Can I work inside my TV without killing myself?

March 15, 2007 11:48 AM

I have a ten-year-old Sony TV that's on the fritz. It's a good enough second set that I'd like to save it if possible, but it's also big enough that it's going to be a pain to haul in to the shop for an estimate. If I decide to pop the case and dive inside for a quick sanity check, what do I need to do to avoid electrocuting myself in the process?

A couple of weeks ago the picture started rolling back up on itself -- and eventually disappearing -- a few minutes after the set was turned on. In its early stages the problem would clear up for a few minutes after a gentle thump on the side of the case, which makes me wonder if the problem is just something coming loose inside.

I'd like to try the same first-cut debug approach I'd use on a PC: opening the thing up and making sure all the wiring is connected and any PCBs/etc. are properly seated. (I have no intention of doing anything more than that.) But I know there are some fairly juicy capacitors in there that pose an electrocution hazard even if the set has been unplugged. Short of not opening the case at all, what can I do to minimize the risks of navigating the set's innards?

posted by Lazlo to technology (16 answers total)

Please don't do this; it's really quite dangerous.

I think you'll be surprised how cheap a professional repair is. I got an old Samsung CRT TV with a similar problem fixed a couple of weeks ago for $75.
posted by mr_roboto at 12:05 PM on March 15, 2007

Google for "flyback transformer." There's enough to kill you, even when it's unplugged. Its easy to discharge but you need to know how.

Unless you know what you're doing, TVs and monitors usually aren't worth working on. It's not like a computer where you can just swap out one generic component for another.
posted by bondcliff at 12:09 PM on March 15, 2007

If hitting it fixes the problem, then i believe its the tube dying. At least thats what happened to my old toshiba. The repair guy told me I could tap it with the back of a screwdriver when it does this, but it will eventually die. If you have the same problem I have then theres nothing servicable in there. Of course a replacement tube costs more than a new tv.
posted by damn dirty ape at 12:25 PM on March 15, 2007

My husband works on our TVs and monitors, because he knows what he is doing. His advice is that if you don't know what you are doing, please do not even open it up. The chance for significant injury is extremely high, and even when you do know exactly what you are doing, it only takes one small mistake to create a crisis. I know it's a hassle to take a large set to a shop, but it's really your best bet and usually doesn't cost too terribly much ... and it's much safer for someone like you who hasn't ever worked on a TV before or taken classes on the subject.
posted by Orb at 12:32 PM on March 15, 2007

Chances are, it's not going to be as obvious as a loose connection, so there's little point.
posted by Krrrlson at 12:39 PM on March 15, 2007

Ok, Lazlo...

You can get yourself killed, but if you want to know what I do when I do this....

Find service literature, if you can. Sam's Photofacts are the usual method of getting schematics for older sets. It has been a while since I had to do this, but I'd start there. It will contain disassembly instructions, safety warnings, etc. I used budget $20-30 bux for a Photofact. I don't know what they cost now.

Follow the safety recommendations in the service literature.

Unplug it. Find a place where you can work at table height. Lock up the cats, kids, dog. Don't work on it alone. Wooden floor preferable.

Unplug it again! The double check it. The danger is mostly present IF YOU LEAVE IT PLUGGED IN. Unplug it.

Turn the power switch ON with it unplugged. In many circuits, that will drain down the low voltage caps, too, but a consult of a schematic is the only way to see how your set is designed.

Danger level with an uplugged set is maybe 3 on a 1..10 scale. Danger areas are primarily high-voltage residual charge on the CRT, which can be 30,000 volts or so. BIG FRIGGING RED WIRE leading into a big suction cup looking thing on the side of the picture tube is the High Voltage Anode of the CRT. Normal process is to use a longish screwdiver, to short the electrode under that cap to a ground on the chassis. A spark will sometimes ensue, though just as often a large bleeder resistor will drain it down overnight and you may hear nothing. Usually, any shock you do get from it is akin to static, and hurts, but I've never heard of anyone getting killed by it, just cut when they pull back their hand from it in what is euphemistically called 'dangerous secondary reaction'.

