新型录像机故障维修讲座 第十五讲 定时器／操作开关电路维修（下）

上一讲我们介绍了定时器／操作开关电路的基本原理和故障检修概要，本讲对该部分电路的ｎ个维修实例进行分析。例１机型：日立ＶＴ－Ｍ７７７ＥＭ（ＤＨ）故障现象：插上电源插头后多功能显示屏无任何显示，但可见显示管灯丝点亮，所有按键均失效。分析与检修：这种故障可能涉及到多种原因，首先应检查电源部分插件ＰＧ１的各组输出电压。由于该机采用开关电源电路，多功能显示屏（管）的灯丝电压取至开关变压器脚⒂、⒃（经Ｄ１３和Ｃ２３整流滤波），通电后可见灯丝点亮，说明开关电源振荡电路基本正常；若检查ＰＧ１输出电压（除受控于系…     

单相电源供电的平滑加电灯丝电路

本文介绍一种单相电源供电的平滑加电灯丝电路。使用这种电路可延长发射机大功率电子管的寿命。     

中波GZ-50Ⅱ型发射机高前级阴极回路与灯丝回路的接入原理与维护

ＧＺ－５０Ⅱ板调机的高前级使用Ｆｕ－１００电子管，它的阴级是旁热式的，但阴极与灯丝有一公共引脚，这一点与机中其它电子管是不同的，使得其阴极回路与灯丝回路的接入方式与众不同。如果在维护过程中因忽视了这一点而将阴极回种与灯丝回路的接入点搞错了，将会使发射机输出载波中调制上一个５０Ｈｚ（灯丝电源频率）的包络，严重影响整机信噪比（达不到５３ｄＢ的乙级标准），但因故障较隐蔽而难以查找。本文通过对电路原理的分     

JEM－200CX电镜故障维修小结

ＪＥＭ－２００ＣＸ电镜故障维修小结洪建明赵小宁（南京大学现代分析中心，南京２１００９３）现将我中心ＪＥＭ－２００ＣＸ透射电子显微镜使用十一年来故障维修情况作一小结，供同行们参考。（一）故障灯丝寿命缩短。一般灯丝在正常情况下可使用１００～２００小时。但...     

GSUF—1—型发射机故障检修

我台使用的分米波发射机是鞍山广播器材厂引进美国TTC公司XL1000MU发射机，进行消化吸收开发出的国产化产品，该机采用逻辑控制，发光二极管状态指示，自动、手动开关机控制，直接显示各系统的工作状态，灯丝电压分两档上，保证电子管使用寿命，采用了视频信号自动开关机电路等一系列先进技术。多年来在使用过程中，灯丝电源调整板曾出现过一些较特殊的故障，现分析如下。1故障现象（1）开栩而热时间到，风栩不抵．予执时间无限长，且灯丝电压只有1．SV。（2）整机加电后，无论有无开机信号，灯丝电压为6V以上（6.3左右），且风机不停。…     

中波发射机瞬间停电自启动电路

中波发射机瞬间停电自启动电路杨伟方（河北省广播电视厅６６２台）本电路的功能是在瞬间停电后，能使发射机冷却系统、电子管灯丝、低、中、高压依次上电，２秒钟内恢复中断的播音；停电时间超过设定时间（１０ｓ），不执行任何动作，另有停电报警电路报警，由人工处理。...     

H—300电镜灯丝的制作方法

目前,我国已引进为数不少的H-300电镜,但随主机配备的原装灯丝数量有限,灯丝的寿命也不长。鉴于上述情况我们利用原有的灯丝座制作了新灯丝,以不断补充灯丝的消耗。经实践验证,我们自制灯丝的性能除与原装者相同外,还成倍地提高了灯丝的使用寿命。日本灯丝的寿命最长为60小时左右,一般仅有40～50小时,而我们自制灯丝的寿命最长可达120小时左右,一     

电子显微镜灯丝专用保护器

为保证图象的清晰度，电子显微镜的灯丝多采用Ｖ形结构，并工作于饱和状态，因此灯丝寿命一般只有３０～５０ｈ。专用保护器具有Ｖ形阻－温特性，能有效地防止冲击电流的产生，抑制过载电流，使灯丝寿命至少可延长到６０～８０ｈ。     

彩电灯丝电路常见故障分析与检修

彩色显像管的灯丝电压值通常为6．3V，灯丝电压通常由行输出变压器提供，电路相对独立。在伴音正常，屏幕无光栅或工作过程中出现慢性时亮时熄等故障时，检修应从灯丝电路入手。     

乐华TC511─2PD彩电行、场扫描电路故障两例

乐华ＴＣ５１１─２ＰＤ彩电行、场扫描电路故障两例１．行扫描电路故障现象开机后可听到开关电源吱吱声，但图象、伴音均无。分析及维修打开后盖，通电后测量电源电压基本正常，约１０８Ｖ，继而测行输出Ｑ＿（５５１）集电极电压亦为１０８Ｖ，而灯丝不亮，基色矩阵电路...     

Influence of carrier lifetime distribution on the current filament in high voltage diode

The current filament caused by strong dynamic avalanche during reverse recovery of a high voltage diode under extreme overstress conditions is an important factor of the device failure. The influence of carrier lifetime distribution on the current filament during reverse recovery of the high voltage diode was analyzed by the comparison between the uniform carrier lifetime distribution and the local low carrier lifetime distributions, and the variation process and the inhibition mechanism of the current filaments in diode were discussed. Electrothermal simulations show, how the local low carrier lifetime distributions can provoke the evolution of the anode-side current filaments and the appearance of multiple cathode-side current filaments. It is deduced that the low on-state plasma at the anode side is supposed to be the essential reason for the inhibition of the current filaments.     

