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SL-X replacement PCB

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

  1. Matthews Guitars

    Matthews Guitars Well-Known Member

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    PC board construction is fine if you do it right. A few rules to follow for serviceabilty and reliability:

    Don't use smaller components than you NEED to. Bigger components are easier to handle, easier to replace, and can dissipate more power, contributing to reliability.
    Size thru-hole lead holes so that the leads pass thru the board with room to spare. This allows them to be easily installed and, maybe just as importantly, easy to desolder
    and replace without damaging the board.

    Always use plated-thru holes and specify a copper trace weight that's MORE than the bare minimum. 2 ounce copper traces, plated thru, are good for just about everything. Yeah, Marshall didn't do that but Marshall always has gone for "good enough" and "don't spend a penny you don't have to spend.". Their ST1 boards are known for dropping traces after being touched by a soldering iron a few times. Just because Marshall was cheap doesn't make it a good way to make a board.

    Don't mount parts on a PC board that are going to be subjected to thermal or mechanical stress. Keep the board cool and it'll outlast the steel chassis it's mounted in.

    Try to put all wiring and connectors along ONE edge of the board so the board can be rotated upwards for access to the back side, if repair is needed. If this is impractical, try to include a service loop in the wiring if it doesn't create problems.

    Always consider the possibilty that you may have to repair your own board. So design it to be easy for you or anybody else to access and repair. Always think serviceability.

    Solder mask is a good thing. So is a printed layer showing component values and information for the service technician in the future.
     
    Last edited: Apr 28, 2021
  2. 961le

    961le Active Member

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    had to use a massive copper pour to hit all ground refs. this board has no pth but in that way its like the original. im still learning this stuff. if i have to do it again so be it. itd be a little longer this time, im tapped at the moment
     
  3. 961le

    961le Active Member

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    Continuity check good. Moving on to components
     
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  4. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    I still can't believe that they purposely made your 1st batch unusable... :facepalm:
     
  5. Yamariv

    Yamariv Well-Known Member

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  6. 961le

    961le Active Member

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    70EC7AA5-A764-4EBA-84E9-CFC455732F74.jpeg
    How can I not have even 1 27k resistor in my stash??
     
  7. 961le

    961le Active Member

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    I know it. But, I’m glad it worked out the way it did. I still would have remade them. Jumpers don’t belong on a new board. Especially one I sent out for fab. Nobody to blame but me. I did learn a lot from that mistake. And they knocked some money off even though I changed the board files. They would’ve resent the originals at no charge but I refused willing to pay for my own error.
     
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  8. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    that's cool, if you feel they've made it right, who am I to quibble?
     
  9. ibmorjamn

    ibmorjamn Well-Known Member

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    I am very interested still.
     
  10. 961le

    961le Active Member

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    Yes it’s go time. I’ve run out of shade. I’m waiting on some flux to come in. Should be tomorrow and I’ll get the iron hot. I’m thinking sat afternoon or Sunday before I can swap boards. There is a lot to do until then though. I decided to parallel two 56k resistors. I’m not ordering a few resistors only.
    There are still holes to drill for the bracket screws that go to the chassis. I have to measure for those and am not pulling the chassis tonight
     
  11. 961le

    961le Active Member

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    4637D9A3-5D2C-4131-A9E4-9BCD7654413D.jpeg Soldered so far
     
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  12. Brett336

    Brett336 Member

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    I have to tell ya, this is really some love for an SL-X
     
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  13. 961le

    961le Active Member

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    If it doesn’t make sound there will be some hate.
     
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  14. ibmorjamn

    ibmorjamn Well-Known Member

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    You have done a great job so far .
     
  15. 961le

    961le Active Member

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    Thank you sir.
     
  16. 961le

    961le Active Member

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    81A710E3-9FFB-468F-94CF-7F1F3CE35CD3.jpeg
     
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  17. Axeplyr

    Axeplyr Member

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    The suspense is killing me. :ohno:
     
  18. 961le

    961le Active Member

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    871AC5A5-12C9-4D08-BE77-C49BF475EA27.jpeg

    missed a capacitor on my parts sheet. Looks like I have to order one. I’m debating robbing it from the original. I haven’t decided yet how to proceed . 1 10pf cap brought me to a screeching halt. Had to work and bury a friends mom today ,we go way back. It’s been a bummer of a day and these events are getting way too frequent
     
    Last edited: May 1, 2021
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  19. Dogs of Doom

    Dogs of Doom Moderator Staff Member

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    the like is for the progress, not the bummer of a day...

    sorry to hear...
     
  20. 961le

    961le Active Member

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    Thx, the cap from the original amp is one of the axial green ones. Can’t make it work. Looks like mouser order going out
     
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