Pots pots pots ... knowledgeable folk please help.

Discussion in 'The Workbench' started by LayLow87, Jun 22, 2019.

  1. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
    Hi guys,

    Could someone clever possibly spoon feed me a list of the exact model/type of pots I’d need to fully restore the following amps - full set on each. (preferably with what Marshall would use):

    Jcm 800 4010
    Jtm 45 reisssue
    1987 superlead

    Appreciate they might use the same ones in each amps.

    Thanks very much in advance.
     
  2. neikeel

    neikeel Well-Known Member

    Joined:
    Feb 12, 2014
    Messages:
    3,270
    Likes Received:
    1,719
    The 4-holers have the same pot values:
    1M for volumes and bass, 25k middle, 250k treble and 5k presence
    The RI used Alpha chassis mounted, the original 1987 Lead (NOT Superlead - that is a 100w) used CTS type (some AB and some RS labelled).
    Sorry not sure I know what the 4010 is.
     
    LayLow87 likes this.
  3. Dogs of Doom

    Dogs of Doom Moderator Staff Member

    Joined:
    Aug 2, 2012
    Messages:
    18,614
    Likes Received:
    17,887
    Location:
    Los Angeles
  4. ampmadscientist

    ampmadscientist Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    12,683
    Likes Received:
    6,570
    Location:
    Left Coast
    Actually, cleaning the pots with the correct lubricated cleaners will usually solve any problems, and normally it would be unnecessary to replace the pots in most guitar amps.
    It's fairly uncommon to need complete replacement. Just Sayin.

    For Printed Circuit boards, you can get the stock pots which are pretty cheap, or you can find a Bourns Pro Audio equivalent.

    Cheap Stock Pots:
    https://www.tubesandmore.com/products/potentiometers_0?filters=Brand=Marshall

    It's probably worth it to match it for a Bourns part number because the life span of the pot is at least double - 25,000 rotations or more for a good Bourns pot.

    For Hand wired amps you can get PEC, Precision Electronics Company.
    These type pots are going to last 4-5 times longer than the cheap ones.

    [​IMG] PEC is military grade, probably one of the best choices available currently.

    The best resource is to download the manufacturer spec sheets, and check the "rotations rating."
    The better pots will be rated 50,000 rotations.
    The cheap consumer pots will be rated 15,000 or less.
    If you invest in the better pots, it works to your advantage in the long term.
     
  5. Chris-in-LA

    Chris-in-LA Well-Known Member

    Joined:
    Jul 19, 2018
    Messages:
    611
    Likes Received:
    306
    Location:
    Los Angeles
    Good luck finding some of this stuff and you will probably change the way your amp reacts to the knob settings with different pots.

    Jcm800 ‘s
    Pre-amp vol - 1meg log
    Master - 1meg log
    Presence - 22k
    Middle - 22k
    Treble - 220k
    Bass - 1meg log
     
  6. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
    Thank you all for the replies. As to why I’ve decided to do it - each amp has got a complete mixed bag of different pots from 30 odd years of replacement etc. some short solid shaft, some long solid shaft, some short splined etc. Etc.
    All at different turning tapers too. A real untidy mess of different pots.

    As a result I cant seem to get a set of knobs that fit them all tidily and it’s doing my head in (also the fact that as so many are already replaced I’d wager they may not be the values you’ve listed)

    So that’s why I’m planning on giving them all a fresh set. Thanks for the info all.
     
  7. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
    Thanks, 16mm or 24mm?
     
  8. neikeel

    neikeel Well-Known Member

    Joined:
    Feb 12, 2014
    Messages:
    3,270
    Likes Received:
    1,719
    They are 24mm with 6mm shafts
    The 4010 will be pcb mounted and will have Chris's 'modern' values, the RI the same but chassis mounted. The 1987 will have the values that I gave you if it is an original.
    In tests most people find that the vintage amps sound best with high reading pots.
     
    tce63 likes this.
  9. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
    Thank you!the 1987 is an early 1987S reissue from ‘88
     
  10. neikeel

    neikeel Well-Known Member

    Joined:
    Feb 12, 2014
    Messages:
    3,270
    Likes Received:
    1,719
    AMS makes goodpoints re pots, I will always strip, clean and lube the early 60s AB pots as they are very robust. Same with the late 60s Plesseys. The CTS (RS) are around as of course are Alpha and PEC. I would always get solid shaft grub screw type knobs whatever type of pot you choose.
     
    LayLow87 likes this.
  11. Chris-in-LA

    Chris-in-LA Well-Known Member

    Joined:
    Jul 19, 2018
    Messages:
    611
    Likes Received:
    306
    Location:
    Los Angeles
    LayLow87 likes this.
  12. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
  13. myersbw

    myersbw Well-Known Member

    Joined:
    Oct 22, 2015
    Messages:
    856
    Likes Received:
    356
    Location:
    SW Ohio
    Given the "mixed bag" of pot types, I'd do the same thing...buy the good stuff, it's worth it in the long run.
     
    LayLow87 likes this.
  14. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    21,152
    Likes Received:
    8,831
    Location:
    US of A
    Confusions, :scratch:.

    Do you actually have these amplifiers and why do you want to replace all of the potentiometers?
     
  15. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
    Read the thread man! Yeah I own them
     
  16. mickeydg5

    mickeydg5 Well-Known Member VIP Member

    Joined:
    Sep 30, 2011
    Messages:
    21,152
    Likes Received:
    8,831
    Location:
    US of A
    Oooph. I missed the 6th post. :facepalm:
     
    LayLow87 likes this.
  17. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30

    Hi Chris, Do you know what pot id need for the gain knob on a 2205?
     
  18. Chris-in-LA

    Chris-in-LA Well-Known Member

    Joined:
    Jul 19, 2018
    Messages:
    611
    Likes Received:
    306
    Location:
    Los Angeles
    On the schematic I checked they all look to be 1 meg log.

    8187ED41-AAD3-4D26-BAF4-227048C941DD.jpeg
     
  19. LayLow87

    LayLow87 Member

    Joined:
    Jan 7, 2013
    Messages:
    75
    Likes Received:
    30
    24mm?
     
  20. Gunner64

    Gunner64 Well-Known Member

    Joined:
    Nov 16, 2013
    Messages:
    4,606
    Likes Received:
    4,974
    Location:
    Midwest, USA
    The gain pot in the 2205 drive channel is dual gang.
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice