[1000mp] MK5 Transmit Problem

[Jim Martin]

I have damaged the tuner unit possibly by trying to tune my 80m inverted L
for some of the higher bands.
Symtoms are a burning smell and D6452 in the tuning unit was dry jointed.  I
have cleaned it up and resoldered it but I still have the burning smell and
when I TX into a dummy load the SWR fluctuates between 2:1 and off the
scale.
Can someone tell me what D6452 does?  It reads about 26/36k ohms in circuit
but overheats almost instantly with just a few watts of power.
Any pointers or thoughts would be appereciated. Is there a site to download
the service manual/circuit diagram from?
73
Jim