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Walkabout speaker coil (correct terminology?) issue.

Discussion in 'Amps and Cabs [BG]' started by HarveySpaceBass, Aug 15, 2019 at 3:38 PM.


  1. HarveySpaceBass

    HarveySpaceBass

    Sep 24, 2007
    Hey there, TB brothers. Just wondering if anyone else has had this issue with their Walkabout? This is the third time this solder point has come loose.
    60595631_10217564585860426_8134338437063901184_n.
    The first time it happened was about three years ago. I thought I had blown the head so it just sat there for awhile. I had purchased a D800+ so I was just using that. I was getting ready to finally take it to a shop because I really missed this amp. But I figured I would open it up just to see if it was something stupid. And low and behold, it was what I thought to be a simple solder job. The first time I re-soldered it, I used lead free solder. Which was why I thought it came loose again about 3 weeks later. The second time, I used the proper 60/40 resin core solder. Although it lasted much longer (about 2 months) it came loose again last night during a gig. The good thing is that it only impacts the speaker outputs so I was able to continue using the direct out. I only needed to add a little bass to my monitor. I guess my solder skills are to be desired. I am taking it to a shop this time but was wondering if anyone has seen this. Or, if @agedhorse had any perspective on this particular issue? Thanks in advance!
     
    Last edited: Aug 16, 2019 at 10:59 AM
  2. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Your picture is invisible.

    I'm not familiar with this problem, but once I see your picture I can compare it with the benchmark unit I have here.

    The reason I want to see the picture is because there are a lot of techs that attempt repairs (or modifications) and end up causing problems, so I want to be sure I get you accurate information.
     
  3. two fingers

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

    Feb 7, 2005
    Eastern NC USA
    Wanna just forget about it? Send it to Mesa. Let them go through it. Turnaround time, price, and customer service are all top notch. I sent mine to them a couple years ago amd now I just don't worry about it.

    They will go through it top to bottom amd front to back. Any updates will be done. Anything they find will be fixed. And they'll shoot you emails or actual phone calls along the way.

    With that kind of unknown issue, that's what I would do.
     
    S-Bigbottom and agedhorse like this.
  4. I had a shirt that was really crummy...I had to sew the same button back on three times!

    Lead/tin resin-core solder is the correct thing, of course, but if you used something else first, you may need to expend some effort to completely remove all the old 'solder'. I would definitely try to clean up the joint before trying to re-solder it. But if that's all that's wrong, I don't see any need to return it to the factory to be serviced...pretty much any decent tech should be able to fix it, unless you've done some real damage in your repair attempts.
     
    RSBBass likes this.
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Once additional damage has been caused, generally the cost of repair goes up considerably.
     
    Redbrangus likes this.
  6. HarveySpaceBass

    HarveySpaceBass

    Sep 24, 2007
    Thanks for the replies. Not sure why the pic disappeared. I just re-added it. I don't think this is anything that requires being shipped to Mesa. I plan on just taking it to a local authorized repair shop. There is no "damage" so to speak. Just a solder point that won't stay put. This amp has seen a lot of action in the 9 years since I got it. In fact, 9 years today coincidentally. When soldered, the amp works fine. The amp does not get overly hot or anything like that either. Besides, if the amp was getting hot enough to melt solder, this thing would be dead by now. 60595631_10217564585860426_8134338437063901184_n.
     
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    As I thought, it looks like your unit has an incorrect part that does not appear to be a factory part as there is no mention of it ever being installed on the revision history. This part should be replaced by a wire jumper. Do not change anything else.

    I mentioned the after-market modifications because sometimes a tech in the field will think that something they might have seen in another type of amp or something they read on a tech forum was a good idea without understanding what the part does and why it's used. I have seen this before, where a tech sees a part like this (as used correctly on the Carbines) and assumes that the Walkabout will benefit without understanding that the power amp topology is COMPLETELY different. L1 on the Walkabout corresponds to a wire jumper in the parts list.

    I'm going to go off a bit on (some) techs because I am seeing more and more damage and problems caused by techs who attempt to repair something that they do not completely understand. Then, there's the techs who make the majority of their income by modifying an otherwise perfectly fine and functioning circuit, causing other problems. For example, with all Genz Benz products that come in for the factory service program, it's standard procedure to remove all unauthorized modifications and return the unit to original factory specs. This way I can confidently provide a 90 day warranty to the repair and it greatly reduces failures down the road.

