Friday, February 17, 2012

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


Good day Sir, I want to consult to you what I’ve learn in your book and I want you to comment and add some idea. Because I want to make a troubleshooting guide line list to make my trouble shooting fast.


1. DEAD SET TV- In order to fire up the TV set, first I check is the PSU, B+ to fly back, horizontal section and fly back transformer, jungle IC. Please comment.

First any voltage on the secondary side, especially the B+ line? If there is low voltage on the B+, then solder out the middle leg of the H.O.T transistor and apply power briefly, does the TV fire now...if yes then the problem is on the secondary side…Check if the Hot is shorted or the fly back and the surrounding components.

If no voltage on the secondary (Zero) on all the lines then concentrate on the primary power supply.

Chap 4 of your book has the detailed lists on how to go about this exercise Bogie.

2.TV WITH COLOR PROBLEM- 1st I check the voltage of cathode pins of R,G,B, at CRT board, voltage on transistor or IC which driving the R,G,B, color and components related to it. My question is, is vertical IC also have a concern with regards to color problem?

In electronics Bogie, there is no guess work…only facts…Vertical ic is used to open the screen upwards and has nothing to do with the color. Again I say stick to the method I have used in your book...Usually color problems are the easiest to solve.

3. What is your 1st move when you see a TV that has almost faded image display on white and a bit of green color?
This problem can be categorized as color problem.

Sure

4. How will I know if the CRT itself is the problem? What are the clues you will find in the display?

Take a 10K by 3 Watts resistor and solder a wire with clip on both end of the resistor, now with the TV on clip one end of this resistor to the Cold ground of the TV and the other pin on the Red Cathode-expect the screen to be all red now, move this again to Green Cathode the screen should turn Green, and last take it to the Blue cathode and the screen should turn Blue. If you do this and the entire three cathodes has the same brightness then consider the CRT tube is good.


5. JUNGLE IC- In order to function the jungle IC, it must have a 5v supply on it VCC pin. If the voltage beyond tolerance, trace backward. If found all components were good, try lifting up the jungle VCC pin. If the 5v appear, does it mean that the jungle IC is bad? Are there any indication/symptoms/clues just to know that the jungle is bad?

Usually Jungle ic use 9 volts supply, for 5 volts it usually used in Microprocessor. If 5 volts is low and the micro is getting hot then you can lift up the supply line and if this voltage goes up, then consider the micro is shorted.  If the 5 volts is high then check if the 5 volts regulator is faulty.


Thank you so much for your reply Sir I have learn a lot mostly about teaching me on how to recognize the bad or good CRT. Because sons like me badly need guidance of a good father like you. I love Electronics, it is challenging but sometimes the challenge resulting to a bit of frustration but still quitter never wins...right.

Absolutely right. Bogie

The reason I emailed you because i have a Sony model no.KV-HF21N80 which I had mention to you which have has faded picture display with horrifying color. This TV is mine for 5 years. The TV led blinking 5 times in every 30 seconds. Searching the Sony blinking codes on internet I found this site http://www.techlore.com/article/15444/Understanding-Sony-Television-Blinking-Codes/.

The TV’s cathode pins had a 112v +/- to all RGB cathode pins which suppose to be 150v likewise on RGB transistor C-110v+/- B-8.82 & E-8.30.On base and emitter was confused me so I replace them all but still I got the same reading of voltages....Thank you very much. Bogie

Hi Bogie,
I don't think the tube has a problem here....
Humphrey



Good day Sir, finally I solve the problem of my TV Sony KV-HF21N80 by replacing the IC1751.

The symptom was washed out color and almost faded picture display. As I’ve applied measuring voltages on all RGB cathode pins found 112v +/-, 3-RGB transistors collector (110v +/-), Base (8.30v +/-) and Emitter (8.30v +/-) and replacing them did not cure the TV.

I almost test all the components at CRT board but nothing found any bad one. And even the 3 transistors which I had replaced were good too. TV has 5 blink code which is the code says "Problem in IK drive circuit". After research of this IK drive circuit finally found the solution. Attach here is the training manual of SONY KVxxxxx model where I found the idea

It’s a nice piece which wake me up in the idea of not all color problem were not only be found by troubleshooting the CRT Board

It’s really nice to know the technology of each brand what was the manufacturer did their design on each of their release model of TV. GOD BLESS US ALL....Bogie of Philippines




After reading my last email from Bogie, I particularly became interested with the last bit underlined above where he said that… It’s a nice piece which wake me up in the idea of not all color problem were not only be found by troubleshooting the CRT Board

So I searched on the training manual he send me for this I.C 1751 and this is what I got.



From the circuit above you can clearly see that this ic1751 is actually the RGB driver IC.


The RGB signals from the A-Board are first amplified by transistors Q761, Q771 and Q781 then pass through two transistor buffer banks (Q762; Q772; Q782 and Q763; Q773; Q783) on the CV board The amplified and buffered RGB signal is then applied to the RGB Driver IC1751/pins 1, 2 and 3. The CRT receives RGB final drive signals from outputs at IC1751/pins 7, 8 and 9.

2 comments:

  1. Well said my friend Kimathi it goes back to what you have been saying all along.....read carefully and try as much to understand the localized area of the problem which in this case was The Color Section beginning with the CRT board and write them down and as per your book that problem would have been solved even earlier it is as simple as that. My teacher Kimathi one love and God bless.

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  2. Hi Joe, Thanks for passing by Joe, and thanks for your comments. God bless you too.

    Regards Humphrey

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