Thanks for the reminder about the cooling, Evan. The source of the arc is
difficult to see in the video, but if you look through the plastic bubble that
forms the back side of the plate current meter, you can see the source of the
arc, in the Plate tuning capacitor.
73, Bill
--- On Wed, 5/19/
Caution is in order when testing the amp for any significant period of time.
With the top off, the base of the tubes will not get adequate cooling. Even
though there are slots on the bottom side of the cabinet, with the top off most
of the air to cool the tubes will come from above with little
> You might want to check the impedance of your Heathkit Cantenna.
===
Also, the brass clamps on each end of the Cantenna resistor have a tendency
to become (age or work hardened) brittle and break causing an intermittent
or an open.
K7DFW
..._._
__
You might want to check the impedance of your Heathkit Cantenna. Early
models did not have a coating on the resistive element and tend to
change characteristics over time. I had one that doubled in resistance.
Much more than that and you may be beyond the L7's ability to tune.
73,
Bob AD3K
From
Thanks, John. I noticed the black dot as well and it drove me crazy trying to
figure it out. After many attempts to duplicate, it turned out to be the rotor
on the Load cap. It disappears a moment before the arc because I was turning
that control to the left at the time of the arc. That is w
In a message dated 5/18/2010 10:38:27 P.M. Eastern Daylight Time,
billdz@yahoo.com writes:
http://www.youtube.com/watch?v=iJRyNQnkEWA
I notice 2 things:
The tube nearest the transformer is displaying a red plate before the tube
nearest the side panel and it appears to be more than
Date: Tue, 18 May 2010 23:08:20 -0700 (PDT)
Bill,
I agree that you probably need to polish the plate cap, but there's something
nagging at me that's saying the root cause of your problem may be a VHF
parasitic. These can be nasty to isolate (some folks can find them with a GDO
but I've never b
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