[TenTec] Titan amp problem....help!

[W0AH@aol.com]

Problem:  After 20 seconds or so the Titan input SWR increases to over 3:1 
from it's normal 1:1 SWR and afterwards is intermittant, sort of cycling, 
back and forth between a high SWR and a normal input SWR.  When my FT-1000 
exciter "sees" the high SWR, it, of course, drops the excitation power to 
practically nothing.  
    This problem turned up a couple of weeks after lightning damaged several 
pieces of equipment in my shack, but not the FT-1000 which was not connected 
to the Titan or an antenna.  I think an antenna was connected to the Titan.  
Both the FT-1000 and Titan were plugged into AC lines, but the circuit 
breaker for my shack was in the OFF position (the lightning charge still 
might have jumped across the breaker).
    Anyway, it took a while (first checking the antenna, coax, and switches 
for an intermittant) before I finally grasped the nature of the problem while 
running power from the Titan into a dummy load on several bands and watching 
the SWR of the FT-1000 fluctuate on all bands.   My guess was that something 
was heating up, but what? 
    I talked to Rick Long at Ten Tec who suggested I examin the low pass 
filters, the bias diode on the rectifier board in the PS, relay K3, the band 
switch, and components on the input bias board.  Since I am not an 
experienced technician, he suggested I send the Titan and PS to Ten Tec, 
which I hate to do if I can possibly fix it here.
     Today, I examined the Titan low pass filters and bandswitch, seeing 
nothing at all suspicious.  I have not examined the bias diode in the PS or 
K3.
     I also examined the bias board and found that R1 is obviously charred.  
Checking associated components with my multimeter, I'm reading aprox 2.85K 
and 8.5K across both D7 and D10 while in the circuit, whereas I'm reading 910 
ohms and 160K across similar looking diode D5.  Humm.
     Please don't make the mistake of believing I know what I'm doing or 
understand the circuit.  I wish I did!  It does appear to me that D7 and D10 
are damaged along with charred R1 which reads close to its normal 10K when 
cool, but obviously has been heating up and is damaged.
       Can some one suggest futher trouble shooting???
        I guess I have several options: 
1)     I could replace R1, D7, and D10 and hope that solves the problem. 
2)     I could follow the troubleshooting suggestions of a patient elmer from 
here on the Ten Tec reflector.
3)     I could call Ten Tec and see if I could return just the input bias 
board for repair or replacement and hope a new or repaired board solves the 
problem.
4)  Perhaps you can think of other alternatives?
       I would very much appreciate your input and suggestions.
Doug  W0AH   Woodland Park CO
        
      

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