For now, just substitute the pots and try it.
Transistors are normally very reliable unless they are the old, Germanium types. Early silicon types could go noisy and / or intermittent. They may just simply open. Your more likely issues will come from electrolytic capacitors, some early polystyrene types (like to short), and sometimes resistors. Carbon composition resistors can drift way high in value while they look perfectly fine.
You really do need an oscilloscope. You can't "see" electric current or voltage. A decent DVM allows you to see steady state DC, and expensive DVM can show accurate, steady state AC voltages, but you really do need an oscilloscope to get a picture of what is going on. So please, get even a 10 MHz, dual trace analogue oscilloscope. They aren't much less than a decent 100 MHz dual trace oscilloscope from Philips or similar quality brand. You do not want a digital oscilloscope for audio service.
-Chris
Transistors are normally very reliable unless they are the old, Germanium types. Early silicon types could go noisy and / or intermittent. They may just simply open. Your more likely issues will come from electrolytic capacitors, some early polystyrene types (like to short), and sometimes resistors. Carbon composition resistors can drift way high in value while they look perfectly fine.
You really do need an oscilloscope. You can't "see" electric current or voltage. A decent DVM allows you to see steady state DC, and expensive DVM can show accurate, steady state AC voltages, but you really do need an oscilloscope to get a picture of what is going on. So please, get even a 10 MHz, dual trace analogue oscilloscope. They aren't much less than a decent 100 MHz dual trace oscilloscope from Philips or similar quality brand. You do not want a digital oscilloscope for audio service.
-Chris