You could indicate the Chassis series that is printed on the Mainboard.
In a Chassis CM405F diagram that according to the search results, would correspond to your model, indicates that the R204, which you mention, works on the ABL line.
Therefore, it is involved in the fault you describe and the value assigned to the R would be very high. If this is the case, the chassis matches yours and you need to rectify that value here is the diagram:
http://www.archivotecnicosaurios.com/descargas/tv/seccion_ordenada/10243_Chassis_CM-405F_Manual_de_servicio.pdf