I found a 61 inch Sony KP-61S35 rear projection TV. Upon getting it home and powering up, I saw that it powers up fine, gets a picture, but the convergence is off.

I managed to access the convergence menu and after adjusting it, I got good convergence in the middle of the screen. However, the corners of the screen still have poor convergence.

I am unfamiliar with rear projection TV's and I have no idea where to start looking.

Most projection TVs have a pair of STK ICs for the convergence outputs. These fail all the time and cause a loss of convergence.

Would their failure still allow good convergence in the middle of the screen? Also, the convergence menu works fine (I can move the red and blue and align them with the green cross in the middle of the screen to make the cross white, but the corners of the screen are still off)

I am no big screen expert by no means; but, I'll share a recent experience of mine. I got "roped in" to fixing someone's Akai (Samsung) 42" that would fire up and go into shutdown. One of the STK convergence IC's was shorted. To be safe, I replaced both of them and the set now had a picture but the blue convergence was way off. It was much better in the center than around the edges. I found that I could adjust the blue vertical lines; but, not the blue horizontal lines. The red lines would adjust as they should. I noticed that there was a mess load of 3.9 ohm, 1/2 watt fusible resistors on the convergence board (board with the STK's). I found two 3.9 ohm resistors in parallel that were both open. They checked open on the board; but, read 10 ohms and 19 ohms when removed. I guess the heat of the soldering iron must have made them fuse back together. Anyway, two new 3.9 ohm resistors and two STK's solved the convergence problem.

I too have had similar experiences. 2 out of the 3 rear projections sets I've worked on so far have had bad convergance ICs. In a Philips 46" the shorted covergence ICs caused the power supply to shutdown. In a 42" Panasonic the fault was similar to yours: Reasonable convergance in the center of the screen, but it was further and further out the closer you got to the edges. In both cases replacing the STK convergence ICs and associated fusible resistors fixed the fault.

A couple of points:

Do not adjust any trimpots before checking/replacing the convergence ICs. In the Panasonic someone got in there before me and twiddled every one of the 30 or so convergence trimpots in an attempt get a better picture. This made the job much longer than necessary. A newer set will have less or possibly no trimpots.

Clean all the old heatsink compound of the heatsink and apply a thin even coat of new heatsink compound before installing the new ICs. In the Philips one of the ICs failed because someone applied the heatsink compound unevenly. Thick blobs in the corners and a air bubble in the center, this caused the IC to overheat and fail.

There's a 43" Samsung at my usual junk auction tomorrow. It's the first rear projection set I've seen that I'd actually consider getting. It too has a convergence problem, but it looks like there is potential for a very good picture (better than any of the sets that I've worked on and various other Pioneer, Sony, Panasonic and Mitsubishi sets I've seen). Most importantly for me it's 4:3. I know I'm wierd, but 16:9 just doesn't look right to me. I can watch letterboxed 16:9 content on a 4:3 set just fine, but I cannot stomach 4:3 content on a 16:9 set no matter how it's stretched/zoomed/letterboxed.

Okay. I'll look for the convergence IC's

Could somebody tell me where to look, or what the IC's look like?

Here's a couple pics I snapped of the back of the TV with the cover(s) removed, after blowing away most of the dust inside it.

http://i119.photobucket.com/albums/o121/mrx3750/Bigscreen1.jpg

http://i119.photobucket.com/albums/o121/mrx3750/Bigscreen2.jpg


It doesn't seem overly complex, at least concerning the electronics board. Perhaps these pics will help somebody identify what exactly I have.

On another note, I can't see the image on the screen in daylight. Is this a fault of the TV, or is it the same with other rear projection TV's?

I agree on the STK chips! Indeed you can still have good center convergence because the chips are only for dynamic convergence. The center is done by the rings on the CRT necks, thus still good even with the dynamics off altogether. In your photo, the convergence chips are the two large heat-sinked ones facing you just to the left of the jack panel. Also you might check all those electrolytic caps for leakage/dryout. They can cause the chips to overheat and fail, and also the caps themselves can cause convergence issues. I don't know why the engineers put them right next to the chips, which normally get hot and cook the nearby caps.

There are probably also fuses or ICP devices in the B+ feed to those chips. Check for open. I got rid of all my later Sony manuals, so I can't look or I'd tell you where the ICPs are located. Usually 2 for each chip. There's a -35 and +35 volt supply typically to each chip, and that's where the fuses or ICPs are. Could also be glass fuses in the power supply (G-board in that model???).

Charles

Thanks for the info. Here's somemore snapshots of the STK convergence chips.

