JCM 900 reliability issues?

Discussion in 'Marshall Amps' started by seeker88, Feb 21, 2015.

  1. V-Type

    V-Type Active Member

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    ^
    Im not sure the benefits out weigh the stress put on the components myself.
    Btw I blew a board years ago from an accidental miss match(BV120h).
    Pass.
     
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  2. ampmadscientist

    ampmadscientist Well-Known Member

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    There are certain design defects in some Marshall amps.
    Read This:
    Marshall JCM2000 Stable Bias Mod

    We know what the defect is, and how to fix it.

    There is no perfect design, it's all a compromise.
     
  3. ampmadscientist

    ampmadscientist Well-Known Member

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    The trick to the effects loop:

    The first effect pedal in the loop must have an input level volume control.
    The last pedal in the loop must have an output level volume control.

    Don't depend on the Marshall effects loop to give you the correct levels.
    You must dial them yourself, on the effects pedals.

    Effects Power:
    An isolated professional effects power supply is highly recommended to prevent hum and ground loops.
    This is more important than many realize.
     
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  4. sccloser

    sccloser Well-Known Member

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    I have a JCM 900 2500 mk III. I got it used, gigged it pretty regular for about 2 years, and now less often as I am using smaller amps in the smaller venues. I only had 1 issue since I have been playing it. I was at a gig and during the last set I started to notice that my volume was fading out then coming back. It was getting worse as the set progressed but I managed to finish out with it. When I got it home, I noticed the tubes would light, then go out. I opened it up and started checking and I found a bad solder joint on the tube heaters...the first in series from the tranny. Touched it with a hot soldering iron and it was fixed. No other problems.

    I often choose it over my jcm 800 because the taper on the master volume pot makes it much easier to adjust the volume to the venue. Plus, I like the dual master vols on this amp.

    Anyway, as far as reliability, I would have no issue using any 900. I have had friends with them, one who is notorious for not taking care of his stuff, and his 900 never failed, though he had plenty of other amps that did not hold up. He was rough on his stuff.
     
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  5. pleximaster

    pleximaster Well-Known Member

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    I always thought the 900 were very reliable and trusty there are other amps that are worse in that department...

    plexi
     
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  6. Landshark

    Landshark Well-Known Member

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    From youtube videos I had watched, the tones you could coax out of the 900 line were very pleasing, which was the icing on the cake as I had heard of their reliability. I had just gotten out of a bad relationship with an unreliable amp from the 2000 line. I needed some stability.
     
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  7. Ghostman

    Ghostman Well-Known Member

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    Buy a 900. If it breaks on you, then there's an issue.

    If it doesn't break on you, then it doesn't have an issue.

    Glad I could help. :wave:
     
  8. Tea41

    Tea41 New Member

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    I've had a JCM900 4502 for 25 years, never had an issue, always fires up and sounds great. The thing IS A TANK.
     
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  9. charveldan

    charveldan Well-Known Member

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    [​IMG]

    [​IMG]


    If its on the internet it must be true but i still have none of these problems ...
     
  10. stalefish

    stalefish Well-Known Member

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    You are not the benchmark for anything except bitter loneliness. The problems with DSLs are common and well documented....and easily fixable.


    Like everyone else, I also believe the 900s to be quite bullet-proof. Tone subjectivity aside, one thing that's pretty much certain is that the 900 series is probably one of Marshalls more reliable models, even as they age today.
     
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  11. RobS

    RobS Active Member

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    Ive had mine since the early 90's (6l6 model) and never had a major issue. Had an output valve fail a couple of times and trigger the valve fail led & pop the fuse however its always through a powerbrake pretty much with the vol up around 8 on both channels. gets hot but just keeps going.
    Extremely quiet amp as well when cranked.
     
  12. Clammy

    Clammy Well-Known Member

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    My first tube amp was a JCM900 100W Dual Reverb (model 4100 with EL34s). I bought it brand new in 1990, and ran it into 2 JCM900 4x12 cabs (1960A and B) for over 7 years. I rehearsed 3 times/week at gig volume (LOUD), gigged it regularly, recorded with it, and that rig even served as my first bass rig, when I made the switch to bass in '97. Never had a problem with it in all the time I owned it.

    Cheers!
    :hbang::hbang::hbang:
     
  13. shane159

    shane159 Member

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    :applause: You always have the answers Dan.:ugh:
     
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  14. Rahlstin

    Rahlstin Well-Known Member

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    1990 JCM900 4500DR - Bought new in 1990 sold off in 2005 did hundreds n hundreds of shows. Never ever an issue. My only disappointment was the Diode clipping and the bottom end was a bit weak. re diode clipping I could have bought an 800 and just used a pedal... but it worked pretty good until I got my DSL100 in 2005.
     
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  15. Roadburn

    Roadburn New Member

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    Thank you very much for this link.
    Bookmarked it.

    My H&K TM18H says 8-16 Ohm on the back.
    I always wondered how and why they would put it there if it could damage the amp.


    Impedance mismatch is one of the biggest mysteries in amplifier/guitar land.
    This will divide camps a bit more (or not)
     
  16. iron broadsword

    iron broadsword Well-Known Member

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    Np. Idk how okay it really is and all that.. IMHO an EQ in the loop is safer and more versatile anyways.
     
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  17. Blacque Jacque

    Blacque Jacque Well-Known Member

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    Mismatches will stress all the components more than the ideal situation.

    Obvious things like more power dissipated by the OT mean it will heat up more. Same with the tubes, the reflected power from the transformer mismatch will end up getting dissipated in the tubes. Run it flat out into a mismatch & you could be in for trouble. It could easily redplate if it's biased hot.
     
  18. geddyleefan

    geddyleefan Active Member

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    JCM 900s are excellent amps, never a problem with my '90 4102 and its 25 years old.
     
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  19. geddyleefan

    geddyleefan Active Member

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    actually the 2000s are fine amps too it was the infamous TSL122 combo with that bias drift problem but other than that I still prefer the 2000s over the new DSLs
     
  20. ampmadscientist

    ampmadscientist Well-Known Member

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    "the most unreliable Marshall ever made..."

    Whoever said that is an idiot.

    People who complain about the amp being unreliable, are usually abusing it.
    Marshall amps, 900s, are pretty well made.

    But when the amp is connected and used wrong, expect problems.
    Problems are almost always operator caused.

    I fix amps, but I can't fix stupidity.

    Out of 100 people there is always 1-2 moronic thick headed idiots - who abuse equipment on a daily basis.
    A. the guy who spills beer in the amp...
    B. The guy who hooks up the 2.4 ohm $29 attenuator...
    C. The guy who uses broken defect effects pedals, and blames the amp for the hum and noise...
     
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