As for the condition of the pinch roller rubber, there are two main degradation modes: either the rubber develops cracks (easy to check visually so I won't elaborate on this) or it goes soft.
To detect soft rubber, all you have to do is press the end of a fingernail against the surface. Rubber in good condition does not show any trace, while aging rubber that has gone soft shows a mark that disappears quickly. If this happens, you can try rejuvenating it with naphta (aka lighter fluid) or a more specialized compound (I have a can of AF Platenclene for this). Apply and rub gently until the soft outer rubber is removed and the fresh rubber underneath appears. This method does not always work however, and your best option is usually to have your pinch roller re-rubberised, or to get a new pinch roller depending on the cost.
You can also detect an aging pinch roller by its symptom, which is an elevated wow & flutter. This is easy if you have an W&F meter, but if you don't have one you can use a computer with a sound card and dedicated software like WFGUI (free) or the Nakamichi T100 emulator. I won't insist on these as there is an easier and free solution, which does not measure the W&F but allows you to check rapidly whether your recorder has a W&F high enough to be a problem. Record a couple of minutes of piano, and play it back. If you can feel the flutter, then you know that you have a problem and a bad pinch roller is the usual suspect. Why piano? Well, it is by far the most sensitive instrument to flutter: voice or a continuous tone don't show it nearly as easily. The threshold of audibility varies from person to person, but personally I can consistently detect 0.1% weighted / 0.2% unweighted on piano, which is more than the A3340 spec so if I can hear it I know that there is a problem.
As for the capstan bearing, oldvinydude's advice is what I do too. The A3340 capstan is a plain bearing so there is no part to change there, just cleaning and lubricating every so many years. Note that on my A3340 the idle motor applied enough torque to stop the capstan shaft almost immediately once you had stopped spinning it by hand, I guess he means to do this with the belt removed.
To detect soft rubber, all you have to do is press the end of a fingernail against the surface. Rubber in good condition does not show any trace, while aging rubber that has gone soft shows a mark that disappears quickly. If this happens, you can try rejuvenating it with naphta (aka lighter fluid) or a more specialized compound (I have a can of AF Platenclene for this). Apply and rub gently until the soft outer rubber is removed and the fresh rubber underneath appears. This method does not always work however, and your best option is usually to have your pinch roller re-rubberised, or to get a new pinch roller depending on the cost.
You can also detect an aging pinch roller by its symptom, which is an elevated wow & flutter. This is easy if you have an W&F meter, but if you don't have one you can use a computer with a sound card and dedicated software like WFGUI (free) or the Nakamichi T100 emulator. I won't insist on these as there is an easier and free solution, which does not measure the W&F but allows you to check rapidly whether your recorder has a W&F high enough to be a problem. Record a couple of minutes of piano, and play it back. If you can feel the flutter, then you know that you have a problem and a bad pinch roller is the usual suspect. Why piano? Well, it is by far the most sensitive instrument to flutter: voice or a continuous tone don't show it nearly as easily. The threshold of audibility varies from person to person, but personally I can consistently detect 0.1% weighted / 0.2% unweighted on piano, which is more than the A3340 spec so if I can hear it I know that there is a problem.
As for the capstan bearing, oldvinydude's advice is what I do too. The A3340 capstan is a plain bearing so there is no part to change there, just cleaning and lubricating every so many years. Note that on my A3340 the idle motor applied enough torque to stop the capstan shaft almost immediately once you had stopped spinning it by hand, I guess he means to do this with the belt removed.
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