It's not dead, but it has a couple gremlins, two that I know of so far.

The color purity is all screwed up, not sure yet if this is from magnets, or if the degaussing thermistor went.

I can't tune in any channels. I almost get something on a strong channel, but it's like if you play with the fine tuning knobs on an older set. It seems like the tuner is out of alignment.

The picture tube seems to be very bright. No idea how good the convergance is yet, but I can read the channel numbers fine.

Tomorrow I will test it somemore, and take some pics of it. Hopefully somebody here has dealt with this before and can help me.

I've seen similar problems on Sony's of this era. As far as the degaussing circuit goes; check the solder connections on the thermistor. I was given a 27" Sony once that simply needed it's degaussing thermistor resoldered.

The "tuner trouble" may be caused by a loose coil inside the IF can. The IF can is a small metal can located close to the tuner. It will have to be unsoldered from the chassis and the metal shield unsoldered to service it. Resolder all the little coils on that board.

I've seen similar problems on Sony's of this era. As far as the degaussing circuit goes; check the solder connections on the thermistor. I was given a 27" Sony once that simply needed it's degaussing thermistor resoldered.

The "tuner trouble" may be caused by a loose coil inside the IF can. The IF can is a small metal can located close to the tuner. It will have to be unsoldered from the chassis and the metal shield unsoldered to service it. Resolder all the little coils on that board.

There are so many boards inside this thing that I don't have a clue as to where anything is. O_o;;

I also need to remove about 20 years of dust from its inside. I'll post some pics of it tomorrow.

Was the set "thrown" in the trash or gently "set" there?
If it was tossed the shadow mask could be damaged, no repair for that except a new CRT, but let's hope for the other options.

If you have a Weller soldering gun they make a dandy degaussing coil, just power it up next to the screen and wave it in a circular motion while pulling it away, when you get far enough back that it's not affecting it anymore release the trigger.

Was the set "thrown" in the trash or gently "set" there?
If it was tossed the shadow mask could be damaged, no repair for that except a new CRT, but let's hope for the other options.

If you have a Weller soldering gun they make a dandy degaussing coil, just power it up next to the screen and wave it in a circular motion while pulling it away, when you get far enough back that it's not affecting it anymore release the trigger.

:lmao: :thmbsp:




reminds me of this year's new years find, 32" 1999 sony that needed the power supply/horiz out kit... works fine now....

If you can read the chnnel numbers fine, then convergence is fine. Also, I would definitely resolder the tuner and controller, sounds like this could be the tuning issue

Was the set "thrown" in the trash or gently "set" there?
If it was tossed the shadow mask could be damaged, no repair for that except a new CRT, but let's hope for the other options.

.

This is a Sony Trinitron. It's too heavy for most people to "throw".

Also, I believe that Trinitrons don't use a shadow mask. They use the apeture grille design.

In any case, the casing is undamaged, so I highly doubt anybody threw it.

The model of this TV is: KV-27TX20

Here's a couple pics. This one is of the back of the TV with the cover removed:
http://i119.photobucket.com/albums/o121/mrx3750/Sony1.jpg


And this one is a better shot of that side board that is attached to the frame covering the back of the CRT:
http://i119.photobucket.com/albums/o121/mrx3750/Sony2.jpg



The impression I get from this thing is that it was way overbuilt. This looks like a complex beast, and I swear that I think this thing has TWO flybacks in it!

I think the tuner section is one, or maybe both of those larger metal boxes on the side circuit board...? I have no idea where the degaussing thermistor is.

I used to have a 1987 27" Sony Trinitron TV. Sony sets of that era were built to last and be serviceable. The degaussing thermistor will likely be a small black cube soldered to the main pc board near the power supply. The thermistor itself is inside the black plastic cube. If you are going to do any serious troubleshooting on this set, you will need the Sams. They are not impossible to work on but they are complex.

