[SBE] Continental 816

[Vic Jester]

Barry - Some things to look at: (Johnny's comments included)

1)  Check the Zeners that are used to create the IPA Screen Voltage.  They're in TO-3 cases on the side of the IPA assembly.  It's not uncommon for them to fail.

2)  Check the IPA Tubes - getting good 4CX250's is a challenge today.  -- And these are mounted horizontally, so are prone to internal shorts (one of the reasons for the Zener failures).  If you need these we have several complete tube IPA boxes on the shelf from SS conversions.

3)  Consult the manual - use the tuning procedure.  Put the radio into a dummy load, turn the PA Screen Voltage breaker off, and go through the tune up procedure from IPA input to PA Grid input.  It >may< be that the newer 4CX250's have enough difference that the IPA is grossly out of tune.  

4)  The "efficiency" control (capacitor on the bottom of the PA Tube socket) is very sensitive.  There's sweet spot and it affects just about all of the IPA and PA tuning.  IIRC, it's even more sensitive on the tube type IPA radios.

5)  Talk your employer into purchase of a solid state driver conversion kit.  We've installed, at last count, five here.  Again, getting good 4CX250's is difficult...  The 816 is one of, if not THE, best transmitters ever built.  With TLC it should "run good, and last a long time".


Call me if you want.

Vic


>The problem:  I am not getting enough power out of the transmitter .... Only 80% with it running at full blast.  The final is new and good and tunes well. 
>
>I'm fairly certain it's driver-related. 
>At first I thought it was just bad 4cx250b tubes...They were old.  I Replaced them but still have the same results. Both tubes are operating and seem balanced.  I've got a good match from the exciter into the driver stage and the driver plate tunes into the final, although PA grid current is low (of course).