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Recently, out of necessity due to an emergency situation (power valve leaking live current and making the amp unusable and in-fact-deadly ? ), I replaced two of my amp's four JJ E34L's (not a type-o) with two new regular JJ EL34's. (courtesy Of Shaun on the forum, resident Marshall-Man) This was over a month ago, and as of the last week, when I turn the amp on, and then the standby to on, The amp gives a mighty screech like a Ring-Wraith and then proceeds to operate normally. Is this because of the mismatched valves? (although effectively both EL34's they're still two independantly matched pairs, and not a matched quartet, as was what I originally put in the amp before the replacement was necessary).

Is there any quick way to remedy this, or do I have to buy a whole quartet again (I re-valved the amp 9 months ago)??
    I think you have a dodgy power tube. Try test the set in another similar amp (if possible) to see if the effects are the same.
      15 days later
      For interest sake, did you ever come right with this?
        Yeah, one of the E34L's went microphonic last week, so I just bought a new quartet of matched EH EL34's from Mr Valve.

        My conclusion is that the E34L's were finished anyway (3 or 4 hours a day of use ? )

        Having a matched quartet again is a huge improvement, and the EH are really tight and punchy in the bottom, but smooth and rich sounding so far.
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