When we had alt failure (didn't actually know what precise fault was) the V/R was changed and on the next flight alt failure again, this time the alt was changed and no further probs.
If you do get off with a well charged battery and said Ta-Ta on the radio, and are quite happy to lose your elec gyro's, do as we did, turn the master off until required, It's not a real drama if you have decent VMC and charged up GPS's.....