Customer support-via email between me and a customer from Philippines

 

Good day Sir,

                   I like the book. it made my mind open in terms of CRT Tv repairing which my former lecturer in basic electronic course did not even gave us a single technique like you did. Thank you so much.

                   Sir i need your opinion regarding of the TV i am repairing,It’s a Sanyo 21",it came from my cousin.It arrived dead set.I check inside,fuse was good but the surge limiter was open so i replace it.

Wait a minute Noli, did you say the surge limiter was open, Surge limiter and fuse never open without a cause which is usually a short in the supply or components.

I test the tv with series bulb and I check the secondary output B+ found 90vdc only.Then i heard a click on crt neck and

i found a bit of  light on crt gun. I slightly adjust the screen up and i found a red horizontal line on the display.It conclude me that i have a problem on the vertical ic.

I concur with you on this conclusion Noli.

I test the Vcc pin of the vertical ic i got 19v only so trace it backward. So to have an early result, i had replace the Vertical ic and 2 caps related to that ic but when i test the tv i still got nothing. I went to secondary again which gave the 24v. but on the time i got a 24.8v and the bulb was lighted so bright then suddenly after a seconds,the bulb became lower the light so i check again the 24v but it gave me 19v.

Normally Noli when you power tv on.. at first the bulb lights very bright for a few second then go down to low light. This is because the main capacitor which is placed across the 300 volts line is not charged and therefore have low resistance and therefore the supply will see as if there is a short on the line but the moment the capacitor charges in a fraction of a second, the capacitor will have very high resistance for the voltage pass to the ground line and hence the bulb brightness become normal.

I shut off the tv to avoid the above 24v return because it may damage some parts on that line.One time,I check the voltage on pin 2 optoisolator it reads 10.5v. Whats in my mind now is,Is the 3 feedback transistor were shorted? Thats why the feedback circuit make fun to S.O.t?

No need to fear Noli, so long as you are using the series bulb as described in my book, it will take care of that.  Please note that I am not saying you put 100 watt bulb across the fuse but powering the TV using the series lamp current limiter.

But why the problem appear like a simple vertical trouble? Why the horizontal line was red? Is the CRT board  get shorted thats why the horizontal line was red.

Usually the vertical line is white but if you see a different color it means after you have solved the vertical circuit you will again find color problems with the same tv.

I need your help Sir, I,m so confused....

Never worry Noli, as you continue reading the book all these things will become crystal clear to you and soon technician near your home town will be coming to consult you…I was also there!!

Thank you in advance.....Take care,God Bless....Noli

Thank you too Noli……Humphrey

Author CRT television repair course