Here's a shot of it working in composite video mode. The screen is the browser on my playstation 2. As you can see, the colors aren't right.

http://i119.photobucket.com/albums/o121/mrx3750/Sony3.jpg


Seeing that it does indeed get a picture, I am more encouraged to fix it. Also, I turned it off and on and ACTUALLY got a local channel to come in! Turning it off and on again made it revert back to static, with some staticy audio, but it bolsters the loose RF coil theroy.

That looks like a damaged shadow mask/aperture grill to me. The aperture grill, which functions exactly the same as a shadow mask, must be in exactly the right position to work. The heavy metal frame that's needed to keep the drill wires under tension is very heavy and easy to knock out of position. A degaussing problem usually results in a pattern of concentric circles. It's easy to drop a set with enough force to move the shadow mask out of position and not damage the cabinet. Try unplugging the degaussing coil and manually degaussing it.

I have no manual degausser.

Never mind. It's DEFINATELY the degssing thermistor! I wiggled what I thought was it, turned the TV on, and BINGO! Perfect picture!!


I'm still trying to determine where the tuner coils are. If anybody knows, I'd much appreciate the help.


I've seen similar problems on Sony's of this era. As far as the degaussing circuit goes; check the solder connections on the thermistor. I was given a 27" Sony once that simply needed it's degaussing thermistor resoldered.

The "tuner trouble" may be caused by a loose coil inside the IF can. The IF can is a small metal can located close to the tuner. It will have to be unsoldered from the chassis and the metal shield unsoldered to service it. Resolder all the little coils on that board.

You hit the nail between the eyes!

I think the IF can is the smallest of the two cans on that side PC board. Actually, I've seen several Sony's with loose degaussing thermistors. They get so hot that, over time, the solder just breaks loose from the PC board. In fact, my mid '80's 19" Sony has gotten so I can see the degaussing action on the face of the CRT after it warms up. I'm sure that's the problem with mine. I just need to get off my lazy butt and fix it. I've seen the thermistors in the '90's RCA's get so hot that they just fall apart.

The coils you need to solder are in there.

The coils you need to solder are in there.


Gotcha.

Later tonight I'll go through it and resolder the coils and thermistor.

Just to be safe, the tuner is the can that should have a coax cable running from it to the antenna connector on the rear of the set. The IF can should be right behind the tuner.

Okay here's an update:

I resoldered the degaussing thermistor, and the thing's been degaussing fine. The picture looks MUCH better now! Here's a snapshot I took of it. Compare it with the last snapshot I took of the screen.
http://i119.photobucket.com/albums/o121/mrx3750/Sony4.jpg


Now, I still have two other gremlins that need fixing.

Gremlin 1 is the tuner. I still haven't fixed that. Inside the two metal cans that Andy pointed out, one has a couple adjustable coils, and the larger one has about 50 or so copper coils!

The second gremlin is audio related. I noticed the bass is crackling badly. I checked one of the speakers and was RELIEVED to see that the foam surround had almost completely rotted away. The reason I was relieved, is that I can replace the speakers easy. If the crackling was due to an audio chip, I'd be screwed.

The second gremlin I can take care of. It's the tuner that I still need help on. Am I on the right track thinking it's the larger of the two IF can's that Andy pointed out?

The one with the adjustable coils is what I'm thinkng of. These coils should be in a tiny, square metal can with the adjustment slug on top.

Don't touch the tuner if you can help it. While I have seen them fail, they are usuallly very reliable. The IF coils are the common problem. Re-solder all the can coils and any obviously bad connections. Sony used that tuner/IF combination for years, so if you do need to replace one, it won't be hard to find.

Okay, so I definately want the smaller IF can with the adjustable coil's in it.

I'll go through it with a magnifying glass later today.

Oh yes. I also want to thank you all for your replies and helping me track down these gremlins. If you hadn't helped, I would have given up on this TV.

I just noticed that it appears to be a two tuner model. The tuner/IF on that board is probably for the picture in picture. The main tuner appears to be on the main board circled. My advice is still the same. The IF can should be the same as the first one.

