Entertainment Center: TVs, Stereos, VCRs and DVDs - Zenith 26" 1999

I bought my Zenith as an open box deal in May of 1999. Last night i was watching TV and without warning the picture collapsed quickly to a mostly white horizontal line in the middle about 1/4" thick for maybe 3-5 seconds and then the same kind of clicking noise as if i had hit the power off button and everything was dead. Won't turn back on at all (12 hours later at this point). It does get used frequently since my kids love PBS shows. I'd rather not be spending a lot on a new TV right before Christmas and the holidays. Thank you for your time.:)

If you feel comfortable poking around inside the set with potentially lethal voltages all around, you might possibly identify a loose connection or a bad solder joint. More likely a component has shorted (in the vertical sync section) and either taken down the power supply or caused it to protect itself by not allowing the set to turn on.

Opening the back of a TV is not something that you should attempt unless you know what you're doing. Seriously. Do you have any experience working with electronics?

Ok the next morning i cleaned off the TV and got to the plug in back. I unplugged it and heard a very quiet high pitched sound that's usually associated with the screen charging or discharging. when i plugged it back in it did it agian. I did that 3 or 4 times and then tried to turn it on and it came on fine until today. It just shut off again. So i tried the plugging and unplugging and that seemed to work again for about 5 minutes and then it popped off again. Is it possible it's over heating? The house is around 75 degrees right now and was about 77 the first time it shut off. and yes i've had some experience with electronics and with other electrical work. In fact i like the 110v buz every once in a while.

Sounds like a failing power supply. These things can be difficult to diagnose without proper troubleshooting.

With unit unplugged for at least 10 mins, remove case and inspect your power supply board for burnt solder joints. Burnt/failed solder joints are very common. Just be sure to read my FAQ Sticky about working on your own set.

The set can store alot of power at the tube neck, so be careful.

I've got the case removed right now. Does the solder joint look burnt only when plugged in? or should i be looking for carbon trails? I'll stay away from the tube neck and use the one hand rule. is there a schematic on this thing that i can get ahold of? Model # A25A11D I found the instruction manual from zenith on it but no free schematics yet. Thanks for your time by the way.

Ok there are 2 spots that i've found possible problems. One looks like it is possibly on a flat style capacitor and it is an orange ring round one of the solder joints.

The other looks like it is attached to something black plastic and cylindrical with a coil of maybe 14 guage wire wrapped around the lower 2/3 of it. The problem is that it seems to have a bad solder to it (indented instead of a nice bead on the printed surface). it also seems to have some junk crusted on it. I have pictures but don't know how to upload them.

ok one more with better lighting now. It's a discolored portion of the circuit board that looks like it may have been around some heat too long. Possible problem with a solder joint in there too. It seems like this discolored portion is located under what looks like a transformer coil. Let me know if there is somewhere i can up load pictures to.

Yea, sounds like power supply.

You can post your photos to any file sharing site like photobucket.com or somewhere else. Once they are posted there, you can post this link using this "insert image" option.

The intermittent oscillation (squealing) tells me that something in the vertical IC section is loose or failing. Could be something as simple as a corroded connector. Try reseating it. It's on the right side of the board as you look at it from the back. Another culprit could be a dried capacitor.

When I said "poke around" in the previous post, I meant it. Literally ... with one hand in your pocket, physically move the parts, connector, and large metal heat sink using a small piece of wood. That might identify a bad solder joint.

A bad solder joint could heat up and discolor the board.

http://i214.photobucket.com/albums/cc266/gumbytig/discoloredportionzoomedin.jpg
Here is the discolored area i was talking about.

http://i214.photobucket.com/albums/cc266/gumbytig/discoloredportionzoomedout.jpg
Here is the discolored area zoomed out for location reference.

http://i214.photobucket.com/albums/cc266/gumbytig/ringmarkedpossibleproblems.jpg
Here is a zoomed out of the other two possibilities.

http://i214.photobucket.com/albums/cc266/gumbytig/possibleproblemareacrop.jpg
Here is a zoomed in of the previous mentioned two possible problems.

I mentioned in previous posts about the problems with these all. Is there stuff on the circuit board that may give me lethal shocks or is that mainly on the back of the projection tube? It's been a while since electronics classes that i've taken, what do i need a heat sink to resolder and what is typically fince to solder without a heat sink? Also it seems the longer that i leave it unplugged the longer it works after that. and one last thing, the orientation of the board in the pictures is front on bottom and back on top. The TV is laying on the floor face down and the circuit board is pulled out and left in that orientation. Thanks again for your time in this. I will start poking things with a stick.

"The TV is laying on the floor face down ..."

Well, there's your problem right there! No wonder you can't see a picture! :D

IC chips don't like to be soldered without a heat sink, but it doesn't look like you'll be touching up any chips. Use a low wattage iron (not a gun!) and thin 60/40 rosin core. Wear safety glasses. I had a cap blow up in my face once and my glasses saved my eyes. Although you'll be working on the other side of the board, you never know ...

"... the longer that i leave it unplugged the longer it works after that ..."

I'd pay close attention to any caps in the area of the vertical IC. Heating can dry them out and change their values. Since you have access to the board, why not replace them? For that matter, a vertical IC is less than $10.

Also resistors, if burned, can change values and drain the caps faster or slower than they're supposed to. The problem is, if the resistor is burned you need a schematic to determine its value.

Pretty Pictures but all typical with age of this set. Could not see a problem with any solder joints.
Servicers replace power supply components in this set on a regular basis just for the symptoms you describe. The usual culprits are STR53041 "its that five legged component in your first pic." Along with N4923 the transistor in the heatsink "U" shape. Two capacitors 100mfd@50volts and 22mfd@63volts. Low ESR on the caps cause power supply failure and intermittant start-up.
Resolder the vertical IC as that is the next thing that will probably fail.