THE HOWLING (JCM 800 2210 )

Discussion in 'The Workbench' started by Exotic, Nov 11, 2019.

  1. Exotic

    Exotic Active Member

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    what r some reasons why a marshall jcm 800 2210 would howl when u turn the guitar off ,and sometimes the sound shows up sometimes it doesn't ,says the tech . but as for me ? the reverb knob was acting funny affecting the volume of the amp with the master on 0 . and when u switch the guitar off it howls ,what causes this? he is going to keep on looking .
     
  2. ampmadscientist

    ampmadscientist Well-Known Member

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    If you take out V1 preamp tube (tube closest to the input jack) does the noise stop?

    Are you able to check or re-solder the input jack for possible cracked connections?
     
  3. ampmadscientist

    ampmadscientist Well-Known Member

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    Howling:
    possibly the primary of the output transformer is reverse wired.
    We don't have enough information, and pictures will help probably.
    I asked you: if you take out the V1 preamp tube does the noise stop?
    We need answers to solve a problem.
     
  4. Exotic

    Exotic Active Member

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    yes i will ask him to take that tube out and see what happens
    and he is going to check for cracked solder connections
    keep in mind this is a set of 9 brand new jj tubes
     
  5. RLW59

    RLW59 Well-Known Member

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    "Switch the guitar off"

    So your guitar has a kill switch? Or do you mean you turn the guitar's volume knob down all the way? Or are you unplugging it? (If so, are you unplugging from the guitar with the cable still plugged into the amp, or pulling the plug out of the amp?)

    And the amp only howls when the "guitar is switched off"?

    Does the howl start up softly and get louder? Or does it scream as soon as you "turn off the guitar"?

    Is it a shrill high pitched whistle? Or more of a high pitched hum?

    (Wondering if this part of the problem could be the guitar instead of the amp?)

    Are you saying the amp volume changes as you turn the reverb knob? Or are you saying the reverb effect goes down as you turn the knob up, then starts going back up as you turn the knob even higher?

    If you have a footswitch, what happens when you turn the reverb off?

    Since you don't have the amp with you to check any of the things people suggest you check, the only way anyone can diagnose it is based on your description of the problems.

    So you need to give us clear descriptions of exactly what was happening before you took it to the tech.
     
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  6. ampmadscientist

    ampmadscientist Well-Known Member

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    It did the same thing before you changed the tubes?
     
  7. RLW59

    RLW59 Well-Known Member

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    A few weeks ago Exotic was posting a lot of questions about his newly purchased JBLs. I'm under the impression the amp was healthy at that point (he's mentioned that he was wondering if an impedance mismatch or similar while he was swapping speakers might have caused the problems).

    Not clear when he retubed it.
     
  8. ampmadscientist

    ampmadscientist Well-Known Member

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    Once in my whole life, I have seen a bad power tube cause this type of noise.
    I think it is possible that he has one bad power tube.
    I have seen a reversed OT primary cause this type noise also, and this is a more common miswire in amplifiers.
     
  9. Exotic

    Exotic Active Member

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    wow thanks guys ,yeah so the tech has the amp,i told him to replace the left volume pot ,(the master volume) . and the reverb pot . to take out the v1 preamp tube ,and see what happens ,to check solder connections ,to check resistance on the reverb pan . the trouble is the tech and i have had different experiences with the amp probably due to the fact that we run differently . he is a no distortion guy ,i'm a crunch guy . he said the amp was acting normal this morning ,which is really wierd ,cuz he wants it to howl to find what the problem is . quick history ,i got it non working ,i took it in he replaced a power switch a small transistor or whatever those are and a couple power tubes ,cleaned the pots and it came back to life . 10 months later it lost power and distortion so it got 9 new tubes . now after i had done my cabs from one day to the next i turned it on and what i experienced was this , it sounded too high even with master at 0 ,i use gain and volume on 10 to get overdrive . i fiddled with the reverb and the volume of the amp changed from high to lower as i turned the reverb knob ,when i switched the guitar off with my toggle switch the one where u switch pickups ,i use the neck pickup off . that's when i heard the howl ,a squeal . so this happened a couple times turning the amp on and off and i said this is wack i gotta take it to the tech .
    if he can't make it work right i'm taking it back after like a month or two and taking it to sam ash .
    i told him to forget about the tubes being new . and to check them .
    we agree it has nothing to do with me and my cabs because all 3 cabs are showing good readings on 2 different dmm's
    it's an immediate high pitched hum i guess .
    i have to look for a foot switch but i don't remember if it is for that amp , might be for a valvestate
    it did do the same thing after the tube change but he insists this time it's a different howl!
     
    Last edited: Nov 13, 2019
  10. RLW59

    RLW59 Well-Known Member

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    Well. Ummmm.

    Other than telling the tech the symptoms/problems and the conditions when the problems occur, you shouldn't have to suggest any of these possibilities.

    He should know all this stuff, and more. He should be telling you what he's going to test, and why he's going to test it.

    If you told him you dime the gain and volume and turn the master way down, he should test it like that when trying to provoke the problems. Not clean, just because he prefers clean.

    A healthy 2210 is a great amp. I don't think it makes sense to sell it off unfixed, at a huge discount.

    From the history of work that tech has done on that amp, it sounds like he's maybe not the greatest tech in the world?
     
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  11. Exotic

    Exotic Active Member

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    yes i know you're right but in the past like 30 or 40 years ago he did work for rock stars (dokken guns and roses etc for starters )his shop is plastered with gold and platinum records they gave him in appreciation . it's just that he is becoming very elderly ,so i will try to give him some more ideas and wait a bit and see how it goes ,if him and i give up i will take it to sam ash a large local music store in the area ,but that is 6-8 weeks and probably much more expensive . in lots of local yelps people say he is the best and don't go to anyone else .
     
  12. ampmadscientist

    ampmadscientist Well-Known Member

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    it's an immediate high pitched hum i guess .

    That "is" high frequency oscillation.
     
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  13. NewReligion

    NewReligion Well-Known Member VIP Member

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    Yes I hate to state the obvious but it sounds as if this tech may cause you more problems than resolutions.

    I played Marshall JCM 800 2210/2205 for more than a quarter century. Killer stock Marshall circuit especially with a SD-1 in front of it. I used the later circuit revised 1986-1989.

    It has an Effects Loop. Tech should’ve pulled the power tubes out plugged into the preamp section of the amplifier ran the send out to the return of another amplifier. And then reverse the process this way he knows if the problem lies in the power or preamp section.

    This cuts the workload in half. Time for a new tech in my opinion my friend. I don’t understand why you’re going through and replacing potentiometers without reason?

    David

    Below is the only kind of howling we should get from a 2205/2210. Recorded about 2009/10

     
    Last edited: Nov 15, 2019

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