On Aug 26, 5:24 pm, "George Kavanagh" wrote:
I'm in the process of removing parasitics in the final of a 6DQ5 75W
transmitter (1963 ARRL HB, pg 176), and am in need of source for 2+ watt
non-inductive reistors for parasitic traps in grid & plate circuits.
Sources for higher wattage carbon composition resistors seem to have dried
up. Can ceramic composition resistors, such as Ohmite's OX/OY series be
used? They are touted as "non-inductive". Please advise.

In several cases (can you say "choke fire in the final cabinet that
took out the parasitic suppressors too"?) I've replaced these with 2W/
3W/5W metal oxide resistors with no problem. I think I was using the
el-cheapo Xicons from Mouser.

When I've purposefully burnt low-ohm metal oxides (it's surprisingly
hard - the resistor literally has to glow red hot for it to happen!)
it is clear that while there is a spiral winding, that it's quite wide
and only a turn or two for the resistors in the low ohm range and that
the turns are extremely wide and fat. They could very well be lower
inductance than the original carbon comps.

In fact the original choke fire that took out the original parasitic
suppressors probably resulted from parasitic oscillation in the finals
(I always assumed so - drawing a couple hundred mA with no input, and
a bright blue glow from the final compartment, I always thought must
be some sort of parasitic!)

Tim N3QE