WTF Smoke and all?

Discussion in 'Amps and Cabs' started by Red Planet, Aug 13, 2005.

  1. Red Planet

    Red Planet Member

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    Allright I'm at home by myself and I figure I'll go in the basement and do some playing.

    I have one 18 watt combo on and on standby and one 30 watt Tweed combo on standby and one Mesa Boogie Lonestar Classic on.

    The Lonestar is cranked with the master wide open and the drive knob allmost all the way and the channel gain allmost all the way and a freakin Boss Blues Driver on and I was Jamming like a fool. Amp set for 100 WATTS ss rectifier.

    So I had that little 1x12 combo Craked!

    The next thing I know there is a Major puff of smoke filling the room. WTF!

    I'm pretty shure it came from the LS only because it was cranked so I shut every amp off and did some looking, I couldnt find anything on any amp hot except Tubes. Checked speakers, trannies,etc...

    Turned each amp on and tried them with no problems. Tried the Lonestar again cranked and had no problems. Played it for a while like that with no problems.

    Again WTF?

    Its clear it was an eletricall smell and when I came upstairs smelled it all over the house. What gives?

    When I first noticed it was when it bellowed (visually) over my head. Then I smelled it. :confused:

    Whats going on here?
     
  2. LSchefman

    LSchefman Member

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    Maybe it was something in your house that had nothing to do with the amps? Did you check your fuses, etc?
     
  3. r9player

    r9player Silver Supporting Member

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    Since you were cranking it and jamming away so hard .. maybe your fingers got on fire and you started smoking away ...

    Besides that maybe something hit the tubes or a circuit and went up in smoke?
     
  4. bluesdoc

    bluesdoc Gold Supporting Member Gold Supporting Member

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    What did you eat for dinner? :eek: :D

    jon
     
  5. Red Planet

    Red Planet Member

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    I'll try some sniffing today. I was plugged into a 10 outlet surge proctector strip with ground.

    It was not something in the house. It came out of that amp. I have my amps setting in the corner of my Studio and the smoke just bellowed up out of the corner as I was playing. It was definate an electrical burning smell.

    Since I was cranking it could it have been something in the speaker getting to hot? But it didnt feel hot.

    I've had this amp for Several months but I've never cranked it like that. The loudest I've had it is 100 watts SS Rectifier on the clean channel and 50 watts Tube Rectifier on the dirty channel with the master about 11:00 for dirty rythem and the solo master about 1:00 for solos.

    I was feeling like blowing the walls down last night and turned it up. As I said I looked at everything off and couldnt find anything then turned back on and played longer with no problems.:confused:
     
  6. Red Planet

    Red Planet Member

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    Well cant I check the Speaker Impedance?

    Yeah I shouldnt have been cranking it like that. :NUTS
     
  7. fullerplast

    fullerplast Senior Member

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    Running flat out like that you are really cooking your output tranny, basically putting a square wave into it. It's possible the smoke you saw was either from whatever coating is on the laminations, or from the windings and/or interlayer insulation. This is the same sort of thing people running attenuators need to be careful with.
     
  8. Red Planet

    Red Planet Member

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    Wouldnt it have been hot to the touch?

    It was cool as a cucumber.

    Well I shouldnt have done that I know but its under warranty.:D
     
  9. VaughnC

    VaughnC Supporting Member

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    With all 4 output tubes cooking in the 100 watt setting, you may have burned out one of the output tubes screen resistors. If that's the case, the affected tube would shut down and, because there's another tube available to reproduce that side of the output signal, you may not have noticed any difference in the sound.

    Suggestion: if you have a bias meter, check all 4 output tubes to make sure they are all conducting properly.

    Otherwise, a visual inspection of the inside of the chassis might set your mind at ease....if you see no obvious signs of overheating or burning inside.
     
  10. Red Planet

    Red Planet Member

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    OK I'll give it a look and see if something is smoked.
     
  11. Red Planet

    Red Planet Member

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    Well after thinking about it. Its still under warranty. I probably shouldnt pull the chasis. I should take it in to Bakos and have him look at it. He is a Boogie warranty repair center. I"ll play it some more and see if I can tell is it putting out 100watts in 100 watt mode. Its easy to switch between 50 and 100 watts while playing.

    Look at the tubes with it on.

    Any other checks I can peform without pulling the chassis? I have a Fluke Digital 1,000 volt - volt meter.
     
  12. John Phillips

    John Phillips Member

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    Meter the speaker. It should be between 6 and 7 ohms DC.

    Vaughn is also right - it could be a blown screen resistor. Watch all four power tubes carefully when you flip from standby to on with it in the 100W mode. All four tubes should brighten, change color or flash slightly, at the same time. If one doesn't, you've almost certainly got a blown resistor on that socket. You can check for sure if you pull the tube and meter the voltage on the pin contacts, but BE CAREFUL - the full B+ is present on both the plate and screen connections (pins 3 and 4 - if there's voltage on pin 6 it's being used as a connection point).


