We have a big screen RCA TV from the 1990's that holds very high sentimental value and I'd like to fix it. All that it will need is one part, but I need help with the name of that part. The problem was that it would not power on, we'd have to push the button a few times to get it to come on and over time it eventually took more pressing on the button and then stopped.
If it's just the button (switch) that'd be nice but I have a feeling it's the "transformer" or what ever the power supply is called in the old style TV. Any help is appreciated.
Here are the specs:
Brand: RCA
Model: F35050ST
Chassis: CTC169BE2
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You might want to look to Sam's Photofacts for a repair manual if you really want to tackle it. http://www.samswebsite.com/photofacts.html
There are two power supplies in there, the lower voltage for the internal boards and a high voltage PS that puts out several thousand volts. If the TV has vacuum tubes on the boards, the lower voltage PS may also put out ~400VDC. Not something you want to work on unless you really know what you're doing.
But you could give it a try on replacing the power switch, which may not be too complicated. Unplug the set for a day or two and stay far away from the high voltage cage and the second anode connection to the side of the picture tube.Also don't probe around with any metal tools or screwdrivers in there.
If it's something more complicated than just the power switch, you will definitely want the Photofact manual. -
Okay, thank you, the set has been off for a few years and unplugged. The manual is available from Sam's Photofacts for $50 and I will get it (soon).
Is there a way to test the switch or "jump" it, I have limited knowledge of AC but a very good understanding of 12V DC (cars). I have a test light, ohm meter, and enough sense not to do anything unless instructed.
I just need direction. -
A repair manual won't do you too much good without a basic knowledge of circuits and test equipment, like an oscilloscope, transistor tester, capacitor tester, etc., unless you're very lucky.
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I would pull the back off and see if you can find the leads to the front power switch. You should be able to check the switch with an ohm meter. As long as you don't power up the set, there should be no voltages remaining in there. If the switch checks out OK, then trace the wires back from it. At that point you probably need the Sams to find how the front switch controls the set. It may be a bad circuit breaker in the PS or some other problem. Sams is pretty good for tracing down problems.
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Please be very careful when opening up a TV. There is stored charge in a TV even when it is switched OFF. It will give a nasty jolt if one is not careful. I am speaking from experience. I bought a LCD TV after that bad experience. It consumes less power too.
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Originally Posted by samijubalOriginally Posted by redwudzOriginally Posted by pchan
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Talk to some independent TV repair shops that service RCA big screens.
If this is a popular model they probably have a stockpile of used parts they can tap, similar to an auto wrecking yard.
Parts from these guys might keep you going a few years to a month.Recommends: Kiva.org - Loans that change lives.
http://www.kiva.org/about -
moviegeek71,
From what you discribed (intermittent start and now dead) is usually caused by a fast-swithching diode CR4118 in the switchmode power supply. It is located on the sercondary of the transfromer that supplies 15volts. The diode will check good but under load it will supply less than 13volts caussing no startup. Very common problem on the CTC169 chassis.
RCA part# is 164590. Also a NTE580 diode will work and found at most parts houses. -
Originally Posted by pchan
I understand sentimental value, but I'd really have to advise you not to do this. If you must, pay a pro to do it so it gets done right and you don't die trying. Modern LCDs have so many advantages over old CRT TVs that I just think it's not really worth doing. -
A very big thank you to "redwudz" and "Megahurts" for the advice, it will be a few months but I'll post when I make some progress. I had a friend help me move it into the workshop today, that was a job in itself since this thing is so large.
I appreciate everyone's words about being careful, which I will do; but, my brother-in-law is a licensed electrician with 20 years of experience and he will help me work on it. I wouldn't even try if it were dangerous and I certainly wouldn't work on it without his supervision.
Lastly, I agree that an LCD is better than a CRT and we do own several HDTV's. However, I don't care if this were a 19" black-and-white TV, I want to fix it for the expressed high sentimental value and part of the sentiment is fixing it myself. -
Originally Posted by moviegeek71
But seriously you should never attempt to open and a repair a TV yourself - 3 years unplugged or not have it done by a pro - it's easy tos crew around and break something else.
