Paul Marossy Posted August 20, 2005 Report Share Posted August 20, 2005 (edited) This has got to be the world's easiest tube amp repair ever! A friend of mine has a Mesa Boogie Nomad 45. It is a three channel amp and it was having trouble switching ever since he had it. It couldn't make up it's mind when you wanted to switch between channels 1 & 2 - the relay would just flip back and forth and try to switch between one channel or the other, never really switching as intended. My intuition told me to start with the footswitch itself. I took it apart and took a look at the PCB. The first thing that I noticed is that there was a large amount of flux around all five of the connections at the LEDs. I got some alcohol and cleaned off the excess flux from the entire board. Then I turned the amp on and gave it a try, and now it switches perfectly! It seems really weird that this could cause a problem like that, but this isn't the first time I have encountered this phenomonon where excess flux has caused a problem like this. Go figure. Edited August 20, 2005 by Paul Marossy Quote Link to comment Share on other sites More sharing options...
Southpa Posted August 20, 2005 Report Share Posted August 20, 2005 (edited) Just another unit that got past quality control at the factory. I guess they can't check EVERY one. Thats why I keep my eyes open for things that people say "doesn't work". Sometimes its so simple its mind boggling and folks don't even bother to figure out why. Edited August 20, 2005 by Southpa Quote Link to comment Share on other sites More sharing options...
unclej Posted August 20, 2005 Report Share Posted August 20, 2005 good catch..and you didn't even have to change the power tubes to get more gain or anything. Quote Link to comment Share on other sites More sharing options...
MerlinTheWizard Posted August 20, 2005 Report Share Posted August 20, 2005 Kind of weird... flux isn't supposed to be conductive, so its presence in itself should not pose that kind of problems. Although older solder flux may become slightly conductive over time... One thing is that it's always better to clean flux after soldering, because it may cause corrosion... surprising that such a renowned brand of amps would not do that... Quote Link to comment Share on other sites More sharing options...
crafty Posted August 20, 2005 Report Share Posted August 20, 2005 Kind of weird... flux isn't supposed to be conductive Flux itself is not conductive, but if left to "dry" then contaminants that are conductive can stick to it and create shorts. I'd bet that the footswitch was probably something they outsourced to someone else and was never really tested with the amp during the final checkout. Quote Link to comment Share on other sites More sharing options...
Saber Posted August 20, 2005 Report Share Posted August 20, 2005 (edited) That IS weird if all you cleaned off was flux. There may actually be a bad (or cracked) solder joint somewhere in there, and some of that flux was between the joined parts. Cleaning off the flux may have allowed the badly joined parts to touch to complete the necessary connection. If that's the case, oxydation will occur in the joint and the problem will return. Only time will tell. Edited August 20, 2005 by Saber Quote Link to comment Share on other sites More sharing options...
Paul Marossy Posted August 21, 2005 Author Report Share Posted August 21, 2005 That IS weird if all you cleaned off was flux. There may actually be a bad (or cracked) solder joint somewhere in there, and some of that flux was between the joined parts. Cleaning off the flux may have allowed the badly joined parts to touch to complete the necessary connection. If that's the case, oxydation will occur in the joint and the problem will return. Only time will tell. I looked at all of the solder joints real carefully. Everything looks pretty solid. I have been told that "Most flux is hydrophillic. After some time and exposure the flux can become conductive." That could explain a few things... Quote Link to comment Share on other sites More sharing options...
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