Quick 900 Dr Question

Discussion in 'Marshall Amps' started by BrentD, Sep 16, 2017.

  1. BrentD

    BrentD Active Member

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    I just picked up a 900 DR off of craigslist. The reverb doesn't seem to be working but I don't have a footswitch attached. Is the reverb defaulted to "off" without a footswitch, or should I be investigating a problem?
     
  2. Zaphod Beeblebrox

    Zaphod Beeblebrox New Member

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    On mine - a '95 50 watter - it's default is "on" without the footswitch attached. I'm not 100% sure but I think the reverb shares a valve (the middle ECC83) with the effects loop. Have you tried that? It could be a broken spring or dodgy tank connection somewhere, or something else entirely but good luck!
     
  3. BrentD

    BrentD Active Member

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    Thanks. I'll check that out.
     
  4. gjohnson

    gjohnson Well-Known Member

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    Might just be unplugged. Take the back off and youll see.
     
  5. Matt_Krush

    Matt_Krush Well-Known Member

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    Reverb is OP-Amp driven....not tube.
     
  6. RobS

    RobS Well-Known Member

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    the wires soldered to the springs in the tank get a fair hammering when the amp is moved about as the spring is very free moving
    Check those little wires as they have a tendency to break off at the solder joint. you will have to remove the reverb tank to do this and whilst there flip it around so the plugs are easily accessed !
    also, check the V2 12ax7 and the leads as mentioned by previous two posts
     
  7. ricksconnected

    ricksconnected Well-Known Member

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  8. Söulcaster

    Söulcaster Well-Known Member VIP Member

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    Grab a foot switch and try it out. I no longer have a DR, but I used an aftermarket foot switch for channel switching and reverb. Essential if you're using the B channel for solos.

    Peace
     
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  9. wakjob

    wakjob Well-Known Member

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    Yeah, but the signal still has to travel through v2b to get on out of the circuit.... along with the rest of the preamp signal.

    So as long as there is a guitar sound, it's all working.

    Usually disconnected cables or bad tank.
     
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  10. BrentD

    BrentD Active Member

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    It's working now. I think it was just oxidation on the jacks on the tank. Thanks for the input - I know the usual culprits in Fenders but I didn't want to chase those gremlins if the footswitch was the simple answer!
     
  11. John BNY

    John BNY Well-Known Member Silver Supporting Member

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    My JCM 900 had issues with reverb also. It would start to work after the amp warmed up a bit. I replaced the tank and it works great now.
     
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