    If a tech feels compelled to modify everything they touch, IMO they need to much better understand the bigger picture consequences of their actions and the potential impact on the future reliability of the amp. This is especially true of vintage products, where it seems that some techs feel the need to put their "signature" on every amp they touch.

    This is what it's supposed to look like (even if you have an older board revision):
    IMG_1731[1].JPG
    [edit for clarity]
     
    Last edited: Aug 16, 2019 at 1:10 PM
  8. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    A tech installed a coil where a jumper is supposed to be? Wow!
     
  9. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I've seen it before, a tech believes, or read on a forum, or "summoned the spirits" to determine that the factory left off a part and installed it because there was what appeared to be a place for it on the PCB without knowing the facts.
     
  10. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    I wonder if was acting as a LPF and messing up his tone, in addition to creating all that heat that was melting the solder?
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    No the inductance is way too low, especially compared with the Zout. It wouldn't have gotten more than a degree above ambient. It looks like it was soldered to the top of the board and not even through the PCB holes.
     
  12. HarveySpaceBass

    HarveySpaceBass

    Sep 24, 2007
    I hate to be the bearer of bad news, but this amp has only been serviced once and it was at Mesa Boogie. If this is an incorrect part, it was done by Mesa Boogie. This unit had a faulty fan that many Walkabouts originally had. About 3 years after owning it, the fan died during a gig. I had no idea until the amp completely shut down. And by that time, the damage had been done. The amp was fried. Seeing it was still under warranty, I sent it to Mesa. From what I remember, they upgraded the fan and had to replace all the MOSFETS as well as some other components. This is disheartening to say the least.
     
    Last edited: Aug 16, 2019 at 12:47 PM
  13. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    On an older amp there's obviously no way of knowing what may have happened, and may have in fact been included in some early builds (the amp goes back almost 20 years). I have the "complete" revision history and while it shows a legacy part location, none of the service/support paperwork I have shows it as being used or what the value was. It won't hurt anything if it is used as long as it's securely attached.

    The proper fix is to remove the part and replace with the factory approved jumper.

    Here's a picture of what looks a very early revision I have seen myself, and there's no choke used:
    [​IMG]
     
    Last edited: Aug 16, 2019 at 1:53 PM
    HarveySpaceBass likes this.
  14. HarveySpaceBass

    HarveySpaceBass

    Sep 24, 2007
    This is a blackface from 2010. I never opened it before that first problem so not sure if this was in there prior to that. I am guessing that an authorized tech near me can just order this part from Mesa and replace it? Seems silly to pay for the shipping across the country and back (I am in Boston area) for such a small repair.

    6 gigs in 10 days coming up. Guess I will be rocking my D-800+ and 15" Powerhouse cab for the next few weeks. Which isn't a bad thing.

    Thanks again for the info and your time, @agedhorse. Much appreciated. It is really great having you on this board.
     
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    No, they do not need to replace the part, there is no part to replace. They need to simply remove that part and install the jumper as shown on the photo I posted in post #7. This is a unit that came off the assembly line maybe 4 or 5 years ago and was current production through end of life.
     
  16. HarveySpaceBass

    HarveySpaceBass

    Sep 24, 2007
    Yes, I meant order the jumper and replace the coil with it. Sorry for not stating that clearly. I am guessing they will know this, but for my own knowledge, is this jumper a standard part? Or, is this something that should be ordered directly from Mesa?
     
  17. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, ChopShopAmps
    Slightish derail ...
    @agedhorse if you were to guess, what would be the "advantage" of this inductor that someone felt it offered over the jumper; or what would you speculate was it meant to "fix"?
     
    HarveySpaceBass likes this.
  18. Since @agedhorse has shown exceptional patience up until now, I'm going to field this one: it is not a 'part' at all...it's just a short piece of wire that jumpers two pads on the PCB together. The tech will know what to do, but it isn't a part that can be ordered.
     
    agedhorse and Coolhandjjl like this.
  19. Coolhandjjl

    Coolhandjjl Supporting Member

    Oct 13, 2010
    Appleton
    Jumpers can be made out of stuff in any tech’s parts bins. I usually look for a component that has long leads the same thickness as what I need and merely clip off a piece.
     
    HarveySpaceBass likes this.
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I can't think of any practical advantage with this amp's specific topology, and I can't think of anything it would fix either.

    There are other power amp topologies where is may be an essential part of the amp's global feedback stability under capacitive loading conditions which do not apply to this amp as I have stability tested it without the choke and it easily passed.
     
    basscooker likes this.

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