Author Topic: Water damaged CRT TV  (Read 11044 times)

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Offline Srbel

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Water damaged CRT TV
« on: August 02, 2016, 02:21:12 pm »
After taking a brake from the forum, for receiving insults, I am back. For now.

So, the water has gotten into a TV (from the top) while it was ON. It spared and since then - no picture (black screen). After like a month, I open it, water is all gone. There are marks that show where the water has been. It was not much at all.
When I turn it ON, I can hear SMPS and HV sound. There is nothing on the screen (just black, no "snow"). When I turn it off, there is a white square that shrinks into a dot in the centre of the screen, and there is a loud sound of "vacuum forming" (can not explain it better than that).

Allegedly, CRT steering coils are at fault. But I do not believe that. I measure about 2-2,5 ohms on one, and about 13 ohms on the other. I don't believe that it got to 13 ohms by water damage, I think that it got there gradually with time (TV is from 1987.).

What do you think is the problem? What are the normal resistance values for those coils?

Steering coils:



An actual TV:
https://s32.postimg.org/h3zg3ayyd/IMG_20160801_140524.jpg
https://s32.postimg.org/nmsag8b5h/IMG_20160801_140120.jpg
https://s32.postimg.org/8o9vlsw39/IMG_20160801_140332.jpg
https://s32.postimg.org/4qmlwe99x/IMG_20160801_140425.jpg
 

Offline station240

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Re: Water damaged CRT TV
« Reply #1 on: August 02, 2016, 02:46:41 pm »
Electron gun/signal problem.
That you get a white square indicates you do have proper function in the deflection coils.

So what should you do ?
Clean the muck off the PCBs for a start, that white residue can be conductive.

At a guess you have no signal getting to the PCB attached to the neck of the tube, how far back that lack of signal goes is something you need to figure out.
Try not to fry yourself.
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #2 on: August 02, 2016, 02:56:07 pm »
Thanks. Unfortunately, I can not clean it (there is a lot of dust). I mean I have no place to go to clean it. :/

P.S. Pushing the ON/OFF button a few times is not enough to discharge the CRT? Should be for capacitor, but CRT? :/
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #3 on: August 02, 2016, 03:09:41 pm »
When I try it with coils disconnected from the main board, nothing happens. I turn it on, and there is no picture, no dot, not even power supply sound. When I switch it off, also nothing (there is no longer that sound and square).
 

Offline iXod

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Re: Water damaged CRT TV
« Reply #4 on: August 02, 2016, 03:24:18 pm »
If no audio, not even static (is this an old-style broadcast TV (composite video input, etc.?)), look at SMPS output voltages, supply to ICs in audio section. I would not be focusing on the HV or steering circuits if there was no audio.

Can you input a signal to the audio inputs (from signal gen, or radio or VCR. (c; )
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #5 on: August 02, 2016, 03:35:06 pm »
I have tested it without an input signal (antenna). I was talking about PSU sound (buzzing), not sound from the speakers.
 

Offline Kilrah

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Re: Water damaged CRT TV
« Reply #6 on: August 02, 2016, 04:11:11 pm »
As a starting point you will have to clean the thing, and check all connectors for oxidation/clean it. Inclucding tube end PCB.

 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #7 on: August 02, 2016, 06:05:11 pm »
Just not possible. I live in a flat, not in a house.
 

Offline Kleinstein

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Re: Water damaged CRT TV
« Reply #8 on: August 02, 2016, 07:38:06 pm »
Repairing a CRT TV is not very useful anymore. They are just outdated and just to power hungry and usually no SAT / DVBT.
With a little luck you get used ones, still working for very little money or even free. I just send a working one to recycling as nobody wanted it, even for free.

It could be just dirt causing sparks - so if you are lucky cleaning could be enough. But these sparks could also do some damage (e.g. burn marks on board that stay conductive, damage isolation) that is hard to repair.
 

Offline Kilrah

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Re: Water damaged CRT TV
« Reply #9 on: August 02, 2016, 08:12:37 pm »
Just not possible. I live in a flat, not in a house.
You might not want to take an air compressor and blow the whole crap, but how does that prevent you from carefully scrubbing everything?

Without cleaning it will be hard to find where the dirt and water may or may not have caused unwanted current paths.
 

Offline pinyoro

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Re: Water damaged CRT TV
« Reply #10 on: August 02, 2016, 08:41:37 pm »
Take the tv outside and clean it there ????
 

Offline jjelec

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Re: Water damaged CRT TV
« Reply #11 on: August 03, 2016, 01:31:02 am »
Sound like dust and moisture on crt panel, particularly around the screen grid resistors.Or resistor itself O/C, usually around 270K.
Check voltages on crt socket. Momentarily short one of the cathodes to deck with a 1K resistor and you should get that colour very bright raster.
Cheers, JJ
 

Offline iXod

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Re: Water damaged CRT TV
« Reply #12 on: August 03, 2016, 01:59:42 am »
I have tested it without an input signal (antenna). I was talking about PSU sound (buzzing), not sound from the speakers.
It would be helpful to know if the TV will take an audio signal and play it through the speakers. Then we might know that the problem is isolated to video and HV.

If you can't clean it, if you can't plug in some audio, we're limited in how we can help you. We can't fix it for you.  ;)
 

Offline lowimpedance

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Re: Water damaged CRT TV
« Reply #13 on: August 03, 2016, 03:49:13 am »
Thanks. Unfortunately, I can not clean it (there is a lot of dust). I mean I have no place to go to clean it. :/

P.S. Pushing the ON/OFF button a few times is not enough to discharge the CRT? Should be for capacitor, but CRT? :/
A vacuum cleaner and a 1" paint brush to agitate loose the dust will take care of it with minimal disturbance.
A damp rag around the tube and then tooth brush and some IPA for the PCBs affected.
 
