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在发射机发生的故障中,有部分是由上电及关机延时电路直接造成的。其主要表现是延时时间渐渐变短,直接影响发射管的使用寿命;或是延时电路热稳定性变差,造成不必要的下高压、偏压等,影响播出率。为此,笔者设计了一种完全不同的上下电延时电路,也就是用廉价的EPROM和精度很高的石英钟模拟电路替代原阻容延时电路。 (一)电视发射机上下电延时程序以成都电视设备厂TDF-10K-I型发射机为例,该系统的开关机程序如下: 开机—→风机工作—→灯丝一档工作—→延时40s—→灯丝二档工作—→延时10s—→偏压工作—→延时3min—→高压一档工作—→延时10s—→高压二档、帘栅压工作—→延时20s—→激励器功放
In the transmitter failure, some are caused by the power-up and shutdown delay circuit directly. The main performance is the delay time becomes shorter, a direct impact on the life of the launch tube; or delayed thermal stability of the circuit worse, resulting in unnecessary high pressure, bias, etc., affect the broadcast rate. To this end, I designed a completely different power delay circuit, which is the use of cheap EPROM and high precision quartz clock analog circuit to replace the original resistance delay circuit. (A) television transmitter power-down delay program To Chengdu Television Equipment Factory TDF-10K-I-type transmitter, for example, the system switching process is as follows: boot - → fan work - → a filament work - → delay 40s- → filament second gear work - → delay 10s- → bias work - → delay 3min- → high pressure a file work - → delay 10s- → high pressure second gear, the screen pressure work - → delay 20s- → Exciter amplifier