| 摘要 |
PROBLEM TO BE SOLVED: To attain the continuous playback operation of a playback element for a long period under the high temperature environment by allowing the continuous supply of the operational bias when the element temperature of the playback element exceeds the upper limit of the normal operating temperature. SOLUTION: The temperature coefficient showing the relation between the element temperature of the playback element and the element resistance, and the limit element temperature showing the upper limit value of the element temperature which is the condition to enable the playback element to normally perform the playback operation during the preliminarily determined time, are kept in a storage means. The element resistance of the playback element is measured by an element resistance measuring means. By a bias control means, the element temperature of the playback element is calculated on the basis of the element resistance and the temperature coefficient held in the storage means, and the value of operational bias in an operational bias supply means is changed and operational bias is continuously supplied so that the calculated element temperature becomes equal to the limit of the element temperature or lower.
|
