Is this “Melted” White Substance in Markbass Head Normal?

Discussion in 'Amps and Cabs [BG]' started by OldFenderPlayer, Sep 26, 2021.


  1. 2A13BBF1-9794-4566-94D6-B31FB0F48A64.jpeg I took the top off my 2016 or 2017 Markbass Tube 800 bass head to spray contact cleaner on the pots to eliminate noise from the Master Volume control and noticed multiple instances of a hard, white substance that appears to have melted in over 30 different locations around the circuit board. The contact cleaner solved the noise problem and the head appears to be working as it should. Does anyone have any idea what this substance might be? Is it cause for concern? I looked at interior photos of other Markbass heads and didn’t see this curiosity.
     
    Peter Torning likes this.
  2. tenor.gif

    It looks intentionally, but sloppily, applied
     
  3. Wood and Wire

    Wood and Wire

    Jul 15, 2017
    gruesome-banner-thestuff.jpg

    A1mQjPSDY7L._AC_SY741_.jpg
     
  4. JTE

    JTE Supporting Member

    Mar 12, 2008
    Central Illinois, USA
    It looks like a substance applied to prevent components from moving, an epoxy perhaps.
     
  5. two fingers

    two fingers Opinionated blowhard. But not mad about it. Gold Supporting Member

    Feb 7, 2005
    Eastern NC USA
    This. @agedhorse will know what it's called. I forget.
     
  6. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    Yes, it’s generally called goop in the industry. As mentioned, it stabilizes components and makes the amp more road worthy.
     
  7. I am worried about that pot you sprayed with contact cleaner.

    What did you use?

    Contact cleaners are too harsh and dissolve the grease eventually killing the pot. They are great for two metal pieces that will mate together (contact), not for moving parts (pots).
     
  8. D8D04D8C-1674-4B68-B3FA-ED82AF6408F6.jpeg
    I used CRC QD Contact Cleaner and it did the job. CRC’s website lists it as an electronic cleaner for sensitive parts. I needed to do something because the grinding noise when I’d adjust the Master Volume was unbearable, and would go from barely audible at 9 o’clock to way too loud at 10 o’clock.
     
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    The white stuff is an adhesive to stabilize components, it's not uncommon.

    The CRC QD cleaner is the wrong stuff to use. It's NOT recommended for carbon or conductive plastic pot elements, only for metal on metal contacts. It does not contain the proper lubricants for the elements and the solvents will wash (different types of) lubricants away from where they are needed. IF you were able to get it into the pot, the problems you will have will show up later and the only choice will be to replace the part.

    upload_2021-9-26_19-11-38.png

    Out of curiosity, how did you get the "magic cure-all spray" into the pot? It's a sealed part.
     
  10. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    CRC QD CC is a non-lubricating solvent based cleaner, it will leave the pot rotation feeling rough and shorten the life of the pot due to abrasion. A lubricating cleaner such as Deoxit D5 would have been a better choice. It can be sparingly applied now, after the CRC cleaner to lubricate the surfaces.
     
  11. I watched a few videos on cleaning dirty pots and noted the products they used. The Master Volume knob is recessed, so I removed the top and there is a small square opening in the upper corner of each pot. I sprayed the pot three times, turned the knob several times after each. After 30 minutes of drying, I reassembled and it worked like new. I played my upright bass through a Fishman Platinum Pro into the amp and was able to turn the amps Master Volume to 3 o’clock with not a hint of static. I can see where where what I used may have been the wrong product, but I’ll find something that will re-lubricate the pot. But for now I can use the amp, which wasn’t the situation this morning.
     
    SC Bassboy likes this.
  12. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    I'm looking at one of those pots and don't see any openings. Here is a picture of the pot, that indentation on the right is a solid rivet:
    upload_2021-9-26_19-30-51.png

    The videos on cleaning pots are just about as good as the videos on "DIY brain surgery", what they don't mention is how important the details are... the proper substance (of everything I have tested over the last 40 years, the DeOxit D5 is the best and the safest by far) and the tiniest amount possible prevents lubricants being washed from where they belong to where they do not belong.

    Since the pot is sealed, it's possible that simply rotating the pot even 10 times may clear up the problem without any magic cure-all spray. This may be the best possible result for you.
     
  13. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    Good rule to follow, never apply a circuit cleaner down the shaft of a pot. Stew-mac sells a tool for doing this, they have no concept of the engineering. The shaft libricant should not get onto the wiper or resistive surface. Applying a solvent along the shaft dissolves the shaft lube and can drive it inside the pot. This can destroy the resistive surface with time.

    Sometimes a crackel is not the pot but broken solder joints or a bad capacitor in the circuit. Since the CRC appeared to fix it, the pot was probably the issue. The fix that you applied could lead to problems with time though.
     
    Last edited: Sep 27, 2021
  14. john m

    john m Supporting Member

    Jan 15, 2006
    Watching a few videos can be helpful but can also lead you down the wrong path.
    I’m glad you didn’t say “I did some research……..”
     
    JacklegBass likes this.
  15. deff

    deff Supporting Member

    Oct 15, 2018
    Gloucester, MA
    Hmmmm. Weird, I've never hear it called that. I gotta look out for that one. The most typical nomenclature I have heard for ruggedizing components and stabilizing them, is glob top, (internal component material), Potting, yes just like on pickups. and then there is conformal coating. Most manufacturers I have run into would call that potting material, even if it isn't wholly accurate.
     
    beans-on-toast likes this.
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Glob top is a very specific material or process used with COB construction.

    Goop, is a non-acetic acid based curable silicone material used to secure larger electronic components against movement and vibration.
     
    SgtHulka, One Way, Bassiclees and 3 others like this.
  17. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    I guess it depends on where you work. Manufacturers have what they call a goop sheet which shows where to apply the material. It’s automated on some lines, otherwise done manually. You really want it placed properly.

    Some transformers are still potted, I see it more so with toroids. Potting with epoxy or wax is still common with radio frequency coils. Conformal coatings for harsh environments, I hate that stuff.
     
    deff likes this.
  18. Fitz

    Fitz

    Oct 20, 2009
    Big fan of CRC. I like to flush really cruddy pots on vintage equipment with CRC, like completely flush clean. Then I follow with either DeOxit D5 and/or FaderLube in a relatively light application.

    I find if I just go straight in with DeOxit, it can sometimes keep dirt and stuff inside, almost like it kinda sticks/slides around on the lubricated surface. I like applying DeOxit or FaderLube to a completely clean pot.
     
    shnapper likes this.
  19. deff

    deff Supporting Member

    Oct 15, 2018
    Gloucester, MA
    Yup, just never heard the word goop used before.
     
    agedhorse likes this.
  20. shnapper

    shnapper

    May 1, 2005
    To the OP…

    I’m sure your pot will be ok, it’s not gonna blow up… CRC would be out of business if catastrophic things were to happen. :thumbsup:

    I have a can of the exact stuff you have pictured, in fact I’ve had the can for nearly a decade. I bought it to spray the contour and master volume pots on my 700RBii nearly(you got it)a decade ago. My amp is fine the pots are fine.. That’s my story and I’m sticking to it. :D
     
    Last edited: Sep 27, 2021
    BrentSimons likes this.
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    Oct 25, 2021

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