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Reunited with my Mesa 400

Discussion in 'Amps and Cabs [BG]' started by BZadlo, Oct 18, 2013.


  1. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    I sold my Mesa 400 about a year ago. I immediately regretted this decision and asked the guy to sell it back to me. Unfortunately, he wasn't interested.
    Got an email from him two weeks ago asking if I'd like to buy it back.
    So...I finally picked it back up tonight. It sounds fantastic! Even better than I remembered.
    Only problem is that this thing (pictured) was rattling around inside. I thought it was a stubby pick at first but it looks to be a cap.
    Does anyone know what it might be for? All of the controls seem to function well. ImageUploadedByTalkBass1382078416.391419.
     
  2. Hi.

    Oddly enough, a quick Google search was quite unfruitful.

    Based on the markings, I'd say it's a varistor though, not a cap.

    Regards
    Sam
     
  3. thekyle55

    thekyle55

    Mar 14, 2012
    That's a MOV, metal-oxide varistor. Most likely it's from the power supply, they're usually used as surge and spike protection.
     
  4. P Town

    P Town

    Dec 7, 2011
    A MOV is typically placed across the AC power line in, after the fuse. You select an appropriate MOV by knowing the operating Voltage, selecting a clamping Voltage, and Joule rating. The higher the Joule rating, the better.
     
  5. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    A power conditioner would already have protectors like MOV's in them, or even an outlet box if you are using one.

    There were two 130 VAC MOV's used on the primary side on the power transformer in these amps. If there is a big spike in the power, these things can blow and would need to be replaced. It is a common part, they even sold them at radio shack.

    It looks like yours was clipped out but it may have always been floating around in the amp from when it was manufactured. Shipping simply dislodged it. If you look inside, see if there are two of these things soldered in near where the power cord connection is.
     
  6. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    Awesome, thanks guys!
    I've had the amp in the shop twice in the past year and was really hoping to not go back again soon (bad tubes twice). I'll take it apart tonight and look for some legs.
    Sounds like this is not a dire repair.
     
  7. FC Bass

    FC Bass Alembic and Mesa/Boogie junkie

    Jun 9, 2006
    Holland
    You might have an empty spot over here:

    [​IMG]

    [​IMG]
     
  8. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    Does that one do the same thing?
     
  9. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Yes, the two green components on the board, marked VR1 and VR2.

    Your amp will work fine without them. They are there to protect the amp in the event of a power spike from noise on your power line or a thunder storm.
     
  10. Yango

    Yango

    Apr 14, 2008
    Earth
    Well, if you happen to get a spike/surge on your next gig your repair will be a whole lot more expensive, that's for sure.

    It's like a seatbelt. You don't need it until you need it—and then it's too late.

    I'd just get it fixed if it were my amp...
     
  11. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    Luckily it doesn't thunderstorm very often here. :)

    Thank you everyone for the help! I was able to sleep peacefully last night.
     
  12. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    I'll check radio shack for the varistor tomorrow.
     
  13. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    Ahhhh, VR2 is missing!
     
  14. Hi.

    Luckily You found it even before you knew it was missing ;).

    Regards
    Sam
     
  15. This thread reminds me that TB is indeed, often greater than FB
     
  16. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    Got a varistor at Radio Shack and replaced it on Saturday. Both of mine were flipped 90 degrees from FC Bass's pics. One of them was siliconed to the side of another component off of the board and the other was broken off. I left the legs long, bent it down and just siliconed it to the chassis.
    Can't say that I notice any tonal difference (guess I'm not supposed to) but the amp works great! SOOOOO glad that I got this thing back! I feel like I can breathe again at rehearsals.
    Thank you everyone for the help!
     
  17. chaosMK

    chaosMK

    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    Great story. I'd love to be reunited with my first Bass 400. It had the stock preamp tubes from the 80's, whatever they were they were awesome. I ended up getting another eventually after trying a few different heads. 400 non-plus is the amp for me.

    Put some JJ KT-88's in it! I am pretty sure they are the best current production power tube for this amp (increased low end depth, silky highs, slight compressed feel). The Tung Sol RI 6550's I am trying now are fine, improvement to power/headroom and all that, but they dont beat the JJs.
     
  18. BZadlo

    BZadlo Supporting Member

    Mar 4, 2008
    Seattle, WA
    I thought I wanted an SVT so I sold the 400 back a year ago. The SVT is too loud for most of the stages that I play. I could never get those power tubes rockin'. So, I moved to a V4-B which I remember being my favorite amp ever. It turns out that I like the 400 more.
    I've got Mesa 6L6's in it now. I love how they knock the power down on the amp. I run it into 2 Ampeg 210 AV's. I have the 400 in a rack bag and I can easily fit my whole setup in my trunk.
    Oh also, I paid $700 for it.
     

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