Marshall 1987x C5 Cap Modding Results

Discussion in 'The Workbench' started by paulorr8179, Mar 2, 2021.

  1. paulorr8179

    paulorr8179 Active Member

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    Comrades -

    Those who have a 1987x know the high treble loudness goes from low volume to outright LOUD at about 3. I read about sniping cap C5 to tame the map.

    I took out cap C5 4700 pf off the board. I thought the difference was good but I missed not having the high gain roar when I wanted it. I read about moving the cap from C5 spot on the board to the middle and outer lug of the loudness pot. I put a 360 pf cap across the high loudness pot and that worked good.

    But I wanted my cake and eat it too. I wanted the stock 1987x growl, and the Marshall bassman sound when I wanted it. So I got a SPDT 3-position (on-off-on) switch, wired in both the original 4700 pf cap and the 360 pf cap to the switch. I removed the top position normal input jack, and in its place put the SPDT switch.

    In the up position, its full on 1987x via the 4700 pf cap. In the middle position (off) it is bassman (all caps off). In the down position the 360 pf cap is in play, giving some gain but not over the top. (Think Fargen's 60's, 70's and 80's decade switch.)

    But wait there's more. I thought the normal channel sounded muddy. So I put a 100 pf on there inner and outer lug of the normal loudness pot so to allow some treble through, rendering the normal channel more Fender Deluxe sounding, not muddy like the stock sound.

    I provided some pics in this thread. And a diagram of how I wired up the two caps to the switch.

    The only mod to the chassis was I had to open up the diameter of the normal jack position to fit the new SPDT switch.

    Anyone attempting this mod, it is easy. Use the middle lug and the right lug of the volume pots when looking from the rear of the amp.

    Enjoy!

    Paul
     

    Attached Files:

    Last edited: Mar 2, 2021
    Dogs of Doom likes this.
  2. South Park

    South Park Well-Known Member

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    Good gob on that signal cable . That circuit is not easy
     
  3. paulorr8179

    paulorr8179 Active Member

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    I’m really happy with the result. I was buying and selling boutique amps looking for a Marshall sound and one day I said what are you doing man just buy a plexi. Problem is I just couldn’t leave it alone. LOL
     
  4. neikeel

    neikeel Well-Known Member

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