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Topics - El Scorcho

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The Newcomer's Forum / Marshall 5010 Needs Help
« on: March 18, 2018, 09:32:21 AM »
Total noob here, with little electronics experience beyond wiring guitars. I just picked up a 1982 Marshall Master Lead 30 combo for 50 Euros, so it's not like I was expecting much. I had a Lead 20 back in my teens that I remember liking alot, but this thing sounds like a moist fart.
   I opened it to clean it out and saw that D2 is missing entirely and D1 is not a diode, but a 2n2 Cap. Someone has tagged the bottom of the chassis with a permanent marker W.A.M Workshop And Music.  Has someone actually done something clever, or really stupid? Even on low gain setting there is an unpleasant 'fizzy'coating. I gave W.A.M the benefit of the doubt and swapped out the Red McKenzie out for a Celestion G12L, which made the moist fart sound like a bit more carefully executed fart, so now I'm leaning toward stupid.
 I've researched the other 5010 posts here, and bought a 500k reverse log to replace the V1, but now I'm wondering if it's worth the bother. Looking at the Schematic, D1 and D2 seem to have something to do with Voltage supply, and I wonder if this mod hasn't burned out something else. The amp powers up and seems to work  - it just sounds more like a 1-knob, particle board starter amp from an old Sears catalogue than a Marshall.
    I'm going to go ahead and replace D1 and D2 with fresh 1N914's, and hope that helps. Is there anything else I should worry about? Like maybe R23/24 and C19/20, which seem to be in the same loop? Would this mod have ragged out the op-amp? What would the point of such a 'mod' be? A poor man's variac?
    Sorry in advance if I'm wasting anyone's time, but certainly would welcome some insight.

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