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TV repair HELP needed.

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vlad777

Member
The tv picture is all red and
theres about 12 lines that are
almoast horisontale.
(Which could make me think that
horisontal frequency is few times (12)
higher than normal)

Brightnes pot has no effect on the picture.

The vodeo-chroma-deflection system
is all controled by big chip TA7698AP
Which I tried to change(with CD7698)
but get the same result.

The TV is: Samsung CB-528ZSE


Any help is highly apreciated.
Thanks.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Check the cathode voltages on the CRT base - randomly changing IC's on the main board is no way to try and repair anything. Most likely the fault is on the CRT base, or the CRT is duff.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
RK-0V ~
GK-130V ~
BK-254V ~

I dont have osciloscope , those are results taken by multimer.
But how do you explane horisontal lines?
They are flyback lines - normally blanked out during flyback, but the fault prevents that happening.

Assuming it uses separate output transistors?, remove the red one - if the picture is still red, the CRT is duff.
 
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vlad777

Member
Flyback lines . Thanks I get it.
I tryed removing all three transistors - same result.

Whith only green tansistor starts blue whith
picture(video) bellow the lines than after few seconds
becomes red-orange and the picture can
be barely seen.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Yes, sounds like it's not the CRT.

Assuming the transistors are all OK?, check for high value resistors on the tube base. Often 180K or so, and they commonly go high.
 

MAGNETRON

New Member
Check the red output transistor Collector/emitter Short circuit,also with the transistors out,put say the green output transistor in the red output position,switch on,do you get a normal red picture?ie no flyback lines,if so change the original red output transistor,
output transistors are common for going faulty:)
 

vlad777

Member
I took off all electronic from the tube.
I connected red cathode pin to one wire.
I connected heater two pins in short circuit
to another wire and applyed high voltage.
I hoped since three filaments are suppose to be in paralel
that this would burn only the red one (or just the contact).
Instead all filaments DIED.

So that's it.
 

HiTech

Well-Known Member
So, I guess you are telling us that you fixed it for good? Right?

If you applied high voltage to the filaments, you certainly fried them and the CRT is caputz! Sounds like your curiosity killed the cat. Your satisfaction won't bring it back! Have a funeral for the television set and invite us to just the wake afterwards.
 
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MAGNETRON

New Member
When trying to get 'Crud' as I used to call it off the cathode,I would disconnect the crt base(all electronics well away from tube)ground the offending cathode,and then apply a high voltage quickly to the first grid in the tube,this attracts the 'crud' off the cathode(or any 'crud' that is intermittently shorting between electrodes),worked many a time as a last resort,never stuck high voltages on the heater/filament side,asking for trouble there!
 

Nigel Goodwin

Super Moderator
Most Helpful Member
When trying to get 'Crud' as I used to call it off the cathode,I would disconnect the crt base(all electronics well away from tube)ground the offending cathode,and then apply a high voltage quickly to the first grid in the tube,this attracts the 'crud' off the cathode(or any 'crud' that is intermittently shorting between electrodes),worked many a time as a last resort,never stuck high voltages on the heater/filament side,asking for trouble there!
I've never done it (never seemed any point), but the classic method was to apply a charged capacitor to the heater and affending cathode (with the CRT base unplugged) - the 'blast' from the capacitor blows the short off.
 

HiTech

Well-Known Member
I believe that's basically basically what CRT rejuvenators do since you can measure the decaying voltage being applied. The rejuvenator simply adds a measurement circuit to test for shorts and emissions.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Not to 'rejuvenate' they don't - to rejuvenate you apply double the normal heater voltage, and pass a fairly high current though the cathode/screen grid - this blows deposits off the cathode.

You then have the option (if needed - almost always is) of pressing a button and removing the shorts caused by the bits blown off the cathode.

It's this button that discharges a capacitor and removes the short (usually).
 

killivolt

Well-Known Member
Zenith's

There in the end at the shop, during Zeniths demise we were always heating up the guns on them.

I think I would clean about 2 out of 10. The rest were so bad, it wasn't even worth the time.

Edit: But, I always like pressing the buttons and watching the crud pop inside. I still don't miss lifting sony CRT's back and forth.
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
There in the end at the shop, during Zeniths demise we were always heating up the guns on them.

I think I would clean about 2 out of 10. The rest were so bad, it wasn't even worth the time.

Edit: But, I always like pressing the buttons and watching the crud pop inside. I still don't miss lifting sony CRT's back and forth.
Sony tubes never boosted very well, but neither did any in-line tubes, it was the old delta tubes where boosting worked fairly well. I've still got a B&K booster, can't remember when I last used it - apart from last century sometime :D
 

killivolt

Well-Known Member
Seems like yesterday I had my head pasted against a Black & White that was about 16" but was probably more like 12".:p

Edit: It had the gradual slope from the corners of the face down to the tube.
 
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