Tweet
I picked this up a few months ago. I did a little research while I waited for it to arrive, placed a parts order and dove in. It's such a pleasure to work on these. Just remove the top and everything is right there. 
Service related
A) Filter cap replacement, two 2 x 50uf /500V cans replaced the old 2 x 40uf dynamite sticks
Plexi mods
B) Replaced 470k volume controls with 1meg volume controls. Used pull switch pot on the bright channel which lowers the cathode resistor value and adds a bypass cap for a gain bump.
C) Replaced 100k mixing resistors with 220k
D) Tone stack shift – replaced .01 & .1 caps with .022 caps
E) Tone stack shift – replace slope resistor with 33K & replace 320pf cap with 500pf silver mica cap
F) Re-purposed the old ground switch to switch the feedback resistor between the stock 100K and 33K which adds some sag. I actually like the stock position best because it has more punch in that position.
Tubes
V1 - I63 Blackburn Mullard
V2 - Short Plate Sylvania
V3 - Long Plate Sylvania
Power - Tested and kept a pair of Mesa labeled Shuguan EL34/6CA7's
I snapped this picture before I added the cathode bypass cap which is installed parallel to the resistor coming off the top right corner of the board.
It pretty much mops the floor with my old Plexi reissue and is my favorite amp.
Here it is with a stock MIM Telecaster and a SD-1 set with the standard 4-holer setting, vol at noon, tone at noon and drive at 1 - 2. The amp is jumpered with channel one at 5 and channel two at 8 with the pull pot out for MOAR.
Service related
A) Filter cap replacement, two 2 x 50uf /500V cans replaced the old 2 x 40uf dynamite sticks
Plexi mods
B) Replaced 470k volume controls with 1meg volume controls. Used pull switch pot on the bright channel which lowers the cathode resistor value and adds a bypass cap for a gain bump.
C) Replaced 100k mixing resistors with 220k
D) Tone stack shift – replaced .01 & .1 caps with .022 caps
E) Tone stack shift – replace slope resistor with 33K & replace 320pf cap with 500pf silver mica cap
F) Re-purposed the old ground switch to switch the feedback resistor between the stock 100K and 33K which adds some sag. I actually like the stock position best because it has more punch in that position.
Tubes
V1 - I63 Blackburn Mullard
V2 - Short Plate Sylvania
V3 - Long Plate Sylvania
Power - Tested and kept a pair of Mesa labeled Shuguan EL34/6CA7's
I snapped this picture before I added the cathode bypass cap which is installed parallel to the resistor coming off the top right corner of the board.
It pretty much mops the floor with my old Plexi reissue and is my favorite amp.
Here it is with a stock MIM Telecaster and a SD-1 set with the standard 4-holer setting, vol at noon, tone at noon and drive at 1 - 2. The amp is jumpered with channel one at 5 and channel two at 8 with the pull pot out for MOAR.
Comment