High pitch noise on JVC DT-V
 

I have a DT-V1710CG that makes a high pitch noise accompanied by a slight vibration of the image.

It only happens when the set is cold and there's an input signal. It lasts for 10-15 seconds and it goes away. It really feels like some sort of vibration or "resonance".

I saw someone posting on reddit with a almost identical issue on a different set and he was saying it was the flyback vibrating. The guy solved it by sticking a toothpick somewhere underneath it to stop it from moving.

I'm wondering if anyone has any insight on what the issue could be. Any input is appreciated

High pitched noise is almost always flyback vibration. I've heard of people doing the toothpick thing before and sometimes it helps. I think it depends on exactly where the vibration is coming from (what is loose).

We used to call this "singing". Probing around with a long plastic alignment tool we would sometimes be able to locate where it was coming from. Most common causes were the flyback, yoke, and pin cushion transformers. The toothpicks sometimes worked, but also tighten any mounting screws.

I had an early 2000s 27" Sony that had a whining flyback and there was nothing that I could do about it. I think whatever was loose was on the inside of the flyback and not vibrating on the PCB

Ditto.
switch mode power supplies can sing nicely too so check that also. Plastic
probing tool good, you can also make a stethoscope out of an old
paper towel tube. The HV transformer is pretty well sealed so toothpicks
cant do much. Check the mounting screws.
BTW very nice rig !
73 Zeno:smoke:
LFOD !

For modern TV's like that, also the magnetized inductor for the S-Correction can be noisy; is very audible for normal 15kHz TV's the bad ones. For HDTV's (~31kHz) is unlikely.
Don't disregard the SMPS since even if the majority operates far higher than 15kHz, the closed loop can make oscillations and audio noise (rare, but can occur), and waveforms can have a lot of subharmonics at some pulse width.

Thank you for all the advice. I did some poking around inside the monitor, but I can't seem to find the culprit.
I tried pushing down on the Flyback and the S-correction inductor with a plastic spudger, but nothing changed. The SMPS transformer is a bit out reach and I don't have anything long enough to comfortably poke it while the thing is on, but I've checked it while the power was off and it feels really solid.

One thing I forgot to mention is that it whines only when the input is a 15KHz one. I've tried with a Dreamcast outputting 480p and I don't hear anything (although it might be that it's just "singing" at a higher frequency and I can't hear it)

At the end of the day it's not a massive deal. It's annoying but it only lasts for 15-20 seconds if the monitor hasn't been on for a bit.

Additionally, I've seen more of one time ceramic caps singing... also ferrite beads. Is worth to check it also, in the 15kHz current path.

I realized I might have messed up.
There's a ceramic capacitor next to the big boy 400v electrolytic that I accidentally bent flat wile reassembling a metal bracket on the frame (it got caught underneath without me realizing). I put it back up and it doesn't look damaged or loose, although I can't imagine getting flattened did it any good.

Could this be the cause of the "singing"? I'm not knowledgeable enough to understand the schematics and its role, but I've attached it here in case anyone smarter than me wants to take a look. C913 is the ceramic and C908 is the big electrolytic. Any help is as always immensely appreciated

PCB Pattern
https://postimg.cc/NLKYhPG8

PCB Schematics
https://postimg.cc/JGjfmffX

Photo
https://postimg.cc/0zxLNtvB

No, that cap wouldn't cause the problem.