Monday, February 7, 2011


This report is brought to you courtesy of Mr Beh...We at humtech electronics take this opportunity to thank him for sharing with others...hope this report will encourage others to share their experiences also.....

…and without wasting much of your time let join Mr Beh in the classroom....

I received this TV from one of my friend to repair. It is 10 years old and No diagram was found.  The problem of TV was no power with pilot lamp on and fuse was not blown.
I used voltage testing method for repair of this set:.

Entrance AC voltage to bridge rectifier (LN4SB60) was good also 320 v dc On two poles of big cap mentioned that the big cap is running well. by assistance of goggle I found out that the vcc For STR (STRS6707)   Must be 15 v DC but the voltage on the ic vcc pin9 was 7.5 v dc and This indicate that STR could be leaking the voltages 

after changing The STR with new one the TV start to work but just for few seconds.(the sound was good ). 

 I check all other parts around second part of SMPS .also big transistor (HOT) of set was not giving good answer under test by volt ohmmeter (D1787). After substitution with (D2025) TV started to work steadily.  But still no picture and only three Horizontal line on screen. This means no vertical deflection I proceed to vertical deflection ic in vertical section of the set it was hot like hell and also a big crack on the face of ic was visible this is (LA7830). 

After changing this ic TV start to work also I got the picture very clear and sharp. 

i want to mention that during the work on this TV I used isolator transformer for more safety


  1. Hi Beh, thanks for sharing to us...i admire the way you use sight, touch and voltage testing to get the culprits real fast....regards Humphrey

    the part 2 of this report will come very soon
    thanks & best regards

  3. I usually start by checking the HOT (horz output transistor) first. A bad HOT can blow out the STR voltage regulator so check it first. Always re-solder the pins on the vertical output ic and the horz driver transformer.
    On Sony tv's carefully check all solder joints because these sets often have that problem.

  4. Hi Friend, noted and thanks for your input