Hello, Pat -- The 1mH choke was not defective. It smoked for a
reason -- i. e., too much grid current. However, the surge in grid
current was probably not caused by operator error. All tubes have a
small amount of anode-to-input feedback-C. This is insignificant at
HF, but not at VHF. It might be a good idea to check the tube whose
choke smoked for a filament-to-grid short since high grid current
exerts lateral stress between the grid and the filament. I would
replace the smoked choke with a 0.25w to 0.5w carbon resistor that has
a similar # of DC ohms. 20 - 30 ohms is typical. However, to protect
the resistor from 10m RF, add 1000 or so pF to the existing grid bypass
C. In the event of an oscillation condition, the small resistor will
open and hopefully protect the tube from failure. cheerz
On Jun 19, 2004, at 11:04 AM, N7uvh@aol.com wrote:
does anyone know of a good online retailer of the 1mh rf choke used in
the
sb-200 at the bottem of the z500 tube. I have replaced my recifiyer
board with
harbuch and looks like I have smoked a choke. I found one place but
was 22
buck each.
tnx
Pat
n7uvh@aol.com
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|