[Early_S_Man]

Don,

Losing power from an ignition switch is not necessarily a 'short' ... more often it is an intermittent 'open' condition!

However, from your starting sequence description ... it sounds like your battery may only have a 'surface' charge, and after one cranking attempt, battery Voltage is too low to operate radio, CDI, headlamps etc. Hence the ten minute cycle of 'lost' power. The capability shown by your battery is not that of a fully-charged battery by any means! I strongly suggest that you need to charge your battery with a 6 - 10 Amp charger, overnight, or longer!

The electrical portion of the ignition switch may be faulty. It can be replaced as a separate part. Not really the suspect at this point by my judgement at this point, though.

964-613-012-00-M100 Ignition Switch - Electrical Portion only, 911 (1974-89) Brand: Genuine Porsche $58.75

You can, of course, verify that different circuits are losing power when the switch is operated ... with a multimeter and long test leads. This needs to be done after the battery is fully charged, of course!

BTW, it is normal for radio and lights to be switched off when ignition switch is in the 'Start' position vs the 'Run' or 'On' position.