I've seen cases where a radio had a reverse biased diode protecting the B+ input and when the radio was wired up wrong, it not only took out the protecting diode but most of the other solid state components.
Takes about 5 seconds to SCROLL DOWN the OH2FFY web page on FT-707 power & AVR,
view schematic for FT-707 POWER DISTRIBUTION and answer that conjecture.http://hfdxer.x90x.net/ft-707_avr/ft707-02.html
Many color photos by OH2FFY for the novice tech to see and compare to
Service Manual pictorials and schematic diagrams.
AVR - Automatic Voltage RegulationA common acronym used by Japanese radio designers for DC-DC conversion and
DC voltage regulation functions in mid-1970s or later solid-state transceiver or DC power supply.