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Old 23rd Aug 2021, 1:24 pm   #1
Miguel Lopez
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Default Problem with a second TV set

Hello everybody

On recent times I posted a problem with my SANYO TVS1430MA. I solved the problem by resoldering many dry joints on the PCB.

Now our second TV set is giving me some problems too. This time it is a Chinese Panda PCB and CRT, inside a Sony Trinitron cabinet. This kind of Frankensteins are common in Cuba.

This TV set starts with the picture blurred (photos 4 and 5) and then jumps to a picture reduced to a narrow horizontal band in the middle of the screen, and the picture is upside down and seems to be rolled in the upper border (photos 1,2 and 3). After a couple of minutes the pictures appears OK in the screen and does not fail again for all the time that the TV set is working.

I know nothing about TV sets, so I'm asking for help on where to look for this flaw. Surely a faulty component, but I don't know how to identify it. I have given a look to the PCB and found no dry joints and no inflated capacitors so I don't know where to look for the problem

Any help regarding this will much apretiated. I have opened this thread here as this TV set is 10 years old and refurbished. Not sure if this already classifies as vintage. Mods should tell.

See the attached pictures for more details

Thanks in advance
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Old 23rd Aug 2021, 1:50 pm   #2
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Default Re: Problem with a second TV set

I would look for dried out capacitors in the frame output stage. They are often close to the frame output heat sink and dry out quickly.
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Old 23rd Aug 2021, 2:54 pm   #3
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Default Re: Problem with a second TV set

Yes indeed. Electrolytics in the frame stage. Replace all and also the ones in the line stage for reliability.
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Old 23rd Aug 2021, 3:08 pm   #4
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Default Re: Problem with a second TV set

Just to increase my knowledge. What would be the frame stage? I'm a pagan on TV sets

I took pictures of the PCB but I left them at home. I will share them tomorrow. The PCB is separated by sections with drawn white lines, and identificated with the function of avery section, but to be honest I don't remember if they are in Spanish or English. Tomorrow I will share them and you could help me where to replace the caps. I can replace them with higher voltage capacitors if needed.
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Old 23rd Aug 2021, 3:45 pm   #5
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Default Re: Problem with a second TV set

Hello again Miguel it's been a while, I am too a TV pagen (I like the use of pagen) at least the set works to some extent, should be simple. I now bow out to the TV experts here.
 
Old 23rd Aug 2021, 4:02 pm   #6
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Default Re: Problem with a second TV set

If you trace the wires from the scan yoke; 2 will go to the line stage and the other 2 will go to the frame driver stage, likely to be an IC in this set. Most such ICs were vertical SIP type packages mounted on a heat sink. Replace all the electrolytics in this area.

Do you have a schematic?
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Old 23rd Aug 2021, 5:12 pm   #7
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Default Re: Problem with a second TV set

Quote:
Originally Posted by agardiner View Post
Do you have a schematic?
I've got the whole documentation of this set. It was very spreaded in Cuba about 20 years ago
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Old 23rd Aug 2021, 5:25 pm   #8
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Default Re: Problem with a second TV set

So, N401 is the frame driver.

Start by replacing C406, C414, C408, C404 & C405.
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Old 23rd Aug 2021, 7:06 pm   #9
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Default Re: Problem with a second TV set

I will be replacing those caps on weekend. Power cuts are frequent now and I don't want to have a power cut with the TV set disassembled with parts sitting around.

I will let you know the results. Thank you very much to all of you.
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Old 24th Aug 2021, 2:58 pm   #10
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Default Re: Problem with a second TV set

Here some pictures of the TV inside. Not the best pictures but it's what I've got right now. I will take better pictures when I replace the caps.

Picture #3 should be the vertical amplifier
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Old 30th Aug 2021, 1:25 pm   #11
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Default Re: Problem with a second TV set

Hi all

I couldn't do the repair on weekend, due to Hurricane Ida mostly. We were without electricity since 3:00 o'clock on Friday till 3:00 o'clock on Saturday. It was due to a fault on the electric system, as the rest of the town had power. It should had been a fallen tree or pole.

