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400+ smoked during recording today.

Discussion in 'Amps and Cabs [BG]' started by jimmyjames77, Feb 16, 2008.


  1. I was using my 400+s power section to record today and all of the sudden it started to smoke. I'm very bummed cause my guitar and bass amp went down 1 day apart.

    Anyway I opened the bottom of the 400+ up and what looks like a big resistor on one of the sockets is cracked in half and black. It is fried... ALL of the other smaller, what look like resistors, on that row of the tubes have a small black bubble in the middle of them. The rest of the big resistors in that row look fine. The other row of the tubes' resistors all look fine. Does anyone know what happened???:crying:
    Or can anyone give me ANY info on what could have happened?
    Thanks guys!
    Jim.
     
  2. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    Not sure exactly what happened - did you have the proper fuse in it?
     
  3. Maybe a tube shorted or something? Either way sounds like they started drawing way too much current, and have to double Benjamins "Did you have a proper fuse in it?"

    Also another question, im sure you did, but just to make sure, you did have a cab connected right?
     
  4. Lalabadie

    Lalabadie Guest

    Jan 11, 2007
    Overheating resistors are often because of shorts. That could be the tubes I've also seen pots making nice (horrific actually) shorts.

    At first I read the title and thought you smoked like 400 cigarettes in a recording session and would ask about possible consequences on your health.
     
  5. MarkMyWordsXx

    MarkMyWordsXx

    May 17, 2006
    im not a tube guy, but dont you need a dummy load if the head isnt running into cab at the proper ohms?
     
  6. anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    Bummer!
    I've directly input-ed my 400+ power section serveral times with no apparent issues.
    I cant help ya much on the serious tech stuff.

    I was just wondering if you had your effects-blend knob set to 10 or not, when you were inputting the effects return jack?
    (if it was set to a lower setting, you might have been running your master-knob/power section wide open to get much volume out of it...)

    Are you positive of your cab(s) ohm ratings and that they were all hooked up correctly?
     
  7. Mcrelly

    Mcrelly

    Jun 16, 2003
    Minnesota, USA
    were you running WITHOUT cabs or dummy load (POWER SOAK)?? I thought tube amp need an output for the speaker signal ALWAYS...
     
  8. MarkMyWordsXx

    MarkMyWordsXx

    May 17, 2006
    thanks i just said that lol
     
  9. Marley's Ghost

    Marley's Ghost Gold Supporting Member

    Feb 9, 2002
    Tampa, FL
    When I saw the thread title, the first thing that came to mind was that you were recording a Reggae album!
     
  10. peterbright

    peterbright

    Jan 23, 2007
    On The Bayou


    You read my mind.
     
  11. What was your recording setup? Can you post pics?
     
  12. Yes it did have the proper fuse in it. I believe it's an 8amp 250V slo blo fuse.
     
  13. Yes the cab was hooked.
    I had it set to 4ohms. Two 8 ohm cabs in series. I am using the 400+ as the power section to a guitar preamp. It smelled a little funny, I hoped it was the tubes, so to try and be safe I set my amp to the 2 ohm output. I had looked on the net and from what I was reading a lower ohm setting on the amp was safe for a higher load from the cabs. IE 4ohm load going into an amp set for 2ohm I'm not totally sure about that rule though. That's why I looked it up.
     
  14. Yes the blend knob was at 10.
    ANd I THOUGHT I was sure it was hooked up right. I've ran it the way I originally had it many times before. The way it was set when I first thought maybe something was straining.
     
  15. LOL :)My original title was going to be My 400+ smoked up today during recording. Then I read the title and thought that I'd get nothing but quips about the Gange in the thread.
     
  16. No pics but I'll try to describe.
    Guitar to Egnater preamp. Output from egnater preamp into effects return of 400+. Blend knob at 10. When it blew I had what I believe to be two 8ohm cabs in series making them a total 4ohm load. When she blew I had the 2 ohm output of the MESA running to my two guitar cabs(4ohm load). Originally when I thought something smelled a little funny I had the 400+ set for 4 ohms. Checked around the net and I thought that a lower ohm setting oon the head would be OK with a higher load on the cabs.
    ANy help is appreciated!
    thanks,
    Jim.
     
  17. Actually that's not good for a tube amp at all. You'd have been better with a 2 ohm load into the 4 ohm setting.

    Two eight ohm cabs in series, is 16 ohms. 16 ohm load in a 2 ohm tap - that's why your amp's dead.
     
  18. For your sake, I hope that your understanding of series is wrong, because if you did run two 8 ohm cabs in series, that's a 16 ohm load, and a VERY bad idea off of 4 ohm tap. Did you use a special cable or anything? What do you mean by "Two 8 ohm cabs in series"?

    That's even worse!

    Where did you look it up? That's wrong, and if you really had the cabs hooked up the way you describe, that goes a long way towards explaning why your amp is toasted.
     


  19. Hopefully my terminallogy is wrong. I'm saying "in Series" to describe the cabs Diasy-chained. IE Into the first cab then out of that first cab cabs parallel out into another 8 ohm cab. well I guess that's an easy way to remember series/parallel... "parallel out".


    So having 2-8ohm cabs wired parallel into my 4ohm tap on the 400+ should have been good right? Would running that setup into the 2ohm tap on the 400+ fry it?
     
  20. SO the rule is then always have your ohm setting on the amp set higher than the actual speaker load to be on the safe side? EDIT: Yes I know having both ohms the same number is best. I just meant if you didn't know the ohm load of two cabs. And yes, in the future I just wouldn't play then if I didn't know the load.


    [/QUOTE]Two eight ohm cabs in series, is 16 ohms. 16 ohm load in a 2 ohm tap - that's why your amp's dead.[/QUOTE]

    From what I'm reading here that is not how I had it set. I misspoke and said series instead of parallel.
     

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