Are the batteries on proto 1 &2 the same?. Thanks for your help
Proto 1 takes a 9 volt battery. The early proto 2, AKA the 5 volt version also takes a 9 volt battery. As far as I know, the later proto 2, AKA the three volt version takes a different battery.
Yes Proto-Sound and PS2 5V systems use the same battery that resembles a 9V battery. The later PS2 3V system uses two cased batteries that resemble two wrapped AA batteries.
For 3V, you'll find these, the replacements come in NiMh with the same form factor. There are also smaller 3V packs for the 3V boards.
The early 5V boards and older Protosound 1 boards take 9V batteries.
If you find one of these in your locomotive, I suggest you replace it immediately!