真空在节能荧光灯中的重要性

在节能荧光灯的制作工艺过程中,真空度将是决定灯管内在质量的重要因素。本文对灯管制作过程中的灯丝(阴极)的加工处理;排气规范中分解、激活的要求和排气(充气)设备设计制作的改进等方面提出理论依据,并已在生产实践中得到了明显的效益。     

节能荧光灯管寿命的探讨

本文研究了节能荧光灯管整个生产过程中影响其寿命的因素，除了保证一定的真空度和真空卫生外，选取优质荧光粉，改进灯丝结构，采用质佳的电子粉，严格控制涂粉量，选取适当的充氩气量，对灯管的长寿命，高可靠是极其重要的。     

推荐使用—透射电镜灯丝发射自动控制器

本文介绍了透射电镜灯丝发射自动控制器的原理和特点。本控制器的使用,不仅可简化电镜操作,还可延长灯丝的使用寿命。     

Estimation of Weibull Shape-Parameters for Two Independent Competing Risks

This paper presents a technique to estimate Weibull shape parameters of life distribution of two components in a series system. The data consist of lifetime of the system only, that is, it is not known which component caused the system failure. The relations among cumulative hazard functions of the system at virtual observation limit are used for estimation. This technique is useful for 1) analysing this common kind of life-test data, and 2) estimating parameters of the smallest extreme value distribution. A numerical example including the experimental data on electron tubes is discussed briefly.     

Analysis of quantum conductance,read disturb and switching statistics in HfO2 RRAM using conductive AFM

Most studies on resistance switching have been carried out at the device level with the standard electrical characterization setup, which allows for effective automated reliability test and extensive characterization of the lifetime of an RRAM device. However, it is equally important to be able to probe the switching phenomenon at the nanoscale so as to improve insight on the bias-dependent kinetic behavior of the filament during multiple reversible breakdown and recovery cycles. This study aims to do just that by probing HfO₂ blanket films (~ 4 nm) with a W bottom electrode using an ultra-sharp Pt-wire conductive AFM (CAFM) tip with an areal resolution of ~10–20 nm at ambient conditions. The use of the CAFM allows for a more reliable assessment of single filament evolution behavior as possible multiple filamentation events (common at the device level) are rare for such small probing areas. The role of oxygen vacancy induced filaments is studied here by using low compliance setting and moderate voltage levels, ensuring operation in the sub-quantum conductance regime. Our results show good repeatable switching trends and also provide insight on the quantum conductance phenomenon in oxygen vacancy based filaments. The read disturb trends in switching are investigated for the high resistance state (HRS) and the impact of tip-induced mechanical stresses on forming lifetime is also presented, which could serve as a motivator for further studies on non-volatile memory (NVM) reliability for flexible electronics devices and system on chip (SoC) applications.     

Piezoresistive Sensors Based on Carbon Nanotube Films

Piezoresistive effect of carbon nanotube films was investigated by a three-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapor deposition. The experimental results showed that the carbon nanotubes have a striking piezoresistive effect. The relative resistance was changed from 0 to 10.5 X 10-2 and 3.25 X 10-2 for doped and undoped films respectively at room temperature when the microstrain under stress from 0 to 500. The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220 and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35 ℃. The origin of the resistance changes in the films may be attributed to a strain-induced change in the band gap for the doped tubes and the defects for the undoped tubes.     

应力诱导碳纳米管电阻的变化

利用三点弯曲法研究了掺杂和末掺杂碳纳米管薄膜应力诱导电阻的变化。该研究中所用的碳纳米管是用热灯丝化学汽相沉积法合成的。实验结果表明 ,碳纳米管有显著的应力诱导电阻变化的效应。当应力从 0 .2GPa增加到 1GPa时 ,膜的电阻相对变化从 7%增加到 11% ,而非掺杂的薄膜电阻变化小于掺杂膜的情况。电阻随应力变化的原因也许是带隙变化 (掺杂 )和管之间接触电阻变化 (非掺杂 )所致     

微通道板及其真空处理工艺研究

本文主要介绍几种新型的微通道板（ＭＣＰ）。同时简单叙述采用热烘烤和紫外光照射清洗技术对ＭＣＰ进行真空处理的工艺研究过程和结果，采用这种ＭＣＰ作为电子倍增器的光电倍增管，其性能稳定，寿命达１０００ｈ以上。     

Spatial-Harmonic Magnetrons with Cold Secondary-Emission Cathode: State-of-the-Art (Review)

Spatial-harmonic magnetrons with cold secondary-emission cathode are efficient high-power sources throughout the millimeter wavelength band. In this paper, resent advances in design, modeling, and fabrication of such magnetrons are described. Low-voltage magnetrons, sub-THz tubes, and magnetrons with metamaterial anode structure are described to illustrate these advances. The issue of the lifetime of the magnetrons with a cold secondary-emission cathode is also addressed. The main problems related with the usage of an auxiliary cathode in such tubes are considered and alternative solutions are discussed. Potentials for further improving the performance of spatial-harmonic magnetrons are analyzed as well.