Video source of Test pattern for TV or monitor repairing


The amateur has no any specific tool to deal with test pattern, however, today’s very low price DVD or VCD could be used as low-cost solution. Google is good tool to be used for searching, there are many pictures of TV test pattern.http://en.wikipedia.org/wiki/Test_cardFile:Philips PM5544.svg

File:Telefunken FuBK.jpg

 

The picture of TV test pattern can then be captured by uses the computer with screen capturing software, later on, such video file is used to burn for a DVD/VCD. Simple to konw this DVD/VCD is able to play, the video source of TV test pattern is ready to goes with, easy and low cost.

A proof of this idea and it works for my project, the screen capture about one minute, the file size is almost 1.5M in AVI format, such AVI file is about to burn to a CD-RW for test whether it is really works, Nero burner is used for the purpose, insert this AVI file repeately until the disc is full. My own TV test patten video source is ready.

see the test shot from the TV screen, it works.

tr0016371

Notice about this TV set, the test patten from this TV set display, black & white has problem and grey scale was so bar, is it possible the problem for this defective TV set ?! do not know yet, but soon and later, it will be able to confirm on this. the question is, theory is only applicable when the specific schematic of the fault TV set is available.

視頻鉗位電路
http://www.chinaecnet.com/big5/tech06/te060464.asp
quoted below in case their server down

在 模擬信號中包含有交流分量和直流分量,當信號通過交流放大器處理時,由于放大器存在耦合電容,所以信號在通過這些耦合電容時會丟失直流分量,對于音頻信號 來說,直流分量對我們沒多大意義,丟失了也沒關系,但對于視頻信號來說則不同。當視頻信號丟失了直流分量后,圖象的黑電平(即同步電平)將不能固定在同一 電平上,同步頭將隨圖象信號的內容產生變化,如圖Q-1所示,從圖中可見,同步頭不能對齊。為了使同步頭對齊(同步頭固定在一條電平線上),使之不受圖象 內容的影響,必須要恢复它丟失的直流分量,這就用到鉗位電路,電路如圖Q-2。

當輸入信號在同步脈衝作用期間,信號加在D1兩端使D1正偏而導通,b點電位等于C點電位(C點電位是由R2、W、D2-D4、R3分壓所得)。同時C1 被充電,因D1的導通使其充電時間常數非常小,很快就充電完畢。同步脈衝過后C1所充的電壓將加在D1上使D1反偏而截止,C1通過R1放電,但R1阻值 很大,所以其時間常數遠大于行掃描周期,此期間C1兩端電壓几乎不變,也就是說b點電位始終等于C點電位,如果此時有一個幅度較大的同步頭信號到來,那么 D1將又被正偏而導通,b點電位還是等于C點電位,因此視頻信號的同步頭將被鉗定在C點的電位上,如圖Q-3所示。調整W可改變C點的電位。

為了保証C1在放電期間的時間常數足夠大,所以OUT接入的阻
抗必須要足夠大,可使用一級射隨器或使用場效應管。電路中的D2–D4起著穩定C點電位的作用,當溫度升高時b點電位將升高,因二极管有負溫度特性,當溫度升高時其壓降也降低,從而穩定了C點電位。


本文摘自<<廣州電子技術网>>

Youtube is well known as a video server. there is Youku in China, a lot of video tutorial for TV repairing or for other applicanes

http://v.youku.com/v_playlist/f875809o1p14.html

http://v.youku.com/v_playlist/f944903o1p3.html

There is a FTP server, alot of service manual of TV set, possible the Russia hosted, no really help if a specific TV set model is expected, but it is useful for reference and llearning,

http://download.qrz.ru/pub/hamradio/schemes/tv/

some of them are filed as *.exe, in case you are not sure whether it is safe to decompress within your PC, just put it up to the on-line virus check,

http://www.kaspersky.com/virusscanner

This is another web page, alot of schematics for arcade machine, some basis of electronics as semiconductor, transistor’s appliaction & configuration,

http://arcarc.xmission.com/PDF_Electronics/Semiconductors%20Part%202.pdf

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