Top view:
http://i119.photobucket.com/albums/o121/mrx3750/Bigscreen3.jpg


Angled side view:
http://i119.photobucket.com/albums/o121/mrx3750/Bigscreen4.jpg


Close side view with STK number visible:
http://i119.photobucket.com/albums/o121/mrx3750/Bigscreen5.jpg


I looked the part number up, and the IC is cheap enough, and the resistors and caps shouldn't be too hard to replace. The only problem I forsee is getting under the board to desolder them.

The board the IC's are on is connected to the flyback. I have never worked with a flyback like this before, truth be told I have never discharged a flyback. I usually flip the TV upside down to get under the board. Can't do that with this TV. I'm at a loss at how to proceed.

I talked to a TV repair place, and they want around $275.00 to $350.00 to fix it!

Gah, I could buy the needed parts for maybe $20.00 at most, but I can't get under the board to replace them! There's gotta be some way I can disconnect that flyback wire without risking getting shocked or damage anything...

You have to remove the board to get to the ICs. There are lots of plug in connectors to remove, but the board should come out without too much trouble.

The anode lead on the FBT will push & turn to remove, but probably at the HVR block (not at the top of the FBT.) The focus wire should also unplug, but again, probably at the other end. Pull the rubber boot back, and carefully push and twist about 1/8 of a turn to the left. It should come out. If not, try the other end of the wire. When reinstalling, just push & click... no twist needed.

Also a note about soldering on those newer boards: Be careful when unsoldering not to burn the foil off. It's easy to do, even with a lot of experience! Use a vacuum to get as much as you can off, then use wick for the rest. It takes a lot of patience, which is one reason that the shops charge that much. I always charged a flat $150 + parts for any convergence chip job that I did under contract for TV repair shops that I worked for. And that was without having to pay rent and insurance on my own shop. If somebody will do it for $275, you might want to think about that... Remember that you may also need more troubleshooting, and then the ALIGNMENT :( . However, you CAN do it yourself if you're somewhat experienced with PC soldering.

Charles

I doubt you have to worry about getting shocked much. Projection CRTs are relatively small so they will not store a big HV charge. After a few days, the HV will have probably dissipated as well.

So... I can just disconnect the FBT wires without fear of shocking myself? Those wire's don't have 15000+ volts going through them when the TV is off and unplugged? Could somebody else confirm this for me? The more confirmation I get, the safer I'll feel attempting to do this...



As for desoldering, I have a desoldering iron, and I have successfully replaced capacitors on PC motherboards with it. If you've ever attempted it, you know those foil traces are VERY thin.

I will add that you sometimes have to "hold your mouth right" when installing those STK's. The pins are very easy to bend and it sometimes takes a lot of trial and error to get all the pins lined up to fit in the board. I'll add that $275 is a fair price for a shop to fix it. What's left around here would probably charge at least $350 for such a repair.

I'll add that $275 is a fair price for a shop to fix it. What's left around here would probably charge at least $350 for such a repair.

That's all well and good, but I don't HAVE $275.00 to fix it.

My plan is to let the TV sit unplugged for awhile, order the parts when I get the money, and disconnect the flyback wires, and the other wires connected to the board.

The TV is sitting in my garage, which is unheated. Should I worry about the cold temperatures damaging anything inside it? I can't store it in my house because of its size.

No problem on the low temp, unless you're talking 20 below or something... The coolant in the CRT assemblies is a glycol-based fluid, so it won't freeze like some of the water-cooled Magnavoxes did.

Charles

How long do you guys think the TV needs to sit unplugged before it would be safe to disconnect the flyback wires? That's the only thing preventing me from removing the board to work on the TV.

I'd like a definitive answer if possible, because I'm afraid of getting zapped.

be warned there are generic stk ic,s out there. if you buy the cheap ones it is going to bite you in the butt guaranteed. tritronics sells oem stk ic,s

I'm not concerned with the IC's at the monent.:mad: I am concerned with being able to disconnect the flyback without electrocuting myself.

I'll worry about buying good quality IC's after I get the board out of the Tv without getting zapped.

I haven't powered the TV on in a couple weeks now. I plan on ordering the convergence IC's in December. I haven't removed the board yet because I'm still wary of trying to disconnect the flyback wires. Can I be reasonably sure that I can disconnect them now?

I plan on replacing the convergence IC's, the resistors around them, and the lytic caps for good measure. I have a variable temperature soldering iron, a good solder remover, and even some desoldering wick if I need it.

I think you're plenty safe on disconnecting those HV wires.

I think I am too, but just to be safe, I'm doing it with gloves on and isolated from the ground.