Some Mods for Marshall Class 5

Discussion in 'The Squawk Box' started by Lyle Caldwell, Jan 18, 2011.

  1. Splattle101

    Splattle101 V.I.P. Member

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    When was the last time Lyle swung past?
     
  2. Ejfalla

    Ejfalla Junior Member

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    Hi everyone
    I bought the Class 5 with atenuator.
    Have read every post. I am looking forward to doing ( my tech will be doing it ) Lyle's mod posted in the 1st page.

    Please somebody has the final C5 sheme ( with the mods high lighted). ??


    Thanks in advance for your replays !!
     
  3. gouna

    gouna Member

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    Hello,
    Is it normal that the "brigth switch mod" is heard only with the guitar volume pot is at maximum?
    If I lower the volume of my guitar, the effect "brigth" is no longer present (nothing to do with the wiring, I'm already in 50's gibson wired).

    Your opinions?

    Thank you. (sorry for my bad english....)
     
  4. Stormydave

    Stormydave Junior Member

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    Hi all, I'm new here and appreciate this is an old thread, but I've just acquired a Class 5 Red Roulette Head, made in 2014, issue 4 PCB and I've done the Lyle Caldwell mods to it. I have a problem that I cannot track down. After completing the mods and powering up, everything works normally i.e. amp switches on, tubes power up, there are no odd noises, but the volume level is only what it would be on 0.1w headphone mode, even with the volume pot fully up and running in the 'normal' speaker mode. The thing is driving the tubes as I can hear it distorting as the volume goes up. It sounds 'right', all pots are working and having an effect on the sound, the only issue is there's no volume to speak of. I'm hoping someone can point me in the right direction to identify what's wrong. I've done the mods exactly as described by Lyle, except I haven't fitted switches and the 68p Fizz Cap is not currently installed. Some other notes about how I've done this:

    R9 is removed
    I don't have links L19 / L18, so the 120p bright cap is fitted across lugs 1 & 2 of the volume pot
    C10 is removed and has been re-used across R12
    C13 has been removed and replaced with a link
    C20 has been replaced with what was in C13
    C2 has been replaced with what was C20
    C8 has been replaced with a 1uf electrolytic, correct polarity has been observed
    All resistors have been replaced with the values advised by Lyle

    I have checked and re-checked all connections and soldering, cannot find any bad ones. I have checked and re-checked all components, cannot find anything bad. I have checked and re-checked that I have the right bits in the right places and can't find a problem. I've also replaced all tubes, this has no effect either.

    Do any of the caps I've moved have polarity requirements?
    Can anyone suggest what might be wrong?

    Many thanks in advance of any help that can be given.
     
  5. Stormydave

    Stormydave Junior Member

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    OK, so C22 is showing nil resistance on my multimeter. Not sure if this is the problem, but I don't think it should show 0 ohms. I haven't touched this cap by the way. I've ordered 10 Wima 22n 400v caps, so I will replace everything that needs this value with these, include C22. We'll see what happens then.
     
  6. Stormydave

    Stormydave Junior Member

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    I've found the cause of the problem. The electronic components supplier had supplied the wrong resistors. What should have been 470k ohms were actually 0.47 ohms, so no wonder it wasn't working! All my work was correct, all fixed and working now.

    My god, what a difference this makes to the Amp! It is a different beast altogether, fantastic now. Also fitted the VVR Master Volume (works great) and a 190k resistor to R51, to increase the attenuated volume level to something respectable but still usable at home.

    Thanks to Lyle Caldwell for these great mods from a few years back, still as relevant today.
     
  7. greezy strings

    greezy strings Junior Member

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    Hello, 1st off thank you Lyle Caldwell for the mod info. Had it done on my class five a couple years ago and loved it.. Today after a month or two of not playing the amp.. I turned it on and noticed the tone to be very bright.. especially when the I strum hard and or volume pot on guitar is all the way up. I have to turn the treble tone pot on the amp all the way down as well as the treble on my guitars. I have tried 5 different guitars, 3 different cabs and various cables including speaker cables. I noticed that the tube in V2 position was not glowing as strong as v1 preamp tube? I took the pcb board off and went through it best I could ( far from a semi- pro but can do basic repairs.) it seemed like the r21 (which looks like has a added resistor going across it) was a little loose so I re-soldered that. otherwise I can not see anything else. I swapped out the pre amp tubes with some jj 12ax7's I have in my other amps. Same , lot of treble. I do not have a extra power tube on hand so could not switch that out.. not sure if a power tube can cause this issue. Any help would be really appreciated. I know it is a old thread so hope some of you out there are listening in. Thank you very much guys and gals.!!!
     
  8. JOESHMOE

    JOESHMOE Senior Member

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    I finally got tired of trying to make my class 5
    sound right so I traded it and $58 for a Boss
    Katana 50 and it sounds 10 times better and is
    100 times more versatile.

    Jimmy
     
  9. bulletproof

    bulletproof aka tarddoggy Premium Member V.I.P. Member

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    I still love mine....damn thing is a beast!:headbanger:
     
  10. bblooz

    bblooz Senior Member

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    Quitter!
     
  11. greezy strings

    greezy strings Junior Member

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    I really like mine pre mod and post mod.. just trying to figure out why the highs are all of a sudden bright and a bit piercing even with the treble turned all the down??? Im kinda bummed.
     

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