Sony Trinitron KV-D3411D displays no image

[polinko90]

Hi everyone, this is my first post on the forum.

I recently acquired a 34" Sony Trinitron which displayed no sound or image. I would turn it on, and I could see the green symbols when changing channels, input source, or volume, but I couldn't get an image/sound out of any device I plugged into it.



I ended up looking inside the CRT and noticed that the input board was cracked. Well, I call it the input board, but I think the service manual calls it "AV interface" it seems.






So I thought this had to be the issue, and I took it to a repair shop to solder the broken traces.



Unfortunately, it did not fix the issue but there was progress. I can now hear the sound of the PS2 menu when I plug it in via SCART or S-Video. But still no image!

So I'm posting here asking for help since I am not very knowledgeable in this area. I would like to know where I should start looking, if the issue is not just with this PCB.

Thank you!

Service Manual: https://www.freeservicemanuals.info/...Sony/KVD3411D/

[vol.2]

My first thought is that there could be more cracks. If there was one, how did it get cracked, and could it have caused something else you didn't notice. Sometimes cracks can be very hard to spot because the PCB can remain tightly in place due to screws or it could just be a partial crack and the rest of the PCB is holding the whole thing in place.

Additionally, the shop might have missed a trace, or bridged some of the repaired traces.

You need to go in with a loupe or a microscope and carefully inspect everything, and check all adjacent traces for continuity with a multimeter.

My next step would be to reflow all the solder on the whole input PCB. Those connectors, especially the SCART connectors, undergo a lot of stress, and the solder joints get broken. It is usually impossible to see that they are cold joints with a naked eye and requires a microscope to see. Reflowing has a decent chance of fixing the problem.

If that all checks out, you need to pull the other boards and inspect them all for damage.

Also possibly the cracked traces messed up something and when it was turned on, it caused something to blow up. Sometimes a missing voltage can mean death to some part or another.

Then it gets harder. You need to check voltages against values in the service manual to find a incorrect spot and hope you find one. They when you find something wrong, you have to reason why it is wrong, which can be tricky; it involves basically decoding the circuit to understand what's happening.

[polinko90]

Originally Posted by vol.2

My first thought is that there could be more cracks. If there was one, how did it get cracked, and could it have caused something else you didn't notice. Sometimes cracks can be very hard to spot because the PCB can remain tightly in place due to screws or it could just be a partial crack and the rest of the PCB is holding the whole thing in place.

Additionally, the shop might have missed a trace, or bridged some of the repaired traces.

You need to go in with a loupe or a microscope and carefully inspect everything, and check all adjacent traces for continuity with a multimeter.

My next step would be to reflow all the solder on the whole input PCB. Those connectors, especially the SCART connectors, undergo a lot of stress, and the solder joints get broken. It is usually impossible to see that they are cold joints with a naked eye and requires a microscope to see. Reflowing has a decent chance of fixing the problem.

If that all checks out, you need to pull the other boards and inspect them all for damage.

Also possibly the cracked traces messed up something and when it was turned on, it caused something to blow up. Sometimes a missing voltage can mean death to some part or another.

Then it gets harder. You need to check voltages against values in the service manual to find a incorrect spot and hope you find one. They when you find something wrong, you have to reason why it is wrong, which can be tricky; it involves basically decoding the circuit to understand what's happening.

Hi, thank you for taking the time to reply. This definitely helps me out and gives me a general idea of where to look.

[damen]

Enlarging your photo shows many traces that look questionable. It may be time consuming and not look very attractive, but running jumper wires from point A to point B may be the only option.

[zeno]

I agree with vol2. That is a nasty crack & I bet there is another.
One thing may help also. Try every input you can & see if any work.
To trace the video you really need a scope, with that it can go fast.
Voltages usually wont help unless one of the video or switching IC's
are missing VCC. Beyond that cant help much. The chassis is nothing
like the US models. Last one I worked on came from Ireland & despite
being 1/2 Irish I never got it running right !!
Bridging the break with wire is good BUT with the fine traces doing
that can drive you to the bottle

Good luck
Zeno
LFOD !

[polinko90]

Hi everyone, thank you for all the suggestions. I will look into it.

Meanwhile, I have a question to ask: I just hooked up my PS2 to an AV -> RF adapter and plugged it into the Trinitron, in the RF-in port. Once again, I only got sound. The RF port is in a different PCB, not in the one that was repaired, yet there was still no video.

1. Does this mean that the problem probably lies elsewhere, and not with the repaired board anymore? or does the repaired board deal with ALL video since it is called the "Audio video interface" ? After repairing the board I got sound, and previously I had no sound or image.

2. After this test I realized one thing I had never thought of, which is that when I'm in the channel source, it never shows any static noise... that's not normal is it?

I've tried looking for more cracks but I really can't see any.

Thank you.

[vol.2]

Originally Posted by polinko90

I've tried looking for more cracks but I really can't see any.

Thank you.

Cracks can be invisible to the naked eye and can require a microscope or other optical solution to spot.

Cold solder joints (component legs have separated from the solder) are almost always impossible to see by eye, and can even be hard to see with a microscope.

Your issue is most likely due to one or both of these things.

I suggest you first reflow all of the solder joints with some good quality flux and solder and then try again. Because your issues seem to center on the input board, that seems like a likely spot, especially because components that experience force (like connectors being plugged in and out) tend to have broken solder joints.

[zeno]

Some more ideas
1) with ohm meter check the fine traces & be they are OK.
2) see if the manual has a block diagram. That usually shows signal paths
& major voltages. Much easier than following the schematic with all
its lines.
3) for more cracks check the PCB that the cracked one plugs in to.
Most likely place to find more.
4) The big IC on the cracked PCB is switching. You can measure voltages & maybe get lucky ! The manual will tell you the settings to use to get
the right voltages.

Zeno