The majority of the circuitry in newer, non-tube sets is very, very low voltage... 5-24 volts and presents little shock hazard.

Remove all conductive jewelry.

Keep one hand (not the dominant) in your back pocket. This will assure that any shocks do not pass from hand to hand and across your heart.

I don't wear gloves or anything when I do this. Try and avoid touching anything with your right and left hands simultaneously. If you keep one hand in a pocket, you can see this is easier to do.

I've found maybe 10% of the problems that you describe being connector or seating related. Sounds like either vertical oscillator or vertical output amp has a thermal problem. Newer sets are highly integrated and when you have problems, they often are inside chips and can't be troubleshot as in the old days.

I think it's reasonable to look inside. Of course, I have done it before and lived to tell the tale. Remember, a malfunctioning set may not behave like is should, and nothing is risk free. You can minimize, but not eliminate danger, and you are trading off risk for convenience. I share your reluctance to give up without a fight, but the safest thing to do is let a pro take a look.

Good luck.
posted by FauxScot at 1:04 PM on March 15, 2007 [3 favorites]

Lazlo, I've no answer for you, I just wanted to say that judging from the rest of the answers you probably saved my life. I have the exact same problem and I've been pondering the possibility of fixing it myself.
posted by micayetoca at 1:05 PM on March 15, 2007

Seconding micayetoca, I won't be going anywhere near my problematic set. I had no idea this was so dangerous.
posted by cashman at 1:19 PM on March 15, 2007

It's not just the shock hazard that's dangerous, it's that the "neck" of the CRT is generally it's weakest point, mechanically. I've seen an experienced broadcast engineer assigned to troubleshoot a misbehaving Tektronix 17 inch rack monitor get jolted by the flyback transformer, jerk his hand against the tube neck, thus causing an implosion of the CRT. Helluva noise, and some large peices of glass flew around that end of the control room, and the only thing that probably saved his eyes was that he was wearing glasses. As it was, he got a number of significant facial lacerations, plus glass embedded in his hand and arm.

The front of a CRT and most of the conical envelope is made of thick glass, and is pretty resistant to mechanical damage, short of gun shots. But the neck of the tube, not nearly as much.
posted by paulsc at 1:57 PM on March 15, 2007

My old Sony television started doing the same thing a year ago and I went probably six months beating the hell out of the thing because I was too lazy or cheap to go get a new one. If tapping it seems to fix it, it's more than likely the tube dying. Start looking into environmentally sound television disposal sites.
posted by mikeh at 2:03 PM on March 15, 2007

Nthing take it to a shop. If a repairman can fix if for under $100 you might get a few years more life out of it. For what it's worth, my mother has a near 20 year old Sony Trinitron CRT that still has a very nice picture when plugged into a digitally sourced signal.
posted by Burhanistan at 2:11 PM on March 15, 2007

STOP RIGHT NOW.

Taking apart a television is not something to undertake lightly. I have experience in this area.
posted by alby at 2:13 PM on March 15, 2007

I like FauxScot's answer, and though I have never heard of someone killed by the HV anode, I guy I know woke up on the other side of the room from where he was disconnecting it.

So, just as you unplug the set twice, ground the HV Anode 3 times.

And be careful in there.
posted by MtDewd at 2:22 PM on March 15, 2007

There's about a billion tv's for sale for less than $50 on SF's craigslist. CRT Televisions and printers are basically disposable now. I can't imagine bothering to fix it.
posted by muddylemon at 4:08 PM on March 15, 2007

The sci.electronics.repair FAQ on repairing televisions. In particular, Safe discharge of capacitors in TVs and monitors.

Bottom line, sure you can do it, but.. It is not at all like futzing around inside a computer though - PCs were designed for user servicing, and they are low voltage. It probably isn't worth the bother (and that is saying a lot coming from me).
posted by Chuckles at 7:42 PM on March 15, 2007

Argh! Incomplete edits strike again..
posted by Chuckles at 7:43 PM on March 15, 2007