[MrFixr55]

Does your B+ still drop to near zero V when set warms up? You need to fix that before going anywhere else. If this is happening with only the rectifier installed, then troubleshoot by disconnecting all loads then adding them one at a time. Sounds like a cap shorts when things heat up. Check C18, a 100pF mica cap for shorts. Check the output and band switches as B+ may go to these switches.

Hope this helps.