What charset to use?

[OuesFa]

Hi,
Im trying to read non UTF-8 file, it's IBM 500 file but i can't find it in the charset list provided with the plugin so i tried "US-ASCII".
Here is my config file:
input{
file {
path =>...
sincedb_path => "/dev/null"
codec => plain{charset =>"US-ASCII"}
start_position => "beginning"
}
}
output{stdout{}}

It doesn't work.
What i don't understand is that i don't have any error message, logstash starts and does nothing.
on my terminal i have only this message : "Logstash startup completed"

Any help please ?
Thanks