Competant TV repair techs use a special device to discharge . and even with pros sometimes accidents happen. -
"It's been unplugged for over three years, if there is something in there that can store vast amounts of energy for that long, RCA should patent and market it."
RCA no longer exists. However, it has been done. It is called a "picture tube". The CRT/picture tube of older sets stores the energy/charge very well.
Redwudz said " stay far away from the high voltage cage and the second anode connection to the side of the picture tube. exclaim.gif Also don't probe around with any metal tools or screwdrivers in there."
There is a good reason he said that. When operating, that anode can have upwards of 25,000 volts. You can turn the set off and the charge will stay there. Whenever I worked on those older sets and needed to be around that area (or replace the CRT) I would always take a BIG flat blade screwdriver with a jumper attached to it and the other end to the chassis ground and push it under the rubber cap and short out the anode lead. I would use the screwdriver to also push the clip in to remove the lead and then I would jumper that lead to chassis ground while working on the set (unplugged, of course). I could go back and jumper with that screwdriver the anode contact on that picture tube 20 minutes later and still draw a spark. That CRT is just like one big capacitor with no bleed resistor around it.
If you don't know what you are doing in there, it is best to stay away from it.
Just because a person is an electrician does not mean they are good for working on televisions. A TV is not electrical. It is electronic. They are not the same, although there are similarities.
A good public library may have the Sams Photofact series that you can go see and copy there. I know mine does. I spent many times there getting the pages I needed for different sets I worked on. -
Originally Posted by kimco52Recommends: Kiva.org - Loans that change lives.
http://www.kiva.org/about -
If it has a CRT you MUST make sure to properly discharge it. Capacitors can hold a charge for a VERY long time and a CRT can store a charge indefinitely, unless there is a bleeder-resister in the circuit somewhere. I started in electronics with 'tube' TVs. The CRT is the thing most people forget about, they grab onto the anode, the suction-cup looking thing on the tube and pull
Be careful, they WILL light you up! Kimco52 has it exactly right. -
Okay, thank you kindly, what is the name of the tool to discharge it? I will rent or buy the tool. I want to fix it myself, but I won't do anything against the advice of the experienced.
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Originally Posted by edDV
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It is a highly technical device. As I said in my post, "I would always take a BIG flat blade screwdriver with a jumper attached to it and the other end to the chassis ground".
I use one about a foot long with a 3/8" wide flat blade. I have various jumper cables on my workbench. I take one about 12-18 inch long, clip one end to the metal blade/shaft, clip the other to chassis ground as I mentioned. I might use a longer jumper and/or a shorter screwdriver. Depends on what is handy at the moment.
I use one hand and keep the other behind me or on some non conductive point or in my pocket or wherever.
But, I know what I am doing and what not to touch and do. I also plan my attach before I do it. I also understand electronics and can troubleshoot down to the component. It gets more complicated with newer stuff.
Your mileage may vary. -
Originally Posted by moviegeek71
Bare minimum, use a heavy rubber glove and a regular pair of pliers. Leave it there for a minute or two. That should fully discharge the CRT. But if it's been unplugged that long, it's likely completely dead already.Remove the resistor and touch the jumper directly to the second anode. That will assure it's completely dead.
The resistor just keeps the current flow lower.
Standard rule when working with high voltage circuits, only put one hand at a time in there. That should keep any current from flowing though vital organs. All of this is likely overkill, but working around high voltage circuits, you can't be to careful.Rubber gloves, even the thin latex type are a good idea.
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Okay, many thanks again, once I get to doing this I'll post pictures without the cover and take your advice as to what to touch and what not to touch. Thank you!
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Some of the RCA 35" sets with the CTC169 chassis have the HV anode lead sealed with a silicon compound to the CRT. Not a good idea to break the seal.
BTW: You can work on this chassis without removing the anode lead.
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