Then I focussed on my DC Back Up system building a 12V DC fan to be powered by my battery, in the case of another black out that night. It is impossible to sleep without the air conditioner or a fan, due to heat.

Saddly I can not repair the TV set on week days as I return from the job at 6:00 o'clock and there is the risk of a power cut at that time, and I don't want to have the TV set disarmed on the table in the case of a power cut, not knowing when power will be restored. I must wait until next Saturday. The TV set keep doing the same fault. (of course, it will not get repaired by itself , I mean it has not worsened so far)
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Last edited by Miguel Lopez; 30th Aug 2021 at 1:43 pm.
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Old 7th Sep 2021, 12:29 pm   #12
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Default Re: Problem with a second TV set

Hello

This weekend I had the time to give a try to the TV. I replaced all of the electrolytic capacitors in the vertical section, and the problem got worse. Now the TV set only has a horizontal bright line in the middle of the screen. All of the capacitors that I mounted were checked for capacitance and reformed before use them. I re-mounted the original capacitors and the problem remains unaltered (see the pictures)
I decided not to go on with this adventure and ask for the assistance of the guy who fixes the TV sets in the town. Saddly, he is recovering from Covid-19 right now, so I have to wait for a while. I will let you know when the TV is fixed. Thanks a lot to everyone.
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Old 7th Sep 2021, 1:42 pm   #13
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Default Re: Problem with a second TV set

There is no vertical deflection. The IC itself might be bad, its feed resistor open, a diode/cap in its supply line from the line o/p transformer is bad, or maybe the connections to the yoke came loose when you were moving the board. Let's hope you get it solved, let us know how it goes.

Falta la deflexión vertical. Puede que el integrado esté mal, o su resistencia de protección esté abierta. A veces, el diodo y/o el condensador que filtran el voltage derivado del trafo. de lineas se estropeen. Tampoco hay que descartar lo mas sencillo; al mover la placa, puede que se haya soltado un cablecito que va al yugo. A ver si hay suerte, ya nos comentarás!
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Old 27th Sep 2021, 6:28 pm   #14
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Default Re: Problem with a second TV set

Hi, the TV set is already fixed. I took it to the local mechanic and the guy fixed it in a while. It was the vertical deflection chip which was kaput. He also found a faulty 7805 regulator. Both components were replaced and the TV set is OK right now.

Today I will bring the other TV set (the Sanyo) to him to solve the "misterious case of the missing green"

I decided (learnt by the hard way) that fixing TV sets is not my strenght, so I better take the TVs to the one who knows. He also need to eat, don't you think?
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Old 27th Sep 2021, 6:44 pm   #15
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Great result! ¡Un final feliz!
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Old 28th Sep 2021, 9:59 am   #16
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Default Re: Problem with a second TV set

Well done, but you have learned from this experience.

I always used to think that CRT TVs needed a "specialist" to fix, but I've mended dozens over the years, learning from books, magazines, and just playing around with old sets.

Many faults are trivial (dry joints, cracked print) and many others can be fixed with a circuit diagram, multimeter and if all else fails, a bit of component substitution. And many sets had "stock faults", in other words, a particular model had a particular weak spot which made fault-finding even easier.

Over here, in the late 1980s and 1990s, I could find a colour TV thrown out in the street very easily, take it home, get the circuit diagram from the local library, and mend it in my student bedroom with just a soldering iron, ancient multimeter and some bits salvaged from other old TVs. If I needed any new parts, there were plenty of small independent dealers I could order from by phone or fax, with the parts arriving by post a day later.

20 years later, most "street TVs" which I found were in perfect working order. A bonus in many respects, but no more fun!

Last edited by Nickthedentist; 28th Sep 2021 at 10:06 am.
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