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SL-X replacement PCB

Discussion in 'Marshall Amps' started by 961le, Feb 20, 2021.

  1. 961le

    961le Active Member

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    the board outline is complete , got it down to 14x3.5 inches. making changes to some pads and ground turrets at this point. after i triple check all items i can begin tracing. It is taking a while but learning what to do is pretty entertaining and its not like i dont have an operational amp to use. there is no need to rush. at this point i would say im a few weeks out as i only have an hour or so each night of free time.


    View attachment 86807
     
    Last edited: Mar 17, 2021
  2. 961le

    961le Active Member

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    12 pounder... what a pig. ill bet it sounds great. i had a standard in cherry burst. 89 model. guitar teacher at the time told me it was the heaviest lester he had ever played. it sounded awesome. I got wed needed some cash and made the first biggest mistake of my life and sold it. now i have neither one :) saw the dude in the grocery store years later and wanted to buy it back. it was not for sale.
     
  3. 961le

    961le Active Member

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    Small progress had to work today
    7932F50B-0DDC-492A-BF56-BA675FBBFD7C.png
     
  4. 961le

    961le Active Member

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    .
     
    Last edited: Mar 21, 2021
  5. 961le

    961le Active Member

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  6. 961le

    961le Active Member

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    The nets did not work. I’m manually connecting traces. Notice the three rivet holes for the bracket that I will fab after boards come in. I’m close but another week or so. EF838CA3-D250-4E09-9EC0-9EEDB4129706.jpeg
     
  7. marshallmellowed

    marshallmellowed Well-Known Member

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    I would recommend laying out the BR3 section for a larger rectifier (more current handling), not the smaller version that overheats. I'm also guessing the original traces may have not been thick enough, so maybe increase the thickness, if you haven't already thought of that. Just some suggestions.
     
  8. Matthews Guitars

    Matthews Guitars Well-Known Member

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    Suggestion: Take the pots off the board and hand wire them in. It makes the board more serviceable, you can use full size CTS pots, and you free up board space for components that the pot footprints are using now.

    The biggest gripe of most Marshall techs seems to be about Marshall moving the pots to a PC board. That makes servicing more difficult.

    I know that I strongly disagree with putting hand-operated switches and pots on a PC board. I also even more strongly disagree with mounting tube sockets to a PC board. Things that get hot or are subjected to mechanical stresses should not be on the main PC board of the unit. They compromise reliability and serviceabilty.

    Marshall's justification for putting the pots on the board is simply cost savings. It eliminates the labor time required for wiring up the pots by hand.
     
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  9. 961le

    961le Active Member

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    The bridge rectifier comes in larger amperage in same footprint. I’ve been successful for years now on a 2amp version elevated off of the board.
    This project has been taken on to see if I could do it by myself. It is much harder to hit holes already punched. That was the challenge. I want it like new. If I mess up I can always lower the board with a different bracket and put std pots in. Things can still go awry. They may punt my files back who knows. I’ve still learned something I didn’t know before which makes for a good day. The traces are actually a hair larger than stock( a gnats hair) real estate is valuable.
     
    Last edited: Apr 7, 2021
  10. marshallmellowed

    marshallmellowed Well-Known Member

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    Nothing wrong with board mounted pots, as long as the shafts are secured to the front panel, which I believe the SL-X pots are. As for the traces, I was referring to thicker, not wider. Good luck, hopefully someone will make it for you. A problem you may run into, is a higher cost due to the small quantity.
     
  11. 961le

    961le Active Member

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    On the slx the bracket supports the pots. Three screws secure the bracket to the chassis. Pull the knobs and remove the screws and it slides right out. Have to buy 5. Around 65 to 75.00 us. Way cheaper than buying another amp which I was going to do.
     
  12. 961le

    961le Active Member

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    Anything can happen but I don’t see why I shouldn’t be able to order boards this weekend. If all works out, and the manufacturer accepts my files. Traces finished just grounds left.
     
    Last edited: Mar 27, 2021
  13. 961le

    961le Active Member

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    E3631877-D175-4A81-95C3-36C6B7AD7C24.jpeg In process of ordering now, files under review.
     
    Last edited: Mar 28, 2021
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  14. 961le

    961le Active Member

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    Ordered. 5-7 days should have in hand.
     
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  15. mad5066

    mad5066 Well-Known Member

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    Props to you, I hope it serves you well! Cool project
     
  16. 961le

    961le Active Member

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    Boards are manufactured just not shipped yet.had a few days of communication issues with manufacturer. Pushed me right into a natl holiday. It’ll be wed or Thursday before it ships to me. Patience young padawan
     
  17. FleshOnGear

    FleshOnGear Well-Known Member

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    I’m excited to find out how this comes together. Are you taking the parts off of the original board? Or did you order all new components?
     
  18. EADGBE

    EADGBE Well-Known Member

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    You may just want to leave it as is. A new PCB may sound totally different.
     
  19. 961le

    961le Active Member

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    I’m building it completely new pots and all. I hope I can land a few opamps before they are no more. I’m going to buy a few of them. If it’s a turd I’ll put the original back in:) but I still have to hope my measurements are accurate on the pots and jacks spacing. I’d have thought it would be metric but pots are 1.25 on ctr. I’m not going to just solder them in but fit them in the holes and then solder the board to the pots. I put in a hair of wiggle room. Like any new amp I’ve had when the caps are new it doesn’t sound worth a crap for about 15-20hours. My biggest question is I don’t know whether to put micas in or the ceramic discs like the factory did. I’m using Wimas on the coupling caps. Mine came with orange drops originally.
     
  20. EADGBE

    EADGBE Well-Known Member

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    Good luck! And post some clips when you can. [​IMG]
     

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