Modifications for the Kenwood PS-50
PS-50 Improved Voltage Surge Protection
Trio-Kenwood Communication, inc.
Service Bulletin no. 914 (23-5-1986)
We have received a few reports regarding the loss of transistor Q4, resistors R2, and R3, and zener diode D4 on the AVR UNIT. Apparently a voltage surge on the power input might cause D4 to short. If this occurs the surge current thru resistors R2 and R3 could be high causing the failure of the two resistors and Q4.
On the AVR unit X43-1520-00 open or remove diode D4.
If you receive a unit with no output voltage check D4, R2, R3 and Q4. You should replace R2, R3, and Q4 if there is any sign of damage to any of these components.
This change applies to serial numbers before 7040001.
Time required for this change is 1/2 hour or less.