And remember the tube will not discharge straight away and needs to be left for some time before you get near it with the damp rag!!!. (the power switch will not make any difference to this CRT charge).

Given you get a white dot means the HV is functional. As stated before the scan drive is not getting to the deflection coils (which I would say are probably okay).
After vacuuming the dust away check for bad /corroded connectors as others have suggested etc.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #14 on: August 03, 2016, 06:01:46 am »
I will see if I can clean it a bit. :/

I don’t have any antenna output. I have an IPTV in my flat, and this TV only has classic antenna input. I don’t even have room (indoor) antenna to try it with.
« Last Edit: August 03, 2016, 06:11:16 am by Srbel »
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #15 on: August 03, 2016, 08:08:59 am »
OK, I have cleaned it. With a brush and a vacuum cleaner. But there was a lot of stuck dirt on the main board that could not be cleaned this way, so I had to disassemble the boards, and wash the main one with water in the shower. :/
So, in the next few days, until it is completely dry, no repairs...
 

Offline iXod

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Re: Water damaged CRT TV
« Reply #16 on: August 03, 2016, 05:12:59 pm »
 :clap:   :-+
 
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Offline Srbel

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Re: Water damaged CRT TV
« Reply #17 on: August 04, 2016, 02:20:30 pm »
The board is completely dry now. But there is limescale residue from the water. Do I need to clean that too?
 

Offline rsjsouza

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Re: Water damaged CRT TV
« Reply #18 on: August 04, 2016, 04:21:50 pm »
Given the high voltages present in a CRT television set, sometimes a few hundreds of ohms created by residue can create a path for current to flow. Therefore, the ideal scenario is to get the board looking like new...

I don't know how bad the residue is in the board, but where I live the residue only from the water is very minimal - on the other hand, where my parents live (close to the sea), the residue is like a short circuit (few ohms).
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Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #19 on: August 04, 2016, 06:36:33 pm »
I have used tap-water. The same water I drink.
I will see if I can clean it with alcohol and a brush. But all that brushing and also that vacuum-cleaner, I'm afraid not to kill something with static. I don't have an anti-static brush. :/
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #20 on: August 05, 2016, 09:25:33 am »
OK, I have assembled the TV. I have also found a broken trace on the main board, and repaired it.

Now, when I turn on the TV, there is still nothing on the screen (no antenna, so it should show "snow"/static).
But, the difference from before is that now the LED screen (that shows what TV channel is selected) works, and when I change the channels it shows that. Also, when I turn off the TV, now there is no white square that shrinks into a dot, and there is no loud sound of vacuum. Now it sounds normally when turned off. Remote control works.

But the screen is actually OFF. It remains completely the same whether the TV in on or off. :/

Also, there is some cracking heard from the speaker.
« Last Edit: August 05, 2016, 09:31:22 am by Srbel »
 

Offline OE2WHP

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Re: Water damaged CRT TV
« Reply #21 on: August 05, 2016, 11:55:38 am »

Never ever wash a pcb in the shower. Tap water isn't just H2O. Even if you dry it afterwards, there will remain residues on the board and most probably also in some parts.
 Next, there could be parts on the pcb which must not be submerged because it will cause dammage inside the part. Then there are parts where the water will get in but you won't ever get the water back out.

For me it sounds like you have no clue what you are doing.
Said that, I highly recommend, don't play around with high voltage devices! Involve someone who has the knowledge or just buy a new tv set.
 
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Offline Srbel

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Re: Water damaged CRT TV
« Reply #22 on: August 05, 2016, 12:27:15 pm »

Never ever wash a pcb in the shower. Tap water isn't just H2O. Even if you dry it afterwards, there will remain residues on the board and most probably also in some parts.
 Next, there could be parts on the pcb which must not be submerged because it will cause dammage inside the part. Then there are parts where the water will get in but you won't ever get the water back out.

For me it sounds like you have no clue what you are doing.
Said that, I highly recommend, don't play around with high voltage devices! Involve someone who has the knowledge or just buy a new tv set.

Stop pretending you are smart, and that I am clueless. It is easy to do that over the internet, but in person you would not be able to do that to me and just walk away. If you have nothing helpful to say, leave.
This is the kind of people that made me leave this forum for months.
 

Offline OE2WHP

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Re: Water damaged CRT TV
« Reply #23 on: August 05, 2016, 12:48:49 pm »
Sorry mate,

not just pretending. I worked as a professional radio & television technician for 15 years. After that i made a degree in electronics engineering.
I pretty well know what I'm talking about.

Cleaning a tv means, take a vac a brush und eventually some alcohol but never ever use tap water to rinse or submerge the board.

You also seem to have no idea if and how long a tube holds its hv and how to safely discharge it PRIOR to any work on the tv set.

The resistance of H & V deflection coils are different of course. 

All that are fundamental basics.

And no, i didn't say you are dumb, you just don't know how to work on tv sets and that can be dangerous and in most of the cases it does not lead back to a working tv.

By the way, if we would have had this discussion face to face I would have given you the same advice.

Sorry, if sounding rude. I'm not a native speaker.

73


« Last Edit: September 06, 2016, 08:16:51 am by OE2WHP »
 
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Offline Srbel

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Re: Water damaged CRT TV
« Reply #24 on: August 05, 2016, 01:47:25 pm »
I am not going to read your BS. Go harass someone else.  You are not smarter than me. You know nothing about me. Go away. You are not helping.
 


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