[BC] Te st your wits on this

[Jerry Mathis]

On Thu, Feb 23, 2012 at 5:04 PM, David Senft <dsenft at rawlco.com> wrote:

>Saturday night, Feb. 18th, a BE FM 20T Tx burned up the inner filament
>contact ring. When the ring was replaced, the transmitter ran perfectly into
>the dummy load but would not fire into a Dielectric star-point combiner.
 
><snip>
>D.

OK, I'll take a stab at it  :)

1. A totally different transmitter (Bext Exciter) doesn't have the problem.
2. BE Transmitter has problem, even trying several different tubes.
3. Conclusion: Problem MUST be in the BE transmitter, but maybe **before** the final PA tube? Is the IPA in this transmitter something like a Delta RF "brick"? I've had some of these go bad. In one case, it was generating a *strong* harmonic clear up in the 800 MHz band.
4. If you haven't already cleared the IPA stage(s), I would check the outputs of any/all IPA and driver modules. *Also* check any jumper cables if there's an internal RF "patch" panel. Have had those go bad too.

Please let us know what you find!

--
Jerry Mathis