[TenTec] Fried Titan, cont'd

[K6JEK]

I fixed the fried control circuitry but it didn't die fast enough to 
save the tubes.  Definitely fried were Q1, cathode bias control 
transistor, R19, the emitter resistor on Q1,  R15,16,17, shunt for the 
plate current meter.  Probably fried  were D2, 8.6V Zener in the 
cathode bias circuit, D5, 5V Zener.  Maybe fried:  the other four 
transistors on the bias board.  John, the service guy at Ten-Tec, said 
he'd replace every transistor on the board.   I did this.  They cost 
just about nothing.  I didn't test any besides Q1 to see if any were 
gone.  Two things I expected to be cooked which weren't:  D13 --  B- to 
ground in the power supply; U1A, op amp that drives the meters but gets 
its signal across the cooked emitter resistor.  The juice was enough to 
fry a 4.7 ohm resistor but not the op amp across it.  How about that?

Does anyone know where the best deals on 3CX800A7's are?  I'd even buy 
pulls if I knew they weren't dead.

Jon

On Jan 20, 2005, at 9:31 PM, K6JEK wrote:

> I cooked my Titan I this afternoon.  I managed to route the output of 
> my homebrew AM transmitter into the Titan input when the Titan was on 
> and ready to amplify.  It seemed to think that 300 W carrier with 1200 
> W peak was more than it wanted.  POW, smoke, dark.  Not much smoke, 
> just a tiny bit.  It did blow a fuse but when I replaced the fuse, the 
> grid current meter pegged on power on even before the B+ kicked in.
>
> I'm now poking around on the bias board where there seems to be a 
> fried 1/4 W resistor.  It will be grand if that's all the damage.
>
> Any advice?  Have any of you ever done anything this witless?
>
> Jon
>
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