This has nothing to do with stainless steel refrets or guitar repair. But it will be useful to some. I have a Crate V32 which are little diamonds. Crate built some fine tube amps in these and the V16 before they went bust. They are all tube, can be picked up for a song and have everything you need in a tube amp. If you want you can easily modify them. I have made some changes myself that I will post. But mine like most didn’t come with a foot switch. I couldn’t find one and old Crate foot switches were kind of junky. So I bought a Hosa FSC-385 a solid little bugger that was so cheap I couldn’t believe it but it had no lights. So sometimes I couldn’t tell if I had channel 2 selected or the boost or both or none depending on how I was running my setup. So it was time to add some LED’s and it cost me nothing because I had two LED’s handy that I’ve had for 20 years, yep 20 years! Here is how to do it. It is very simple.
Before proceeding here is the disclaimer. This works perfect with my V32. The foot switch schematic is shown. As far as I know all V32’s are the same. Do not try this with a V16 unless it has the same circuit. If you don’t know don’t do it.
Reference the schematic. What you are doing electrically is putting LED’s in parallel with D11 and D15. Those are the two zener diodes that control the transistors for the Channel select circuit and the Boost circuit. When either tip is grounded by the foot switch transistor Q2 or Q3 of each respective circuit will turn on which turns off boost or selects the clean channel. This is normal state. When the foot switch tip is open Q2 or Q3 is turned off and Boost or Dirty Channel is activated and the respective LED’s conduct and light up.
The LED’s draw current via R63 or R68 in their respective circuit. When tip is grounded the LED’s are off. Using ohms law the maximum current draw is about 11ma well within range of an LED so no worries. But the LED’s are in parallel with the D11 and D15 zeners which limits the voltage across them to 3.3 volts. I measured the LED current draw and it was about 7ma. That implies the internal resistance of the LED is ~470 Ω. The bottom line is you don’t have to add resistors or anything other than a standard LED to the footswitch.
Follow the pictures and enjoy your new LED’s!