Results 1 to 6 of 6

Thread: JMP-1 encoder mod

  1. #1
    Senior Member
    Join Date
    Feb 2007
    Location
    Iowa
    Posts
    1,392
    Thumbs Up/Down
    Received: 11/0
    Given: 2/1
    Rep Power
    14

    JMP-1 encoder mod

    Ive read in other forums about fixing the data wheel issue in the JMP-1 Marshall preamp. I just got one and the patches jump around when turning the control. I guess this is common in these units . They are adding a de-bouncing chip. No one mentions "how"

    here : https://www.mouser.com/ProductDetail/863-MC14490DWG

    https://www.mouser.com/ProductDetail...CW1J-C36-CC24L


    so the encoder is 3 pins and the chip is 16 pins.

    Has anyone done this mod? Is there a scem , or can someone tell me how to do this ??

    0 Not allowed! Not allowed!

  2. #2
    Senior Member Pedro Vecino's Avatar
    Join Date
    Jul 2006
    Location
    Spain
    Posts
    619
    Thumbs Up/Down
    Received: 149/0
    Given: 77/0
    Rep Power
    13
    When the encoder ages it tends to be unstable, making the adjustment difficult.
    When it is new, its precision is total.
    Sometimes I have cleaned them and they work better, but if the degradation due to use is excessive, it is enough to order a new one.

    0 Not allowed! Not allowed!

  3. #3
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    11,412
    Thumbs Up/Down
    Received: 1,357/21
    Given: 3,361/8
    Rep Power
    22
    "The circuit I used was just the standard circuit in the MC 14490 data sheet, and I attached the PCB to the back of the encoder with foam tape."

    http://www.marshallforum.com/threads.../#post-1167049

    0 Not allowed! Not allowed!
    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

  4. #4
    Senior Member
    Join Date
    Feb 2007
    Location
    Iowa
    Posts
    1,392
    Thumbs Up/Down
    Received: 11/0
    Given: 2/1
    Rep Power
    14
    i found some help--thanks though

    0 Not allowed! Not allowed!

  5. #5
    Lifetime Member Enzo's Avatar
    Join Date
    May 2006
    Location
    Lansing, Michigan, USA
    Posts
    31,632
    Thumbs Up/Down
    Received: 1,525/7
    Given: 0/0
    Rep Power
    54
    Debounce? It didn't need debouncing when the parts were new. Seems like a lot of extra effort to get around replacing a worn control.

    0 Not allowed! Not allowed!
    Education is what you're left with after you have forgotten what you have learned.

  6. #6
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    11,412
    Thumbs Up/Down
    Received: 1,357/21
    Given: 3,361/8
    Rep Power
    22
    Apparently the datasheet for the encoder shows a recommended debounce circuit. Not sure if that means it is recommended to use one, or if it means if you are using one, here is the recommended version.

    0 Not allowed! Not allowed!
    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Fender cyber twin replacement encoder problem
    By Klemay83 in forum Maintenance, Troubleshooting & Repair
    Replies: 2
    Last Post: 03-23-2018, 10:14 PM
  2. Digitech rotary encoder
    By Mick Bailey in forum Guitar Effects
    Replies: 6
    Last Post: 06-04-2015, 05:00 PM
  3. Marshall encoder
    By Valvehead in forum Maintenance, Troubleshooting & Repair
    Replies: 6
    Last Post: 11-29-2014, 02:19 AM
  4. 15 position rotary encoder?
    By ricach in forum Guitar Effects
    Replies: 10
    Last Post: 03-30-2011, 01:48 AM
  5. Digitech Whammy Rotary Encoder
    By EstynEstyn in forum Guitar Effects
    Replies: 2
    Last Post: 03-18-2011, 07:30 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •