Hello George
Problem: faulty exciter diode in the alternator.

Answer: Replace the diode pack.

Problem: Replaced the Bosch 9 x diode plate with Bosch 6 x diode plate, multiple Bosch 6 x diode plate failures.

Question: Can anyone comment on what’s been happening?

Answer: Bosch 6 x diode plate is one third the capacity of the Bosch 9 x diode plate.

Solution: Need local source for the Bosch 9 x diode plate or friend to help find one.

__________________
ASE Master Mechanic

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D

https://www.boldegoist.com/