[Drake] TR-7 Transmitter Alignment

[GGLL]

    Hello, are the final stage transistors the original ones?. I've 
recently done a complete repair and re-alignment of a TR-7; final pair 
was original but I had to replace the driver pair, with 2SC1969; also, a 
pre- driver (2N3563, in the pre-driver board)  one with a MPSH10. Have 
no problem at all, 150 watts at 3.5 ... 120 watts at 10.
But, check the switching diodes in the high pass filter board (that's 
one located at the left, with the band change shaft passing in the 
middle, Xmiter RF goes from here to the pre-driver board), you may have 
one or more leaky or shorted which can cause all the trouble. They're 
three at the output (UM9401), and another three at the input (two MPN3404).
One sign of a leaky diode is that there could be some volts (instead of 
zero)  in the +TX line (coming through this diodes from the + RX line), 
and "switching in" not desired portions of circuit.
Fortunately, they're easily accesible from the top.

Good luck
Guillermo - LU8EYW.

N0DBX wrote:

> It's actually an "A" and has the later pre-driver board:  If I
> try to set up the predriver and ALC as the book says, I get
> nice power out on 10 and 15, but 75 and 160 go into oscillation.
> Even at low drive levels they oscillate.  40 tries to light up also.
>
> I can lower the driver pot to clean up the 3.5 band and everything
> stabilizes, but now I only have minimal power on 15 and 10.  20
> watts or so on 10.
>
> Any ideas on whether it could be an alignment problem or perhaps
> in the driver-final?
>
> N0DBX
>
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