V2a":j6s3uybu said:It's hard to tell what is connected to that pot from the photos.
- It doesn't look like anything is connected to one gang of the pot (the one farthest from the faceplate); is that correct?
- Does the blue/wht striped wire connect to a lug of the front-most gang?
- What else is connected to that pot?
- What is that WIMA .68uF cap connected to?
- Did the stock amp have a presence control?
Rick Lee":1zzwkt7p said:Can't you just get a layout of the stock version and copy that? What year is that one supposed to be? '68?
SpiderWars":3s8zjgx2 said:Is that 430k total NFB resistance? Looks like a 330k was added in series with the board-mounted 100k (the resistor-to-ground part of the NFB divider is the standard Marshall 4k7, dangling off the opposite side of board as the 330k). If so, that's not very much NFB. Does the Presence even work very well?
My guess is that the person did not have the right value pot (usually 25k-L) and just used what they had.
EDIT: and FWIW and IMO, just based on the photos you posted, there is not a lot going on in that amp. Pretty much any tech (even a hack like me) should be able to hook you up.
JerryP":qvk6izgk said:Hard to see in those pics, but the presence pot appears to be wired up normally. Only one half that pot is used. Maybe a different value pot? There's some other stuff going on there, but the presence pot looks normal.
gtrwun":3swg1vdi said:Rick Lee":3swg1vdi said:Can't you just get a layout of the stock version and copy that? What year is that one supposed to be? '68?
http://www.guitaramplifierblueprinting.com/jw1.html
If you know where I can find a schem or layout, PLEASE , point me in the right direction. I've tried to contact Jim and he has never replied.