Sony Trinitron KX-14CP buzzing noise - Page 1
Forum section: electronics / repair

author: orjanh
author_rank: Newbie
timestamp: May 15, 2020, 12:11:11 pm
content: Hi all,I got this old Sony Trinitron KX-14CP1 CRT that is making a buzzing noise whenever the video input is connected.Sorry for the bad filming - hopefully you can hear the buzzing sound:Edit: Second example:https://youtu.be/bux4hKXvNH4Does anyone know what could be causing this buzzing noise?Thanks!

author: Manul
author_rank: Super Contributor
timestamp: May 15, 2020, 01:01:10 pm
content: Does this sound come from deflection coils?It seems it is NTSC video signal, low pitch buzz is 29.97Hz frame rate and high pitch is horizontal scanlines at near 16Khz. It may be loose, vibrating coils.

author: orjanh
author_rank: Newbie
timestamp: May 15, 2020, 08:06:42 pm
content: Thanks.The signal is PAL.It seems like the buzz is coming from the board I am filming, but I am not 100% sure, it’s a bit hard to determine.I’ve reflowed the solder joints on the flyback transformer as a shot in the dark, but with no change in the buzzing.

author: vk6zgo
author_rank: Super Contributor
timestamp: May 16, 2020, 01:10:57 am
content: Sorry, no noise, or any other sound heard on the video!It is many years since I worked on one of these, but I seem to remember some acoustic noise from the SMPS on startup, so It may be worth looking there.I wonder if in this model, they synched the SMPS with horizontal rate to minimise electrical noise interfering with the video signal.(Sony didn't always do this).If so, the "buzzing " may be 15.625kHz, which is probably out of my hearing range, & the reproduction range of my iPad, so maybe why I can't hear it on the video.A good trick is to "poke" likely areas with a plastic "spudger" or something similar, to see if the noise is affected.Another one is to hold a piece of plastic tubing to your ear & use the other end to search for the origin of the noise.

author: orjanh
author_rank: Newbie
timestamp: May 16, 2020, 08:51:01 pm
content: Thanks :-)Tried a plastic spudger on the majority of the components on the PCB in question (pretty sure it’s coming from the one I’m filming). No change though.Also tried rolling up a paper sheet and holding it up to my ear, and I think the buzz is coming from the middle of that board.I uploaded a second video, hopefully it’s easier to pick up the sound in this one:https://youtu.be/bux4hKXvNH4Greatful for all tips, thanks!

author: orjanh
author_rank: Newbie
timestamp: May 17, 2020, 07:32:48 pm
content: After looking up component sounds and comparing to the one I am hearing, the closest resemblence I’ve found is a transformer like sound, as it is not very high pitched.I’ve attached two pictures of the board, and marked where I _think_ the sound is originating from. In that section of the board I can see two transformers; one small on the top part, and one quite a bit larger on the bottom part.Can someone confirm that the sound in the videos in my original post could be from a transformer?Thanks guys!

author: BreakingOhmsLaw
author_rank: Frequent Contributor
timestamp: May 17, 2020, 09:48:39 pm
content: Hi, i have worked at a Philips Picture Tube factory back in the nineties.Here are some possible causes:- check if the sound is caused by arcing. Turn out the lights, see if you can see sparks around the high-volatage transformer, the neck of the tube (theres a 3,5kV signal there for focus, commonly called Gate 3, the pin that is insulated from the others), and the wire that is wound around the aquadag (black conductive paint on the back of the tube). Do you smell ozone? (The smell of old copy machines) Arcing creates that.- it might be the degaussing circuit. Check the PTC that is in series with the degaussing coils. Unlikely though, the image in the second video is stable,active degaussing causes it to shake.- check if the noise is coming from the deflection coil.If that does not yield success, do this: get a long rod of plastic or wood, or anything that is an insulator. Press it against a part and press the far end against your ear. Use it like a stethoscope basically. Don't lean into the unit, lest you want to get to know Mr.Anode and his 21.000 volty friends.

author: orjanh
author_rank: Newbie
timestamp: May 19, 2020, 04:41:58 am
content: ThanksFound a plastic rod to use as a stethoscope, as you suggested, but weren't able to find anything.When turning off all lights, all I see is the faint light inside the "electron gun" that is connected to the neck board. I guess this is normal.Before switchingonthe video input (when there is no buzzing noise), I were able to see couple of very dim arcs over the anode cap. The arcs disappeared when I enable video input (and the buzzing noise start).About the copy-machine smell (ozone). There is indeed a smell coming from the screen when powered on. I figured it was old dust and grime burning away. But when inspecting the screen, looking for the buzzing sound, my eyes become dry and irritated every time, and perhaps this is also a sign of ozone (arcing)?Could arcing be invisible, or possibly there's internal arcing in components?The CRT was pretty dirty when I got it, when cleaning the outside of it black dust that needed some elbow work to get off. I can see that the inside is pretty filthy as well, so will try to clean as best I can. Maybe the grime and dust coould contribute to arcing? I see people on YouTube rinsing filthy PCB's in soapy water, but I am a little hesitant to do that...

author: Rasz
author_rank: Super Contributor
timestamp: May 19, 2020, 06:22:07 pm
content: how old are you? this is a normal sound of old TV

author: orjanh
author_rank: Newbie
timestamp: May 21, 2020, 12:12:10 pm
content: Have had my fair share of CRT’s growing up actually :-) I have two other CRT’s now, and they don’t make this ticking noise (B&O MX4000 and a Philips 21 inch).Will try cleaning the inside of the monitor and see if it makes any difference.Also considering buying a LCR meter to be able to measure caps around the boards.