While you have the main board out, you should resolder the horizontal drive transformer. It's a small transformer that connects to the B of the horizontal output transistor. This is a large transistor near the flyback. Bad soldering here started to become very common around the time this set was made. If it's bad it will cause the HOT to fail and it may take the power supply with it.

What model is this set?

The model of this TV is: KV-27TX20

EDIT: Okay here's an update:

I believe the IF can on the side board is indeed for the PIP tuner. I removed it, resoldered all the coils inside it, and lo and behold, I get channels in the PIP window. Still nothing on the main screen.

I noticed a VERY similar looking IF can on the main board, and now I know what Andy was getting at. I'll desolder it and examine it.

I'll second the opinion that the horizontal drive transformer needs to be re-soldered just to be safe. This was a BIG PROBLEM on '90's era Sony's. The loose connections short the HOT which shorts two transistors in the power supply and burns open a resistor.

I didn't see any suspect connections on the main board. All in all the soldering looks very good.

I think if it was going to fail due to bad soldering, it would have done it long ago.


I removed the tuner IF can on the mainboard and resoldered all the coils inside it, and resoldered it back to the board. No change.

I started playing with the AFT coil, and I ALMOST get a picture! Not quite though.

You might be able to swap the PIP and main IF can. There's a slight chance that the PIP IF will lack an audio ouput, but chances are it's the same. The AFT coil is a common one to have bad soldering, so double check it specifically. I've managed to re-solder every connection in there except the bad one.

I'm putting it aside for now. This thing's a tedious nightmare to work on. I might get back to it at a later date. Right now I'm so frustrated with it that I'm almost ready to rip my hair out.

What I'll probably end up doing is desoldering the tuner IF can again, desolder the AFT coil and examine it for any damage, then solder it back in.

Then I get to go through the process of getting the main IF can back onto the board which is a pain in the ass because it doesn't like to fit.

Post some pics when you get a clearer picture. Looks like you got a winner!

Post some pics when you get a clearer picture. Looks like you got a winner!

The last pic I posted of it is a pretty clear picture of the browser menu on my Playstation 2.

Keep in mind that I am using a digital camera from 2001, and that taking screenshots of a CRT is difficult to do right.

All right, here's another update:

Removed the tuner IF can from the main board yet again. Checked all the coils for bad solder connections and could find none. Put the tuner IF can back onto the mainboard and soldered it into place.


I messed with the AFT coil until I got stable audio. then I got curious and tried one of the other coils and BINGO! Got a picture! That's not the end of it though...

After hooking the TV to cable and testing every channel, I turned the TV off and unplugged it. I left it that way until it had cooled off, then plugged it back in and turned it on. The picture was messed up again. I let it sit there and warm up, but the picture didn't come back, so I started adjusting the coils again.

I got it to a state where it would have a clear picture, then wavy lines appeared and grew more prominent until the picture went out. The picture would come back a split second after going out and be nice and clear, then the wavy lines came back and grew more prominent again until the picture went out again. It did this over and over, on every chennel I tried.

So I turned it off and unplugged it again, and left it sit for 10 minutes or so, then plugged it in and tried it again. Again, no picture.

I am starting to seriously suspect that there is something else wrong, and whatever it is, it's affecting the tuner.

80s and 90s Sonys often have bad capacitors, so replace each and every electrolytic cap around the IF.

I really hate the kind of "racetrack shaped" speakers they used in this set, they sound like lifeless crap right from the start, and after a few years their foam surrounds start to desintegrate... i wonder why they didn't use a rubber, cloth or paper surround instead...

Its no wonder this exact kind of speakers are used in modern all-crap sets... but it's really disappointing to find them in an expensive, otherwise nice 80s set...

Replaced all the caps around the IF tuner. Didn't do anything.

That's it. Barring something else to try, I'm done with this TV. I'll probably end up stripping it for parts.

I'll give it a few days, and if I can't think of anything else to try, I'm giving up on this one.

It could be a defective AFT coil itself. I've seen those metal cased adjustable coils in other brand sets go bad. I'd would not scrap the set just yet. If all else fails; you could run your VCR, cable box, etc. through the AV inputs.

