What did I do to my Marshall?

Discussion in 'Amps and Cabs' started by Motherfuzzer, Mar 19, 2008.

  1. Motherfuzzer

    Motherfuzzer Supporting Member

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    It's a 1987x reissue. A few years old. I haven't played it much lately, and I use a Hot Plate. It probably hadn't even been turned on in a few weeks. SO, I turned it on, got plugged in, started playing, turned it up, and then nothing. I smelled something, the el34's were glowing orange.
    I brought it to the repair shop, and it's been three weeks now ,and he keeps telling me he hasn't figured out whats wrong with it yet.
    Any ideas?

    Thanks guys.
     
  2. jezzzz2003

    jezzzz2003 Member

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    Id say its a screen grid resistor or a bad tube, probarbly just needs the fuse and tubes replaced and a rebias to stop the redplating, it really shouldnt be that hard.
     
  3. jowe

    jowe Member

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    I had the el34's in my jcm 900 glow bright red on the entire face of the inner plate , and the problem turned out to be a bad preamp.

    Goodluck with your amp man!
     
  4. StompBoxBlues

    StompBoxBlues Member

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    Can I just ask...is that really your question, or is it how to find out if the guy is really working on it?

    I ask because diagnosing a problem from symptoms over the net is really iffy (though folk can suggest known problems that would show those symptoms, like the screen grid resistor), compared to a guy that presumably knows amps, sitting in front of it...

    But three weeks? Even if he hasn't figured out what's wrong with it yet, you ought to ask how much time he has put in already (ask nicely of course, but I am betting you pay hourly rate?) and ask specifically if he can tell you what it ISN'T....which he should be able to do, saying "well, I checked the bias and it's okay, checked the screen grid resistor and it is okay, the tubes check out, etc., etc.".

    I mean, it shouldn't be insulting to a business man or mechanic, or anyone...especially if they are professional and after three weeks are just saying "I haven't figured out what it is yet". You deserve a little more info than that. Is it still having the problem on his workbench?
    Even a doctor, imagine having a sickness and the doctor just shrugs and says "I still can't figure it out...hmm..", they don't do that, they tell you (even though you yourself are not a doctor) in laymens terms what has been tried, what results were, what they want to try next.
    An amp is a lot simpler than the human body....even PTP. Seriously, you pay for his time to diagnose, he ought to be able to spend 5 minutes on the phone telling you what has been tried and why, and what he thinks he can next try.


    Is this person reputable? I think it all hinges on how many hours he's been working on it. Amps shouldn't be that hard to diagnose when you know that the problem is in the power amp or power section.

    You need more information from the guy, write it down, then post that here so folks know what has been tried, it might be that someone here can suggest something he's not tried.
     
  5. KazJY

    KazJY Member

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    yeah, three weeks is a long time for a diagnosis.

    I had a similar thing happen to me (the sound level dropped by half, along with the glowing hot tubes) - my tech thought it was a bad tube, or that the amp went out of bias - I swapped them around, and I haven't had that problem again - he thought one of the pins might not have been firing correctly, and I might've fixed it by swapping them around.
     
  6. StompBoxBlues

    StompBoxBlues Member

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    It's okay, I mean folk can do what they want, but I really get dissapointed when we try and help out on somethign ongoing like troubleshooting, or a problem with whatever...and never end up hearing what is going on or what was found out.

    So, how did it go? Any news yet? Has the guy found the problem and if so what was it...if not...what's he done to it to troubleshoot?
     

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