1. It has cuts (from the tone hole edge) or tears.zagzig said:Are there some general guidelines for knowing whether a pad in a cup is gone or not?
2. It is really soft and squishy (i.e. it should not have been born!)
3. It has irregular thickness (i.e. it should not have been born)
4. It has gone hard like concrete, (unless a leak light shows that it tis still sealing really well, with light key pressure.
5. The hardness makes it unacceptably noisy when it hits the tone hole
6. You are attempting to re-use it after it has been removed from a key cup.
7. It has not been supported evenly over its back surface, eg cardboard part-shims without full filler of glue.
8. As a result of any of the above, the pad resists being adjusted to seal well.
It is annoying when one thinks a pad is OK, then spends a long tome trying to get it to seal, and eventually giving up, replacing the pad, and finding that one can achieve a good seal within seconds. Assessment is not an exact science!I can only presume assessing pads is a central part of of the technician's practice.
"Nevertheless is there a rule of thumb which could help me save old pads as opposed to doing a complete repad? "
I think all of the above probably answers that. Vague, but as good as you'll get. Experience teaches, if at all in doubt, ditch it!