This invention relates to a variable resistor unit for a high voltage (hereinafter referred to as "high-voltage variable resistor unit"), and more particularly to a high-voltage fixed resistor for a high-voltage Variable resistor unit.
In the art, there has been conventionally used a high-voltage variable resistor unit commonly called a focus pack for controlling a focus voltage of a cathode ray tube (CRT) or a screen voltage thereof. The conventional high-voltage variable resistor unit is generally mounted on a transformer casing of a fly-back transformer. A high-voltage variable resistor unit of the type of being decreased in output voltage is conventionally constructed in such a manner that a resistance pattern for a variable resistor and a resistance pattern for a fixed resistor called a bleeder resistance which is connected in series to the resistance pattern for the variable resistor are formed on a single substrate. Unfortunately, the high-voltage variable resistor unit of this type, when the voltage is increased, tends to cause discharge between the resistor patterns and/or between each of the resistor patterns and an electrode. In order to solve the problem, an approach that the fixed resistor called a bleeder resistor which is arranged on a high voltage side is received in another receiving section while being mounted on another insulating substrate is employed.
Conventionally, a holder is used for receiving the insulating substrate on which the fixed resistor is formed in the insulating case. For example, Japanese Utility Model Application Laid-Open publication No. 116005/1991 discloses a high-voltage variable resistor unit including a holder which is adapted to hold an end of an insulating substrate for a fixed resistor while keeping a large part of the substrate exposed. The holder is fixed in an insulating casing through a fitting structure. Then, the insulating casing is combined with a fly-back transformer, followed by being charged therein with thermosetting insulating resin for molding of the fly-back transformer. Use of the holder wherein a large part of the insulating substrate is exposed exhibits an advantage that the insulating substrate as well as the transformer is molded by the insulating resin. However, it has a disadvantage that occurrence of any crack in the insulating resin cured often causes discharge to occur at a high-voltage region on the insulating substrate. In view of the disadvantage, a holder which is formed into a one-side-open hollow shape so as to receive an insulating substrate therein is proposed, as disclosed in Japanese Utility Model Application Laid-Open Publication No. 32504/1992. In the Japanese publication, an insulating substrate on which an input lead wire and an output lead wire are respectively connected to electrodes in a pair each arranged on each of both ends of a resistance pattern for a fixed resistor is received in a holder, which is charged therein with insulating resin for molding, resulting in providing a high-voltage fixed resistor. The high-voltage fixed resistor thus formed is then received in an insulating casing for a high-voltage variable resistor unit.
The input lead wire is electrically connected to an output terminal of a fly-back transformer through a connection means. A lead wire, a connector terminal or the like may be used for the connection means. Alternatively, the connection means may be constructed by inserting, into an electrically conductive rubber terminal used as an output terminal of the fly-back transformer, a wire-like terminal to which the input lead wire described above is electrically connected. Japanese Utility Model Publication 18904/1985 discloses use of an electrically conductive rubber terminal for electrical connection between a fly-back transformer and a high-voltage variable resistor unit. A wire-like terminal is fixed on a holder.