20/20 EL 84 Wath the heck !!??

Discussion in 'The Workbench' started by marcxxl, Dec 12, 2019.

  1. marcxxl

    marcxxl New Member

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    hi guys,

    My name is Marc and I'm .... French. I know , nobody's perfect :)
    I'"m playing on my Marshall 20/20 EL 84 this 2 past years with no issues( with the JMP1 and the JFx1). In fact, since i bought it. Those days the sound begun to turn very bad an unprecise. I decided to open up the "Thing" for the first time.
    I changed the ecc83 inside that i suspected to be dead. It was the case because it solved the problem. BUT ..... in the place of this ecc83 (V1 position where it is penciled "preamp" on the picture) it supposed to be an ecc82 ... am i right ?
    That's not all ... after that in Vcond1 and Vcond2 there is 2 ecc81 where it is suppused to be ecc83 , am i right again ? For the power tubes there are two EL84 Sovtek and two MESA EL 84 which it seems to be good this time. This Amp was professionally restored in 2010 ,and it seems there was some modifications or repair in it by the previous owner.
    My questions are : what the heck is going on inside this baby ? i mean it worked just fine like this those two past years (at low volume) but this not the genuine configuration. Must i change this or not ? What do you think ? I seriously need some good advices from people who know what they talking about. I'm not a pro in valves amp except for the remplacement of preamp tube with no BIAS set up nedeed.

    Thank you and sorry for my english so rusted :facepalm:

    Amp2.jpg
     
    Last edited: Dec 12, 2019
  2. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    yes, but, the tubes probably don't cause any issue, they just stage the saturation differently...

    I'm not sure about those blue things...

    Here's a little info-vid on different tube types:



    upload_2019-12-12_13-52-9.png
     
  3. South Park

    South Park Well-Known Member

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    How old are the el84s. It should be a matched set .
     
  4. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    it's a stereo amp. 2+2
     
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  5. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    The blue things are probably the 1k 5W HT dropping resistors.
     
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  6. marcxxl

    marcxxl New Member

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    thank you for this video !! Very helpfull :yesway::yesway:
     

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