Author Topic: Water damaged CRT TV  (Read 11045 times)

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Offline MosherIV

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Re: Water damaged CRT TV
« Reply #25 on: August 05, 2016, 02:13:34 pm »
Hi

Quote
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.
I both agree and disagree :
I have heard of some manufactures recommending boards be washed with water (yes normal tap water), these were ink jet printer manufacturers. As you can imagine, if a ink cartridge leaked it would leave a horrible mess on the PCBs.
I agree that washing a PCB which has high tension (another term for Very High Voltages) is probably not a good idea since lime scale residue could be a break down path.  :-\

Quote
I am not going to read your BS. Go harass someone else.
Please do not take comment so personally.
When ever you post to a public forum, you are going to get some people who will say nasty things. It is a sad  :( matter of fact.
There are many people here all very friendly and trying to help.  ;)
There are some that do not mean to be unfriendly but unfortunately the nature of their personality means they say things which they do not mean to be offensive but come out that way. Many engineers are socially awkward and say things matter of factually no matter how offensive it may sound to others. None of it is meant to be offensive or personal.

It sounds like there is some progress with your repair.
When you turn on the TV, can you feel static build up on the front of the CRT ? (indication of HT on the screen - cathode to annode electron acceleration)

(I do not remember from the first post) Did the water damage happen when the TV was turned on (this may have damaged components) ?

 

Online LazyJack

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Re: Water damaged CRT TV
« Reply #26 on: August 05, 2016, 02:19:44 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.

That is absolutely not true. For example: http://assets.fluke.com/manuals/8842a___imeng0300.pdf
Quote section 6-77.

6-77.   Cleaning Printed Circuit Assemblies
If conditions warrant, individual printed circuit assemblies (PCAs) can be cleaned with
water-based commercial cleaning systems such as dishwashers. If such systems are used,
observe the following precautions:
1. Remove all shield covers (applies to the True RMS AC PCA) and socketed ICs.
2. Use Reagent Grade 2 or better water (de-ionized or distilled water) for the final rinse
in geographic areas with exceptionally hard water.  During the final rinse, spray or
run the water so that the surface is thoroughly covered to remove all ionized material.
3. Thoroughly dry all PCAs using one of the following methods:
a. Preferably, the PCA should be dried in a low-temperature drying chamber or
infrared drying rack with a temperature range of 49°C to 72°C (120°F to 160°F).
b. If neither a drying chamber nor a drying rack is available, air dry the PCA at
ambient room temperature for at least two days.
A satisfactory cleaning method consists of holding the PCAs under hot running water
until they are clean. Follow this wash with a final rinse. (See consideration 2, above.)


I'm pretty sure Fluke knows how to handle a precision instrument. I have read similar directions in Tek and HP service manuals too.
There are components, that should not be washed, for example in many Tek scopes the attenutator assembly has "Do not was in water" warning. But such a consumer electronic stuff, like a tv could be washed with no problem whatsoever. Of course, you have to dry it properly.

 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #27 on: August 05, 2016, 02:20:56 pm »
The water got in while TV was on, yes. Something sparked inside, and then it was unplugged. After a few weeks, I took it to try to repair it.

There is some static I can feel on the front of the CRT when it is on. I placed a palm of my hand so the back of it touches (nearly touches) the glass, and I can feel static on the hairs.
« Last Edit: August 05, 2016, 02:28:18 pm by Srbel »
 

Offline stj

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Re: Water damaged CRT TV
« Reply #28 on: August 05, 2016, 02:21:36 pm »
no oldschool monitor engineers here i see! (other than me)
what make / model is it?

all crt system repair is similar.

first you test the psu, by isolating it from the high-voltage and loading it.
you need to find the B+ line from the psu to the line-output transformer.
it usually has a 100-200v electrolytic across it and an inductor afterwards.

you lift the inductor if it's *after* the electrolytic so the cap is still in the circuit.
then solder a couple of wires across the cap and connect them to a 60w 240v lamp bulb - a normal one - NOT halogen or ccfl etc.

when you turn the tv on, the lamp should light and stay on with a stable brightness.
and you can meter the voltage across it - it is sometimes ajustable.
be warned - it's going to be 80-160v dc
 
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Offline Srbel

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Re: Water damaged CRT TV
« Reply #29 on: August 05, 2016, 02:25:38 pm »
It is 1987. Philips 20CT6350.
 

Offline OE2WHP

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Re: Water damaged CRT TV
« Reply #30 on: August 05, 2016, 02:30:22 pm »

2. Use Reagent Grade 2 or better water (de-ionized or distilled water) for the final rinse
in geographic areas with exceptionally hard water.  During the final rinse, spray or
run the water so that the surface is thoroughly covered to remove all ionized material.

Sure its common practice to clean pcbs with water based cleaning systems but of course, these DO NOT use tap water.
 

Offline MosherIV

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Re: Water damaged CRT TV
« Reply #31 on: August 05, 2016, 02:42:16 pm »
Quote
Sure its common practice to clean pcbs with water based cleaning systems but of course, these DO NOT use tap water.
Sorry, have to disagree. Depends on the application of the PCB.
For TV or anything that have high voltage - yes definitely.

Quote
I worked as a professional radio & television technician for 15 years. After that i made a degree in electronics engineering.
So, yes from your background, it is standard to NOT clean PCBs in water.
(FYI I am a Chartered Engineer (CEng) with a BEng in Electrical and Electronic Engineers - so please do not tell me I do not know)

Long ago, before I went to read for my degree, I spend my summer working for an electronics service company. I worked on servicing Electronic Cash Points. They had an industrial machine cleaner - just like a giant dish washer with a flip top lid. We would put the cash point shells, including the LED displays into this machine. Had to wait for 24h for them to dry but no problems after that. They were CHEAP, so I would guess that they did NOT use deionised water!
 

Offline stj

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Re: Water damaged CRT TV
« Reply #32 on: August 05, 2016, 02:42:45 pm »
It is 1987. Philips 20CT6350.

chassis is CTO-S OR CTO-N

what number is after "20CT6350/" ?

 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #33 on: August 05, 2016, 02:45:04 pm »
It is /50R
 

Offline stj

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Re: Water damaged CRT TV
« Reply #34 on: August 05, 2016, 02:50:06 pm »
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #35 on: August 05, 2016, 02:52:28 pm »
It seems that after assembliing it back, I have connected one of the cable to the wrong connector. But I don't know which one!

There is this connector on the main board, next to the HV transformer, that is empty. But there are no loose cables.

(left from the HV transformer, under the blue electrolytic caps):
https://s32.postimg.org/mu3rl4vph/IMG_20160805_164156.jpg

I am looking at the original pictures from the first post, but I can not see what should go where.
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #36 on: August 05, 2016, 02:53:38 pm »
so it's the "CTO-S" chassis.
http://elektrotanya.com/philips_chassis_cto-s.pdf/download.html

I have an original schematics. It came with the TV.
 

Offline OE2WHP

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Re: Water damaged CRT TV
« Reply #37 on: August 05, 2016, 02:59:51 pm »
I'm not saying you dont know, also I don't intend to argue. These "Dishwashers" are quite common in electronics industry but normally they have some kind of "de-ionising" device built in or attached to it and do monitor the conductance of the water. The system rinses the pcbs until conductance is below a predefined level. These machines still look like regular dishwashers.
Maybe this is different in areas where the water hardness is already below this limit without de-ionizing but at least in europe this is not the case.

Would you agree, that tap water contains different salts which can lead to corrosion? So in general its better to avoid cleaning pcbs with tap water without rinsing with deionized water at the end?

Again, I do not intend to be rude. Please blame it to my disability to find proper words in english.

73
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #38 on: August 05, 2016, 03:00:05 pm »
OK, I think that connector is for power to the PCB that goes on the back of the CRT. By accident, I have connected that cable to one of the boards in the socket on the left, so CRT board did not get any power. Now it should. But, I don't know what is the empty connector on that daughter board for. Connector is dirty on the inside, so nothing was plugged in from the beginning.
« Last Edit: August 05, 2016, 03:02:43 pm by Srbel »
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #39 on: August 05, 2016, 03:09:41 pm »
OK, I have "snow"/static on the screen now. It seems to behave normally. I just have to get it back to the original location, and try it out with an antenna. But I think it is fixed now.
 

Offline MosherIV

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Re: Water damaged CRT TV
« Reply #40 on: August 05, 2016, 03:20:23 pm »
Quote
These "Dishwashers" are quite common in electronics industry but normally they have some kind of "de-ionising" device built in or attached to it and do monitor the conductance of the water. The system rinses the pcbs until conductance is below a predefined level.

Maybe this is different in areas where the water hardness is already below this limit without de-ionizing but at least in europe this is not the case.
That company was so cheap and skimped on everything, they even made us re-form springs instead of using new springs  :palm:
I was very young back then and I did not know about such things as the machine washer. I did not notice anything to measure the water. I do remember the big cut off value plumbed into what looked like the regular tap water supply, though it was only used to top up the machine.

Quote
Would you agree, that tap water contains different salts which can lead to corrosion?
Yes, absolutely.
I do not know what long term effects these residues have on electronics.
I know certain sectors do recommend washing in normal tap water (ie the printer manufacturers). They are not worried about longevity  >:(

Quote
So in general its better to avoid cleaning pcbs with tap water without rinsing with deionized water at the end?
I guess, if you want to have the thing still working in 30 years plus - yes a good idea.

Quote
Again, I do not intend to be rude. Please blame it to my disability to find proper words in english.
No worries. Like I said, I guessed from your background that it is a no no to wash in tap water.
The company I work at now definitely does not wash in tap water, I think they use cleaners and solvents.
Your English is pretty good. Better than my German/Austrian.  :-+
 

Offline MosherIV

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Re: Water damaged CRT TV
« Reply #41 on: August 05, 2016, 03:21:54 pm »
Quote
OK, I have "snow"/static on the screen now. It seems to behave normally. I just have to get it back to the original location, and try it out with an antenna. But I think it is fixed now.

 :-+
 8)
 
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Online LazyJack

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Re: Water damaged CRT TV
« Reply #42 on: August 05, 2016, 03:31:29 pm »

2. Use Reagent Grade 2 or better water (de-ionized or distilled water) for the final rinse
in geographic areas with exceptionally hard water.  During the final rinse, spray or
run the water so that the surface is thoroughly covered to remove all ionized material.

Sure its common practice to clean pcbs with water based cleaning systems but of course, these DO NOT use tap water.

Have you even read what it writes? It suggests using deinonized water for *final rinse* and only in areas where normal tap water it exceptionally hard.
Of course it does not hurt to use deinonized water, but for sure you won't have any problem on a TV set. Especially if you blow most of the water off. You will have very little deposit. If you want to be really celan, follow up with a rinse with IPA, it'll take the water with it.

I have cleaned numerous PCBs and whole instruments in normal TAP water, they are still fine.
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #43 on: August 05, 2016, 03:38:14 pm »
Hmm, after about 30 seconds from turning on, screen goes from white static to purple. Needs degaussing, or?
« Last Edit: August 05, 2016, 04:00:01 pm by Srbel »
 

Offline stj

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Re: Water damaged CRT TV
« Reply #44 on: August 05, 2016, 05:54:53 pm »
your losing green - trace the green signal from the tube base - could be a bad solder joint.
 
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Offline Srbel

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Re: Water damaged CRT TV
« Reply #45 on: August 06, 2016, 07:34:48 am »
This is how it looks now. Goes straight to the purple now, and the picture of static is not "stable":

http://www.megafileupload.com/7ik4/VID_20160806_090717.3gp.7z

Also, I hear crackling sound from the base of the CRT.

I will try to find cold solder joints, but I don't see any on the PCB that goes on the back of the CRT.
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #46 on: August 07, 2016, 09:42:56 am »
I have traced G line (for green colour) and there are no cold solder joints. I have also re-soldered some critical joints.

I have measured voltages at the output (for R, G and B) of the "Chrominance + Luminance - PAL" board (that sends signals to the PCB on the back of the CRT). It says in the schematics that those voltages should be 5V. I have measured 4,4V when the CRT board is disconnected from this board, and 2,45V when it is connected. It is the same for all 3 outputs (R, G and B). The IC is TDA3561A.

Also, now the CRT does not work at all again. I don't know why. :(

Edit: I have measured those voltages at DC, but now I see in datasheet that it says that those are p-p values. -.-
Edit 2: Measured on AC, I get about 300mV, so it is not a valid measurement (multimeter can only measure AC at 400 Hz max, I think)
« Last Edit: August 07, 2016, 12:07:27 pm by Srbel »
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #47 on: August 07, 2016, 12:11:09 pm »
When I disconnect the RGB signals from the PCB at the back of the CRT, CRT works. I get static. It has horizontal lines which move left-right fast. The colour is between white and blue.

It looks different colour on the photograph, plus ignore 3 big diagonal lines (those are from the camera):



Does this mean that RGB (so called: "Chrominance + Luminance - PAL" board) is faulty?
 

Offline stj

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Re: Water damaged CRT TV
« Reply #48 on: August 07, 2016, 12:32:44 pm »
what happens if you feed it an RGB signal on the scart input?

and how about any OSD text?
 

Offline Srbel

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Re: Water damaged CRT TV
« Reply #49 on: August 07, 2016, 01:01:28 pm »
There is no SCART input. just a classic antenna coaxial input (I don't know how it is called).

Oh, and with "Chrominance + Luminance - PAL" board RGB output connected to the CRT PCB (the PCB that goes on the neck of the CRT), the CRT is just black. It does not even turn on it seems.

I am not feeding any outside signals, just disconnecting and connecting signal cable from the internal boards.
« Last Edit: August 07, 2016, 01:05:30 pm by Srbel »
 


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