xiaolabaDIY 的部落格

今天參觀台中的九二一地震教育園區, 碰到10個自由行的祖國同胞. 聽他們對話, 說沒去汶川看地震後果, 卻來了台灣看, 覺得是走馬觀花. 聽口音像是上海的同胞. 所謂飽人不知餓民飢, 也是他們福氣, 沒碰過最好, ABL = about beautiful life ?


http://tw.myblog.yahoo.com/jw!fOLtnSyFFRnU173VUFcnug--/guestbook
想不到有幸在網站上遇到這位翁先生, 雖然素未謀面, 但得到其提點, 所以繼續學習. 人家1990年設計的東西, 俺今天2009年才來學習原理, 實在有點汗顏, 而且 CRT 都要退潮了. 回文中提到 ABL, 第一次聽到 ABL?! ABS 就看很多 (ABS塑膠, ABS煞車)...

雖然沒有聽過什麼是 ABL, 不過大概今天有GOOGLE, 應該不太難去找到相關的資訊,

用中文查 ABL電路
http://www.google.com.tw/search?q=ABL+%E9%9B%BB%E8%B7%AF&sourceid=navclient-ff&ie=UTF-8&rlz=1B3GGGL_zh-TWTW209TW209

用英文查 ABL schematic
http://www.google.com.tw/search?q=ABL+schematic&sourceid=navclient-ff&ie=UTF-8&rlz=1B3GGGL_zh-

很快地檢示搜尋到的結果, 看看到底人家行家們所說的 ABL 是啥東西, 就算不是這個問題, 機器也修不好都沒關係, 起碼也會學到 ABL 三個字在電視 / CRT螢幕這個行業裡的意思. GOOGLE 用多了, 自然也會很快地找到很多豐富的資料, 沒學過也不重要, 買書錢都可以不用花. 得到兩個比較可參考的網址如下,

http://zhidao.baidu.com/question/82612745.html
http://www.noahtec.com/electronic-repair-articles.htm

結論是,



ABL = Automatic Brightness Limit, 自動亮度控制

源頭是 FBT 的其中一個腳
最終的目的地是控制 IC 的 ABL 輸入, 對應這個電視機的 IC 是 AN5156K 的 33 腳.

有了這些基本的資料, 就可以看看 PCB 把相關的零件號碼和數值都找出來, 只要不是 IC 壞, 都可以簡單確認是否有問題. 今天學到的是 ABL.到此為止. 需要向這些前輩們說聲感謝, 不管能不能 FIX 這個電視, 因為每次都有心得和收穫. 放假有空就可以繼續玩玩.

待續.........




copy from the following link, in case the server is going to off in some day future, I can still have the copy to learn from.
http://www.electronicrepairguide.com/flyback-transformer-monitor.html
http://www.noahtec.com/flyback-transformer-abl-line.htm

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       Fast and simple way to find the abl pin

Whenever there is a complaint about monitor contrast problem i will check on the flyback transformer ABL (automatic blanking limiter) circuit. Sometimes a weak picture tube might caused contrast problem. If the picture tube is good, i will go straight to the contrast circuit. The question is how do we find where the contrast circuit located? Simple, if you have a datasheet for the video pre-amplifier ic, definitely you can find the contrast pin. For LM1203N video pre-amp ic the contrast pin is located at pin 12. Replace this ic or trace from this circuit to find the cause of the contrast problem.

From experienced, usually capacitors shorted and resistor turned into high ohms were the caused of the problem. A video pre-amplifier can also be defective. To confirm whether is circuit or ic problem, just solder out the contrast pin and switch on the monitor. If the monitor display normal picture (contrast ok) then suspect the abl line circuit. If it remain the same (dim contrast) replace the video pre-amp will usually solve the problem.

The contrast signal came from one of the pin (leg) of a flyback transformer which we called it as abl pin. Many technicians have the difficulty to trace the abl pin because usually a flyback transformer consist of around 10 pins. Some pins are B+, GROUND, AFC, ABL, X-RAY PROTECT, VCC, to HOT, HEATER, horizontal centering and etc. But there is one and simple way that i'm gone to show you how to locate the abl pin. Use two analog multimeters set to x10kohm range. Connect it in series (+ probe to - probe) and measure the flyback transformer from anode (the red cap) to all of the pins under the flyback. You have to desolder all the
pin or just remove the flyback from the mainboard in order to get an accurate reading.

If either one of the pin shows a diode reading that is the abl pin. The reason we use two multimeters is because the flyback circuit internally have couple of high voltage diodes connected in series. If you have a schematic diagram or any monitor or television troubleshooting book, you will see that the internal flyback diode are connected in series. By connecting two meters the ouput from the probe is around 24 VOLTS which is enough power to check the flyback internal diodes. After you have determined the abl pin, you can proceed to follow the line and find the bad components that cause the contrast problem.

Television or tv flyback transformer generally have the same design compare to monitor flyback. Whether it is a montblanc flyback transformer, rca, mitsubishi or sony flyback the checking
usually is the same.
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In addition to the faulty TV set, the most suspects of faulty component is about 電解電容.
few web pages found as following, they are targets to ESR meter which is homebrew, of course, if you do not mind spend U$xxx to get one of marketed ESR meter, do it.

This is also well enough description to let me know what is ESR and what is the ESR meter doing,

http://ludens.cl/Electron/esr/esr.html

http://members.shaw.ca/swstuff/esrmeter.html