Long time lurker, but finally having an issue that I needed advice on. Working with a Spider Valve MKII 212 combo, I noticed after I got the amp home that the Presence knob wasnt changing anything. Unless it was maxxed out and then tapped a couple of times, there would be no tone change, so my first thought was there must be a short in the cable that carries the signal from the Presence knob to the "motherboard" (forgive me, Im a computer nerd so when i cracked the amp open, thats how i related the components). With me being able to access the cable without touching anything else, i noticed that when the "Presence" cut out giving me a super dark tone, if i lightly touched the cable anywhere, the "Presence" would turn back on.
So while trying to heed everyones warnings about how bad i could get hurt in there, ive been trying to troubleshoot whether or not there is anything i can do OTHER than getting the Presence pot replaced. I tried cutting the cable and splicing it (it looked like the zip tie was super tight and couldve broken the copper inside causing an intermittent short), but no difference occurred. I tried seeing if there was another cable that I could use but unfortunately the only other cable with the correct connectors connects the motherboard to the "feedback" board. For a few minutes I had considered removing the master volume pot and resoldering it in place of the Presence pot(since i can control the master volume with the FBV), but when I disconnected the Master Volume pot on the front panel(via its link cable, i didnt actualy remove the pot yet), there was no way to slightly adjust volume even with the channel volumes set low and the volume pedal setting set to max 3%. So now I know that I have to keep the master volume pot.
which leads me down to what i think my only option is, getting the Presence pot replaced. While it seems easy enough, as ive tons of experience soldering electronics from a young age, I was hoping there was another option available? Looking at the location of the pot, and how its on a small mini-circuit board, i could easily have enough room to suck the solder off the old pot, install the new pot and resolder, but I cannot find anywhere in the schematics as to what pot to purchase? I can live without my Presence control for now, as bypassing it doesnt hurt the tone dramatically, but I cannot get it as bright as i would prefer. If my understanding is correct, the pot is not simply a means to "cut" frequencies.... its actually a cut/boost pot. So disconnecting it affected my tone the same as if the pot was still in action but set to the 12 o'clock position, without the ability to increase or decrease brightness. Has anyone tried replacing their presence pot before?