My intention is to eventually sell this TV. If I didn't have a better one, I would indeed use a VCR to compensate for the tuner issues.

How would a bad AFT coil make a picture come in, then go out, then come in again, as if the tuner was unstable?

To clarify what I mean: The best I've gotten it is where a channel has a nice and clear picture, then interference lines appear until the picture is overwhelmed and goes out. Then a split second later the picture comes back nice and clear again. Then the interference lines appear again and it goes out again. It does this over and over.

Is your picture going black or just blank white raster?
If it's going black you need to check the horizontal drive transformer as suggested earlier, also solder the connections on the flyback and the board on the back of the CRT.

These sets were notorius for bad solder joints.
My 1990 XBR had the horizontal issue when it was 2 years old, it took me three tries to finally find the bad connection but it's still working to this day.

No, the picture does not go black.

It's like... It's like on an older dial set, where if you turn the fine tuning dial, the picture goes out, turn it back, and the picture comes back. Only there is no dial to turn on this TV, and it does this every few seconds.

The picture is perfectly fine and stable in composite video mode. Also I checked all the transistors with heatsinks mounted to them, and their solder connections look fine. Checked the flyback as well. It's fine too.


EDIT: Here's what I'm going to do: Tomorrow I'm going to swap the main IF can with the PIP IF can. Both cans are nearly identical, and have the same amount of coils and connections in the same places.

It will tell me if it's the IF can/coil/whatever, since the PIP tuner works fine.

If it is a bad tuner/coil/IF can, then having it on the PIP board will make it a lot easier to work on, since removing that board is easy.

Sounds like you might have a drifting varactor voltage to the tuner, so check for bad solder connections and leaky caps around the microcontroller chip.

Keep in mind that an apparently good solder connecton with a barely visible ring on it is a bad one...

I swapped the IF cans. There was a change, but the picture was still drifting in and out.

I'm done with this TV. Trying to fix it has become ***FAR*** more trouble then it's worth to me. I'm going to give it to a electronics recycling center. They'll either fix it, or recycle it.

I can do no more with this patient.

I fix TV's as a hobby, and it's supposed to be fun. I sell em for pretty cheap ($10-15, maybe $20 for a decent one), because I mainly fix em just to see if I can. Trying to fix this TV is no longer fun. It quit being fun around the third time I desoldered the main IF can to futz around with it somemore.

EDIT: Okay. It's gone. Now the recycling center can do what it will with it.

screw the tuner. use the AV inputs!

Sometimes, you have to draw the line especially if you are planning on selling the TV. When I was a kid; I would almost never give up on a TV. Now, there is virtually no decent resell market on used TV's and it's really not worth spending much time or money to fix one unless you plan to keep it. I have several nice looking later model sets that no one wants. They all just sit in my building and take up space. Most people expect to get a 27" set for $25 or less and it must look new and have a 5 year warranty on it! And, you can forget about consoles & anything smaller than 25". People just don't want them anymore at any price. I still will mess with a new set; but, I usually will not fix it if it's going to cost much money. Thank goodness for junk boards.

Sometimes, you have to draw the line especially if you are planning on selling the TV. When I was a kid; I would almost never give up on a TV. Now, there is virtually no decent resell market on used TV's and it's really not worth spending much time or money to fix one unless you plan to keep it.

Yeah. Especally with the 2009 switchover to digital coming closer. I sometimes find TV's that work fine, usually sitting next to an empty box that contained a HDTV inside it.

And fujifrontier: If I didn't have three other TV's that are as good or better then that one, yes I would have hooked a VCR to it and used the AV inputs. As it is, I have a 27 inch TV that has S-video and composite inputs, a working tuner, and audio outputs as well as functioning speakers. I have another TV with all those features, and it's a 36 inch TV. The Sony had speakers with rotted surrounds, no S video, and it was a HEAVY beast!

Believe me, I tried to save this one, but like radiotvnut said, sometimes you got to draw the line.