.
                "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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                • #9
                  Maybe they were stashing blue meth in the Jack's.

                  Snort some and see.

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                  • #10
                    probably not potassium carbonate, which is colorless, it may be copper carbonate
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                    • #11
                      Originally posted by tedmich View Post
                      probably not potassium carbonate, which is colorless, it may be copper carbonate
                      [ATTACH=CONFIG]53078[/ATTACH] which should be soluble in vinegar. Oddly some report Windex (ammonia) works too.
                      I knew I was forgetting something when I left the apt this morning. Vinegar. Well, I'll have to bring some in tomorrow and toss them into the ultrasonic cleaner with some in the vat, if applying some vinegar and/or ammonia. I do have Windex out in my car so I can try that today, at least.

                      I sprayed some of that on, and it seems to have some affect, so I poured enough into the bottom of my ultrasonic cleaner to see what that does. I did order more replacement jacks (both with and without the protruding ground pin from the front surface of the jack body.
                      Logic is an organized way of going wrong with confidence

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                      • #12
                        Originally posted by xtian View Post
                        Weird!

                        Unrelated but related: Are you taking photographs with this?

                        No...........but, by today's standards, just as old. Its' a Sony Mavica FD-73, which stores the jpg files on 3.5" Floppy. Very low resolution. I desperately need a better digital camera.......had one my brother gave me....a small Nikon point-and-shoot, but it's screen was too small, was using the video output jack to feed a larger monitor, then I no longer got video and it's dead, with no way to tear into it to repair that. So, I've been using this horrible camera and doing what I can with it for the time being. Sorry..........
                        Logic is an organized way of going wrong with confidence

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                        • #13
                          Corroded jacks after 1/2 hr in ultrasonic cleaner using vinegar

                          Originally posted by nevetslab View Post
                          I knew I was forgetting something when I left the apt this morning. Vinegar. Well, I'll have to bring some in tomorrow and toss them into the ultrasonic cleaner with some in the vat, if applying some vinegar and/or ammonia. I do have Windex out in my car so I can try that today, at least.

                          I sprayed some of that on, and it seems to have some affect, so I poured enough into the bottom of my ultrasonic cleaner to see what that does. I did order more replacement jacks (both with and without the protruding ground pin from the front surface of the jack body.
                          This morning, having brought in both a small bottle of vinegar and ammonia, I poured in enough vinegar into my small ultrasonic cleaner vat and put the corroded jacks in, along with inserting the plug portion of some Switchcraft 280 phone plugs to open up the contacts during the cleaning operation.

                          It changed the color of the corrosion, but didn't make them usable. The inside contact surface where they engage the phone plug also looks terrible. And, the vinegar attacked the tin plating of the frames of the Switchcraft plugs (as well as on the jacks), which were shiny when I began, now dull and murky looking. So, I won't try that again! The corrosion was well caked on, and they're gonners......into the trash, as I was planning on before I began. The replacement jacks came in yesterday, so this was just an exercise in desperation that didn't pan out.

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                          Logic is an organized way of going wrong with confidence

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                          • #14
                            Sorry for that.

                            Vinegar is diluted acetic acid and tends to attack most (plated) metals especially if the plating is no longer perfect. The plating of the contacts should be nickel. And the blueish stuff will be a nickel or copper salt (probably a chloride caused by outgassing of PVC plastics).

                            I would have tried:

                            - warm water, as salts often dissolve in water - maybe with a little ammonia or liquid soap in the ultrasonic bath.
                            - Deoxit and a toothbrush, because this is what it is meant for - loosening corrosion products like salts and oxides

                            Not sure if this would have cured the problem, but both methods won't make things worse. And I have been using the combination of both methods (warm water followed by Deoxit treatment after drying) successfully on contacts corroded by leaking batteries. Just don't expect a shiny like new surface after the treatment of strongly corroded contacts.
                            Last edited by Helmholtz; 03-26-2019, 06:11 PM.
                            - Own Opinions Only -

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