1938 Master Deluxe, stock, 4 post voltage regulator, standard generator.
On a short run, the ammeter suddenly pegged on discharge, so I hightailed it for home. Revving the engine moved the ammeter off of "pegged" discharge, but not into charge. When I shut down, the key & ignition switch were fairly warm.
Cleaned & tightened battery connections, starter, ground strap, and the 4 regulator posts/leads.
Still pegged on discharge and warm key & ignition switch when I started and ran for a couple minutes. Now revving engine doesn't move ammeter. Ammeter does center when key is turned off.
Any suggestions appreciated.

Update - It's the armored wire from the ignition switch to the coil that is really, really hot and making the key & switch just toasty warm.

The wire inside of the cable is shorting out.

Yep you need to take the switch apart and replace the wire.

It would appear that I have an original ignition switch; it's the crimped case model without backplate access screws I've seen on some. Is there an easy way to get it apart without totally destroying it?
Thanks!

Yes....you uncrimp the case. The case is pot metal so the metal is soft to work with, and you can uncrimp the case if you are careful.

Check your e-mail. I sent you some pics that might help.