    BTW, IMO you absolutely should be able to totally crank an amp pretty much indefinitely without any damage occuring other than increased tube wear - either into the stock speaker, without it blowing, or into an attenuator. If you can't, the amp isn't properly designed or built IMO.

    I test all amps which I've repaired like that (not with a pedal, admittedly - although it shouldn't really increase the power output above what the amp is capable of on its own), FWIW... dime every knob and play it into a dummy load for at least five minutes continuously. That's one reason I don't get too many amps back for re-repair - it tends to weed out the ones with problems. And before anyone asks - no, I've never blown a transformer on any amp (including vintage ones) like that, and if one ever does fail I won't feel especially guilty about it since it was obviously not up to the job anyway...
     
  13. fullerplast

    fullerplast Senior Member

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    While I tend to agree with you in theory, there are reputable amp builders and transformer manufacturers that would disagree with you. There are vintage amps that would be pretty marginal in that area as well. Sometimes the size of the OT is what makes the tone, at the expense of handling absolute maximum ratings for 5 mins straight. Same with speakers....you can select a speaker that would never blow but you may not end up with the best tone. It's kind of like tires on a car-you don't need to have tires rated for the max speed of the car if you never drive that fast. I suspect many amps were not designed with flat out operation as the number one criteria, certainly not vintage amps. The same reasoning applies to the common practice of exceeding tube max ratings. Many rules are "bent" with respect to amp design in the interest of tone and/or cost considerations.

    Personally, I think you should warn vintage amp owners that you like to perform that test.....:eek: (especially old Marshalls!)
     
  14. John Phillips

    John Phillips Member

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    I don't advertise (or deny) the fact that I test amps like that because there is no need - it's normal procedure to test something fully IMO, and people seem to come to me because they want amps to be fixed so they stay that way. If the amp was a true museum piece I might think about not doing it. If it's a working amp it gets tested like that or I won't work on it, because I can't and won't guarantee the repair otherwise... brutal perhaps, but effective. Either an amp is up to the job or it's not.

    The same with speakers - you don't have to blow them in order to make them sound good IMO. I would never recommend using a speaker that can't take the full output of the amp, and I think Mesa should not have fitted a 100W amp with a single 90W speaker.

    For the avoidance of doubt, I've tested hundreds of vintage amps, mostly Marshalls, like that and never blown one single OT (or any other major part). I've never felt there was even a serious risk - what kills OTs is not sustained high-power operation, it's running into an open-circuit - especially a momentary one... just like the kind you get from an faulty impedance selector or a bad speaker cable, which is IMO the true reason old Marshalls appear to suffer more blown transformers than other brands. Heads are more subject to this than combos, amps with no shorting switch in the jack more than ones with it... and especially those which use appallingly unreliable cheap pull-out selectors and fit them so they get knocked when the amp is bumped against something, or get set wrong by musicians. Sound familiar? ;)
     
  15. Red Planet

    Red Planet Member

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    OK I looked at the power tubes. They all four flash when in 100 watt mode and the standby is flipped. If I set it to 50 watts only two of em flash.

    I ohmed the speaker and got 7.6 ohms.

    With my head in the back of the amp and a bad cold I can still smell that burnt electricall smell in the back of the amp strong.

    Gonna take the back board off and sniff around see if I can find where its coming from (speaker or amp?).

    Anymore suggestions?
     
  16. Red Planet

    Red Planet Member

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    Did some sniffing and cant tell. I looked in the manual just be shure and it says nothing about not cranking the amp.

    Even says you can mismatch the impedance without hurting the amp.
     
  17. Red Planet

    Red Planet Member

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    Gonna hook it up again in a minute and play it for a while see if I can tell any problems.
     
  18. fullerplast

    fullerplast Senior Member

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    Just different philosophies.... If I brought my car in to have the plugs changed I wouldn't expect the mechanic to test drive it at 100mph. Likewise, if I brought my amp in to have the filter caps changed, I wouldn't expect it to be played full bore into an attenuator for 5 minutes. As long as your customers know this, no harm, no foul. :cool:

    As for speakers, something like Blues and AC30's belong together even if they fail a worst case analysis. Such is the case with many aspects of amps. We sometimes live on the edge in the pursuit of tone;) . Bulletproof amps designed for the absolute worst case conditions in all aspects (including tube operating points and speakers) can sometimes sound tight and lifeless at typical operating conditions IMHO. Just like an old acoustic guitar with a thin top and light bracing-it sounds like a cannon but won't stand the abuse of a plywood guitar that sounds constipated but can be hit with a hammer.
     
  19. fullerplast

    fullerplast Senior Member

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    You say you felt the OT just after the amp was smoking and it was cool to the touch?
     
  20. riverastoasters

    riverastoasters Member

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    Completely agree.
     

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