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Mesa Mpulse 600 input problems.. help??

Discussion in 'Amps and Cabs [BG]' started by Jsuwinski777, Nov 20, 2018.


  1. Jsuwinski777

    Jsuwinski777

    Mar 1, 2017
    I purchased a used Mpulse 600 on Reverb. When I opened it out of the box and hooked it up to my Fender 610 pro Cab I was blown away by it. It is a tone beast and I can see why it is highly regarded on here. I noticed two of the EQ knobs were scratchy , but I fixed that right away with some electrical contact cleaner. The main issue with my amp is that when plugged into the active input ( with my Peavey cirrus and Ibanez prestige active basses) it works for about 10-20 seconds and then it gets a loud popping, scratchy, ugly sound.. on the active input it is unplayable. The passive input seems to work fine. This is the 1st gen model with the two separate inputs ( no switch). Can anyone guide me in the right direction as to what to do to fix this issue?
     
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    By any chance did the "contact cleaner" get onto the preamp circuit board? What kind of contact cleaner? There is high voltage and sensitive nodes that can be affected by leakage currents.

    It's very unusual for noise to be generated by the peq pots, it's possible that spraying into them might have masked the real cause of the noise.

    It's also possible that there is a problem with the input switching, but this is not the typical symptoms.
     
  3. Jsuwinski777

    Jsuwinski777

    Mar 1, 2017
    No, I sprayed the contact cleaner on the knobs after I noticed the problem with the active input
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    What did you use?
     
  5. Jsuwinski777

    Jsuwinski777

    Mar 1, 2017
    Cdc electrical contact cleaner from AutoZone. I have used this for a whe now and it always does the job
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Well, hopefully you haven't ruined anything yet. Very much the wrong product for the job.

    I'm going to suggest that you contact an authorized service center before causing any additional damage.
     
  7. BogeyBass

    BogeyBass

    Sep 14, 2010
    Omg here we go lol
     
    aproud1 likes this.
  8. aproud1

    aproud1 Don't surround yourself with yourself. Supporting Member

    Aug 13, 2007
    Cincy, OH
    A story heard before?
     
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The type of lubricant and the type of solvent also play a big factor in the safety to the substrate and the stability of the lubricants used in a potentiometer.

    There is also the issue of resuidal substance on the PCB which can destroy the breakdown voltage between traces.
     
  10. BogeyBass

    BogeyBass

    Sep 14, 2010
    Yeah I think there was a 2 or 3 page argument on contact cleaners.

    What to use, what not to use.
    One guy says lubed ( green can
    Other guy says dry. ( Red can

    One guy used lube and supposedly ruined his amp forever. But not really...then possibly really. Experts say this one. People that make the stuff say different.
     
  11. BogeyBass

    BogeyBass

    Sep 14, 2010
    Anyhoo you probably got wonky jack.

    Might be corrosion or the jack switch a Doo.

    Yell at it and unplug it and re plug it in 20 times lol. Too clean it. But their Probably internal switches that need a squirt

    I won't say bad solder connections though. Cause that doesn't ever happen lol.... atleast with " quality products"
     
  12. BadExample

    BadExample

    Jan 21, 2016
    Injiana
    Take yer meds BB.
     
    agedhorse likes this.
  13. Jsuwinski777

    Jsuwinski777

    Mar 1, 2017
    Well guys I sprayed the active input jack and boom! Works great with no issues now
     
    agedhorse and Red Planet like this.

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