Problem with Sony KV-T25SZ8 TV when turning on

Yup, that's High Voltage arcing around in there.

Might me a good idea to have some one that knows more about it to take a look.

Ouch!

I've disconnected it from the mains. Later on today (to allow any caps to discharge) I'll take the back off and see whether there's any obvious reason for arcing - dead insects, loose connections.

Beyond that, I have the problem of deciding whether it's worth paying to repair a 10 year old CRT TV :(

Sylvia.

That would be my thought exactly.

Sylvia.

It's not worth having it fixed in my opinion..

If you can't correct the problem via a clean out, I suggest you start looking for a LCD unit.

Affects picture contents, colour and sound; could be a supply voltage. Maybe check the PSU for bulging caps.

Tony

Remember the CRT can store a nasty zap. It might be an easy fix by cleaning off the HV components. Over time to build up on HV parts I've seen airborne contaminants cause arcs. But again watch the anode connection on the CRT.

It would help if I could see where it was arcing, but like all good intermittent faults, it only seems to happen when no one's looking at the circuitry. I've given it a general clean out. We'll see....

Sylvia.

Yeah been there done that. A good wipe down with 91% Isopropyl goes a long way. Watch the anode.

Accumulated dust &/or smoke on the EHT circuitry & the back of the CRT. Take the back off the TV & see if you can see any arcing.

I would. It most likely needs nothing more than cleaning out all the gunk.

It's been a long time since I fixed my CRT TVs. But, wasn't it that the picture expanded when the HV briefly collapsed when arcing? I can't see this happening in the video.

Tony

I would expect the image to shrink horizontally &/or lose brightness during arcing.

I think there is an, albeit slight, reduction in width. Whether the brightness drops is hard to say because the colour disappears.

What I find striking is that some scan lines appear to start early, by an amount of time that is quite consistent.

It's not clear to me whether the noise is coming out of the loudspeakers, or directly from the interior of the TV.

Sylvia.

Over the years many Sony sets have had an issue with bad solder connections at the horizontal drive transformer and related parts - the drive transistor, resistors, etc. A soon-to-be-failing horizontal circuit might exhibit your symptoms.

Mark Z.

Try muting the sound then listen for the noises. If it's audible at all, arcing tends to make a hissing or crackling noise.

Does muting kill the power to the audio output amplifier, or just its audio input?

Sylvia.

As others have said, open it up and clean the area near the crt suction cup. Look under the main pcb at the print side for cracked solder joints (may have to disconnect some cables - take a picture to remember) especially in the area near the large transformer. it is a waste to send it to landfill without at least checking these common things.

-B

He meant to listen to whether any sound could be heard from inside the cabinet, with the volume down (or muted), not from the speakers.

To answer your question, muting is usually accomplished by means of a transistor placed across the input of the audio amp circuit. When turned ON, the transistor essentially shorts the input of the amp to ground. Sometimes a relay is used at the output of the audio amp to open the amp from the speaker load, although I haven't seen this done on televisions, only on larger audio amps.

Mark Z.

Isn't lifting the load from a high power audio amp asking for trouble?

Not for a solid state amp. Besides, we're talking about a television audio amp IC. Hardly high power. Virtually every audio amp or receiver over 40 watts per channel made since around 1970 uses one or more relays to control the output or protect the speakers in the event of a malfunction.

Mark Z.