So I opened her up...(Mesa .50 Cal + problem)(pictures included)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Trego, May 26, 2008.

  1. Trego

    Trego Member

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    I figured I would open up my Mesa Boogie .50 Caliber + combo before I sent it off to a tech to tell me something that I might have been able to figure out myself.

    It looks like there are two problems, both of which I was hoping you guys could help me figure out how to address. The both of which have to do with the spring reverb. There are three springs on the reverb unit and one of them has been disconnected. Does anyone know how to reattach it? Also, there is a very thin wire going from the reverb unit to the board that has broken. Can I solder the wire back together, or should I get a totally new one? Could I just use some electrical tape?

    I don't know much, but I have plenty of time to learn (looking for a job after just graduating from school.)

    Here's the pictures:

    [​IMG]

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    and here's a video talking about the issues I see:
    http://www.youtube.com/watch?v=7H2vTqFam9o

    and here is an older video showing the issue that this damage created:
    http://www.youtube.com/watch?v=O18__YG5qTw

    Blessings, Matt
     
  2. tim boehlert

    tim boehlert Member

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    Matt:

    You can probably re-attach the spring, using some fine needle-nose pliers BUT the broken wire is the real problem - difficult at best to repair that without special skills/tools I think.

    Try to find a replacement on-line (probably less than $20-$30 at most). The wires are the electrical connection between one end of the tank and the other, and are so fine as to be extremely unlikely to re-solder.

    If the .50 cal has an EFX loop, you could always just discard the tank and go with a BOSS RV pedal or similar as well. It won't break again, and you can dial in exactly what you want with more precision.

    Okay: So I went back and watched the videos - you can probably solder THAT wire with the proper soldering iron (NOT a soldering gun type). It's hard to see the spring end, but they usually just attach to the casing via a small tab for mechanical stability. I've never seen a tank hard wired into an amp like this, so the only thing you could to really eliminate it as THE cause of your problem would be to unsolder the OTHER end BEFORE you attempt a fix. That should eliminate it from the circuit. Most tanks are hardwired to the circuit via RCA jacks. Now based on those ideas, it really sounds like the amp was dropped or mishandled in some way to cause both of those disconnections. If that is/was the case, you'd want to look for broken connections elsewhere in the chassis. If the amp only makes that noise when you tap on the housing near the ON?OFF switch, start there. Use a wooden chop-stick while the unit is running to do the same tapping test. Try each of the components, prod them, tap them. You MAY be able to isolate the problem with this simple test. Look for any arcing components or evidence of arcing - burnt or discolored components - it could be a resistor (that's what it sounds like) so start with those first. Check all of the hardwired connections, even pushing downward on the circuit board.

    If you can isolate it to a part, you MAY be able to replace it yourself, but only if you know what you're doing AND have the proper replacement(s). Otherwise, spend the cash and have it done by a qualified tech, either at Boogie OR one of their qualified network techs. The amps are built like tanks generally, and so should also last you a lifetime. I've owned Boogies since 1979, and have NEVER had a complete failure, even AFTER dropping them!


    Good luck!
     
  3. Dave C

    Dave C Gold Supporting Member

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    Reattaching that spring is a tougher job than it would appear having done a few of these and probably not worth the effort it would require on what looks to me like the guts of a type 8 Accutronics short tank ($23 at AES). The wire should be an easy solder fix. It would require you to remove the reverb assembly to reattach the spring anyway ...so I would suggest ordering a replacement and doing the job once. Until the replacement arrives I would reattach the wire and either snip out that loose spring or secure it to something because you do NOT want it flopping around in your amp where it could contact and possibly short out any high voltage components causing further damage. If you are not comfortable with working on or around high voltage circuits...please take it to a tech...it's not worth getting hurt. Good luck.
     
  4. tim boehlert

    tim boehlert Member

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    +1: I agree with Dave too - I haven't worked on one of these tanks, and I think I said above that it would probably be cheaper/less hassle just to replace the unit. In case I didn't mention it in this thread, DON'T use a soldering GUN, but rather a soldering iron - if you don't know the difference, have a tech do it for you.
     
  5. donnyjaguar

    donnyjaguar Member

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    That reverb spring is broken in the worst place. Not an easy fix for most.
    For this sort of repair I normally use a donor reverb tank for the parts. I'm guessing you don't have this so I'd suggest getting a new tank from Antique Electronic Supply as another has. The challenge would be to find the appropriate type. There is information on the web to help here. The fact the spring is broken tells me this amp has spent some time on the road! :) They don't bust sitting in a studio.
     
  6. Tone_Terrific

    Tone_Terrific Member

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    Solder the wire and clip the spring. It might be 'good enough' then, depending on your reverb need.
     
  7. Trego

    Trego Member

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    It has been on the road...stupidly laying down in my car instead of being propped up.

    I am going to buy a reverb unit...anyone know where to find out what I have?

    Is it on the reverb unit somewhere?
     
  8. Dave C

    Dave C Gold Supporting Member

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    The model number is usually inked on the outside of the tank...it may or may not also be on the internal plate which is what you have in your amp. I would certainly think Mesa could tell you which model. I suspect it's an R8AB2A1B which is available from AES.
    http://www.tubesandmore.com/
     
  9. JimmyR

    JimmyR Member

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    Just a bit off topic - but did anyone else think it was surprising that Mesa used carbon comp resistors in there??
     

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