[AMPS] L7 Amp Questions

[Harry Brown]

I recently got an L7 Amp with a bad 3-500Z. The tube plate had shifted and
shorted to the grid. This caused the RF choke that Drake uses in the grid
to ground circuit to go up in smoke.

Does anyone know the value of the RF choke used and where they can be
obtained? I would also like to know where I might obtain a parts list for
the amp since the manual that I got with the amp does not have one.

Another question is on Drake's method of grounding the grids using RF
chokes and shunt capacitors to ground. The ampss that I've seen in the
Radio Handbook ground the grids directly. What's the
advantages/disadvantages of doing it the Drake way? Any harm in just
grounding them directly? 

And yet another question. I believe that one of the tubes is OK so I really
only need one tube for the amp. The write ups I've seen on using two of
these tubes says they must be matched. How closely do they need to be
matched? Does one just check for idling current and verifies that each tube
draws the same current +/- some percentage, does the grid current have to
match within some amount, or what?

73, Harry, W3IIT


                           Microwave Update/Hamarama 2000
                        September 28, 29, 30/October 1, 2000
                                  PHILADELPHIA, PA.
                                FOR INFORMATION VISIT
                      http://www.ij.net/packrats/MUD_2000/mud.html

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