Old School Electronic Boards

You should hear 2 dings then start up sounds.  If not, what transformer are you using?  If these are older units you want a good pure sine wave transformer or a Z-1000.  I would raise voltage up to 14-16 and wait for the 2 dings.  Then lower to about 8V and see if the sounds come back.  Try a direction change and see if the engine moves with sounds.  If not.  Shut down and wait 15 sec.  Restart at high voltage again, this time lower and raise voltage trying to get the engine to advance to the next reset state.  You need to try to do a reset 18.  Best to follow the directions.  G