Self repairing telly?

[Lobster]

I had stashed an old (20+ years?) 14" CRT TV stored in the garage for a few months as it was surplus to requirements, but the other day needed it and fetched it out again. If I'd thought it through properly I'd have at least let it warm up to house temperature before switching on, but I didn't. It worked fine for a couple of minutes while I was tuning it in, then went phut - the LED channel indicator went blank, and it refused to respond to any commands and the screen stayed blank. It was still powered up as I could hear a faint electrical squeaky/hissy noise from inside.

Bugger, I thought - presumably it didn't like the cold shock or damp air in the garage, followed by suddenly being warmed up. Or something.

Left it in the house for a few days, as I was going to take it down to the local tip^h^h^h recycling centre, but before I did, thought "oh well, might as well just try it once more" and I'm glad I did, as it's working perfectly now.

How did that happen then?

David

[Peter Andrews]

At a guess when you brought it inside it was cold, water vapour condensed all over the circuit boards (if you wear spectacles you will know what I mean when you go into the pub on a cold night) and created high resistance short circuits which effectively killed it. Left alone it dried out and, hey ho, worked at a later date.

Peter

[Lobster]

Well that's rather what I thought, but I assumed that any such short circuit would trash the electronics?

David

[Ian Stirling]

Sometimes.

[Newshound]

Except that it's not a dead short, and modern electronics is pretty robust. My guess it it wasn't so much the circuit boards as the high tension shorting out somewhere, and protection circuits recognising the fault so that you didn't get Frankenstein films arcing. (I go back to the days where you looked for a high tension fault in electronics (or cars for that matter) by taking them to a dark place).

[fred]

In article , Newshound writes

I had a go at fixing a telly for some studenty friends that had spilled a soft drink down the back of it during a party. It was just like Dave's with much humming and buzzing but they hadn't mentioned it to me until it finally stopped working. The HT board on the back of the tube had a grove etched in it in a Grand Canyon stylee which had been nicely metalised by the HT current flow. With the board scrubbed clean of sugary goop and the canyon scraped free of metal the telly worked like a good un, certainly long enough for it to be handed back to the rental company.

[Harry Bloomfield]

Lobster laid this down on his screen :

Your initial switch on when the TV would be internally cold plus damp from condensed moisture in the warm room, caused the power supply to trip and shut down. Powering down and back up reset the PSU, despite the two events being widely spaced in time.

[Andy Hall]

Now we know why student grants were phased out.