I can open it up and take a picture but will not do me any good... photobucket has prevented me from sharing pictures. Need to find an alternate source for hosting photos. Any recommendations?
The capacitor sits very close to the V4 socket, close enough that the reference designator is covered by the plastic base. The cap is blobbed over with silicone glue, and is in-line with a molded axial leaded tantalum capacitor (used for the bright switch controlled by a JFET). Note: if this mod had failed to impress me or if it was a mistake, I would not have posted it. I know someone else is looking into doing something similar but may or may not do it. There is a similar cap on V6 and that should be left alone. Only one part. If you love the amp as is, do nothing and be happy. If your amp does not have the component from the start and you think you are removing the suspect part, you may be removing the wrong thing. I was not very happy with the Mark V so it made no difference to me if it became better or worse, went up in smoke or just stopped working. (surely I jest).
I have noticed the amp is a bit louder without the 120pF capacitor, not by much but definitely louder, bottom end is tight and the response of the pick attack is on par with the JP-2C. Before the capacitor removal, the bottom was a bit muddy, lower midrange was minimal and the upper mids and top end dominated the signal. (OK in tone and character, just not very impressive and becomes tiring after a few minutes of playing) The 12AT7 before the component removal did improve signal characteristics but did not correct for the mud in the bottom as much as I would have preferred. After the component removal, the amp was more lively, responsive to pick attack and bottom end was tight. With the 12AX7 it was much brighter but no ice. With the 12AT7 installed it was heaven. It is like a new amp, different but similar. Lower mid range is thick as is the upper midrange. The amp is still bright with the 12AX7 or the 12AT7 but not brittle at all. The 12AT7 is better in terms of gain control and saturation levels. No compression as I found note definition has been improved. I can take a picture of where the capacitor was..... Body of the cap is round ceramic, school bus yellow in color, 121 (120pF) and 1kV (1000V) is printed on it (when I found the part, the printing was facing the other capacitor that it was glued too. I had to use process of elimination to find it by checking continuity to pin 8 on V4 and component leads, as well as pin 7 to component leads. It was the only part that shares electrical connections to both terminals. I believe the Reference Designator is C39. It is a tight squeeze to get in but manageable. Small tools are needed to remove it. I originally was going to just cut one leg but opted to remove it completely as it would be easier to install a new one rather than trying to solder the cut leg together if the side effect was not desired. There is no guarantee your amp even has the part, I was uncertain if it was there as it is common to see components on the schematics and not on the assembled PCB if it was omitted on purpose based on revisions. Also the schematics were based on the 2009 version but so far has held up to reference designators being actual. However it does not include the switch logic and some other features that would be helpful in repair if needed.
sorry to bring back bad memories, somehow I understood all that stuff and I do remember the challenge was fun to some extent, do I use it now? No. Should I? probably.... :roll:
