Is there a proper way of discharging the TV to make it safe to work on and remove the main board (not the tube board)? I can see exposed metal wires going across the tube, but the tube does not really have a metal surrounding frame that is that visible (covered with plastic case). What do I need and what is the procedure for discharging a tube, and when will I know if it's safe to remove the thick black wire going from the board to the rubber suction cup on the tube, so that I can remove the board and work on it? Thanks
First off there is no capacitor that holds the High voltage on the tube. Its the tube itself that stores the charge and if you dont discharge a tube properly it will bite you!!You can disconnect the 2nd anode of the tube(thats what the cup is called)that puppy can hold a charge for months as I've picked up used tubes that other service men may have striped out of a junk sets and still got zapped weeks later and it can burn a hole right in you if it bites you the right way. That metal strap is the ground for the crt(the picture tube) The proper way to saftly discharge a crt would be to take a screwdriver perferably a flat tip and connect a cliplead to the screw driver and clip the other end to the ground strap. Carefully slide the screwdriver up UNDER the cup on the crt till you reach the middle of the tube as you will feel it as it wont go any farther. In the meantime you might hear a pop sound and that would be the dischargeing of the tube.. Keep that screwdriver in place a min. of 30 to 40 secs. then remove . Then pinch the cup the oppisite direction on both sides that the wire is running as the cup is held in place by a small hooks on both sides Be carefull not to rip off the cup or bend the small hole suround that the cup is attached. And never ever poke a hole in the cup as I've seen peeps do and when you turn back on a set you will have fireworks as the high voltage will arch out all over the place and if your hand or face is close to it it will get you too!! Now take the clip lead and attach to the grounding strap and clip the other end to where you just took off the cup and your all set.Good Luck with your repair
Have you read my post????? WEll?? Go ahead!!
yes sir . In the past I have repaired this chassis but I dont have a schematic. Are you sure you got the right model #.. Do you see a chassis #. I reconize trhis chassis as one I repaired not long ago. You see the first picture you sent?? Theres the small end of the heat sink theres a small electrolitic cap wheres theres two bigger ones right on top. well its that smaller one then the one on the diagonal left then the next diagonal left one right above that one too. Now theres another one you gotta replace too. ite right off the flyback transformer and it will have the same c400seris or c500 seris of capacitors that the other vert caps will have . Do you understand what i mean?? Good luck and if you can please report back and let us all know how it went please. Good Luck.
Great Glad to hear this!! Ok that high pitch noise is the flyback(high voltage transformer) or the deflection yolk arund the Picture tube. The fly squeal you cant do much as I've tryed lots of things and nothing seems to last except replacement. No the deflection yolk noise or buzz can be minumized by pushing pop cycle stick up under neathe the coils but you gotta be very carefull as theres alt of voltage there. if you put on the back is it really bothersome?? s its best not to try to fool with thes devices. Ok also another coil on the PCB could be making the ringing noise also. Listening very close and tracking down its location may help you decide on where the problem lies/.. Good Luck
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Hi! First of all, If you don't have any technical training, I advise you to take it to a shop for repair, but the old way to discharge the tube is to take a long screwdriver, connect an aligator clip from the steel shaft to ground on the chassis, then making sure you hold the plastic handle of the screwdriver only, slide the end of the screwdriver under the suction cup on the tube, you will feel it hit a metal clip, and if it is still charged, there will be a loud "snap" as the tube discharges to ground. Again, I must stress this can be very dangerous, and I don't recommend you do it, but if your going to work inside the set regarless.... then this procedure should make it safer for you.
People should not be commenting on jobs like this unless they do this for a living.
The only time you need to discharge the high voltage left in the high
voltage anode on the CRT is if you need to remove the high voltage
flyback lead from the CRT. If you do, don't use a screwdriver and a
clip as most places tell you. I have seen the voltage jump over the
handle of a screw driver. If you are an amateur, then put a nail in a
piece of wood (at least two feet long). Connect an alligator clip to
the nail and the ground ******** the back of the CRT. Slide the nail
under the anode cap. Move it around to discharge as much as you can.
Make sure you only hold on to the wood. As someone mentioned, the
one-hand-rule tells you to hold one hand behind your back while you do
this just to be safe.
If you are starting to do this for a living, use your high
voltage meter to discharge most of the voltage. Then you can use the
screwdriver and alligator clip to remove whatever is left.
You are lucky that your TV was unplugged for so long and most of the voltage dissipated.
It's also a good idea to discharge the main filter capacitor in the
power supply if you need to work in the primary section. Use a 10K
resistor connected to an alligator clip which is clipped to the ground
side of the capacitor. Handle the resistor with a good pair of
insolated pliers. Do not use the chassis ground since it is for the
secondary circuit, not for the primary (assuming you have a switching
powersupply in your TV).
Congrats on repairing the fault in your TV. Well done. The ringing you
are getting may be the flyback, but is most likely caused by one of the
coils. You can tell which one it is by running the TV and using a
wooden ruler to touch each coil. When you find the right one the pitch
will change as you move the coil slightly. This MAY be solved by
replacing the coil, glueing the coil to the chassis, replacing any
capacitors connected to the coil, or in the worst case scenerio
removing the coil, soldering wires to the coil leads, mounting the coil
to whatever is handy using plastic ties and then soldering the wires
into the holes the coil went in. Make sure you insulate the coil leads
well with electrical tape or heat shrink tubing. This may sound extreme
but it is a solution provided by a manufacturer to our shop to solve a
similar problem.
Make sure you observe the polarity of the coil as you did with the
capacitors. Most coils don't have a polarity, but some (such as
linearity coils) will have a stripe down one side and a mark on the
main board. If you get this wrong, you may notice the horizontal
linearity is wrong while viewing a picture.
Hi.. what we usually did , here in Indonesia, we trying to discharged the high voltage to the ground on main PCB, and what we need is just using a cable with aligator (big enough to clip a screw driver) and flat head (-) screwdriver, but make sure to disconnect tv ac plug from wall and make sure you clip to Ground (on Main PCB)like tuner metal chasis and clip the other side of clip to screw driver metal (longer screw driver is best)and trying to touch the metal connector inside the suction cap on the tube, if its just turn off a few minutes and disconnect from ac wall unit, you'll be able to hear "crack" sound when you already touch the metal connector, and leave it for 3-4 second, and trying to touch it again 2-3 times to make sure the high voltage already discharged, and you are safe to plug out the rubber suction cup from the tube. Bonie
Leaving it unplugged for three days or even three months DEFINITELY WILL NOT DISCHARGE THE ELECTRICITY. You must discharge it to ground like the other people suggested. NEVER attempt repairs on CRTs without PROPERLY discharging the juice.
Waiting 3 days for the tube to discharge is not bad advice but I would'nt trust it...the pic tube can hold a charge for quite sometime. You don't need to disconnect the red high voltage lead to work on the chassis unless it's so short that you cannot remove the main board. Here's how to discharge the tube...carefully slip a flat screwdriver under the rubber cup until it touches the center connector. Now take a clip cord and fasten one end to the screwdriver and touch the other end to the outside black surface to the tube..if it's charged up you will get a spark..then wait a minute and touch it again. After you remove the board for repair place the tv's cover over the set to protect the tube. Don't leave it open because you might bump the neck of the tube and crack or break it.
I have a samsung projection tv model no.pcj522r
No video, getting getting tick sound...I was told that the board the capacitor sit on is bad, any idea how to discharge it being that this TV does not have the conventional picture tube
it has 3 seperate board
I am planning to work on my Magnavox TV (model 25TR12). All I have read about discharging of the high voltage is to connect one end of the alligator clip to the metal chassis. Since the modern TV have no metal chassis, what should be done?
Shinto
Funny, nobody mentioned that while you discharge the tube like techman explained, you got to hold your free hand in a fist behind your back. IF you do get a shock, it won't go through your hart..
Yeah ive been trying those procedure and it is safe connecting to the cup and then to the ground chassis and you heard a spark on it indecating that the picture tube is discharging.
Sony - kv-28wf1u - tv switched off to go to bed wednesday night. switched on thursday night - went to standby flashing mode. Switched on & off several times before it would work. Friday night switched on & off - went to stand by flashing mode. Nothing worked.Power & signal ok.
I used uninsulated wirepliers but was smart and held them with wet newspaper.I now play cello in gods choir.
Hi the proper way to work on the TV IS AFTER 3 DAYS THAT YOU UNPLUGED IT FROM THE WALL the capacitor will discharge itself you can check it by measuring the voltage on the board or just connect the legs with a long screwdriver good luck windman
SOURCE: tv tube
The best,and safest way is to use HV Probe
specified at least 40KV This is a direct link to
give you an idea of what it is you can search
for a better price on the Internet
http://www.mcminone.com/product.asp?product_id=72-6530&catalog_name=MCMProducts
SOURCE: safely disassembling a tv
The tube is the most dangerous part. It contains a vacuum and also a very large charge. The easiest way to make it safe is to unplug the end by removing the pc board attached to the back. Once removed, you will notice a large round plastic "pin" that is keyed. With a pair of pliers, squeeze the end of that part. This will break the end of the tube and allow air to enter. Do this carefully and only break the very end of this glass part (indide the plastic). You will hear the air enter the tube. This will effectively remove the charge at the same time.
Dan
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Huh?
That is not true. The tube can hold lethal charges for months and even years.
Does anybody else have a more informed and educated answer?
Techman,
Your solution is excellent and worked fine. When I did it, I heard nothing at all. The TV was unplugged for about 4 months though.
After probing with the screwdriver for several minutes (not having a clue how the clip looks and if the screwdriver was touching the clip) I felt confident to remove the suction cup with my hands.
Low and behold, the tube was discharged and I didn't get any shocks. I removed the PCB and now I am looking at replacing some capacitors.
This is my problem:
A ~2" black bar appears at the bottom of the
picture and the remaining picture on top of that is compressed
(squashed) vertically.
I was told to change the electrolytic capacitors in the vertical output section. Do you think this is the proper solution? The TV is actually a 1992 Panasonic PC-29XF10A (I wasn't able to find that model # on the site)
Have you ever experienced such a problem?
Have a look at the section in general. This is the vertical output chip (weird package) on the heatsink.
Thanks
Here's another pic from a different angle.
The chassis # is: YAPEDP218
The TV was bought in Canada, and I tried contacting Panasonic for the schematic and they said they don't carry the PC-29XF10A model anymore.
I'll change all the caps that are circled (especially the ones you mentioned outlined with a dot).
I'm not too sure about the cap in the flyback transformer section. I'll have to have a look at that when I get home tonight. Maybe I can post a pic and you can help me identify it as well.
Also, there's a couple tantalum caps around the vertical IC chip, think I should change those too while I'm at it?
Hey techman,
Those caps fixed the problem. TV works great now... except for one thing.
Is there any way to get rid of the high pitched hum/whistle that fades in and out every few seconds? It's really annoying. What is the cause of that, and what is the recommended solution?
Thanks again.
Have Panasonic model PC-29XF10A 1992 Tv All Ihave is a horizontal line accross the centre of the screen sound OK.Stan.
It is true that TVs are dangerous to work on and require a skilled engineer, but I will work on a TV (using my basic soldering skills and understanding faults) when the TV engineer refuses to repair the set.
It annoys me when they refuse purely because they believe it is too old.
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