what makes the weird crackling sound when you turn off a TV or computer CRT monitor?

Ryan Meier: Are you serious? What are you? ..... 6 years old? The crackling noise is the high voltage.... .....and yes you can get knocked on your ass from many points of the circuitry inside the television. electricitym

If it doesn't actually kill you.

"Ryan Meier" ha scritto nel messaggio news: snipped-for-privacy@4ax.com...

or computer monitor and

ROTFL !!!!!!!!!!!!!!!!!!!!! This is a troll ?

I.

or computer monitor and

I've always assumed its something to do with the deflection coils on the neck of the CRT when they have the current switched off. Then some sort of induced back-emf and consequential mechanical disturbance in the windings.Sounds a bit like HV sparking but I'm not sure it is.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

computer monitor and

OK, Here's a real answer... If there is no prblem with the TV, usually the crackling is static electricity jumping around the dust on the back of the picture tube. And yes if you touch the wrong part you can get seriously hurt (or worse) - even if the TV is off and has been unplugged for weeks! However if you read the FAQ and know how to safely discharge the high voltage it is very safe to work on an unplugged TV. Troubleshooting a TV while it is on is sometimes necessary and should be reserved for more experienced servicers because of the dangers involved.

-Mike

computer monitor and

Your not kidding there, back in the 80's when I was still in tech school I decided to fix my old tv ( I was a quite a bit dumber back then) A power resistor controling the horizontal picture cracked. The tv was an old one that still had tubes. I had the tv on and the back off after replacing the resistor and when adjusting the horizontal, I was on the side of the tv to see the picture while reaching around the back to set the pot and not looking where my hand was. I touch the anode of a 600 Vdc tube. The charge went from my wrist thru the first two fingers on my right hand. My fingers were numb for 2 days and I still carry the scar to this day. I was lucky. It serves as a reminder to me to be dam sure you know what you are doing before tinkering on something that could easlly kill you.

"Alan the Tech" ha scritto nel messaggio news: snipped-for-privacy@4ax.com...

I still remember when repairing an Hitachi set I discharged on my finger the bigger electrolytic cap, in USA it's about 150-200VDC, in Italy we have

220VAC and 300-350VDC on this cap... about 100-120uF !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Fortunately I wasn't killed !!!!!!!!!!!!!!!!!!!!!!!!!1

I.

the

I picked up a working tube amp by the chassis and the main electro. Unfortunately for me the main electro was loose and not always grounded. 400 Volts DC can spoil your whole day.

N

"NSM" bravely wrote to "All" (04 Jul 05 07:13:28) --- on the heady topic of "Re: what makes the weird crackling sound when you turn off a TV or comp"

NS> From: "NSM" NS> Xref: aeinews sci.electronics.repair:52378

NS> I picked up a working tube amp by the chassis and the main electro. NS> Unfortunately for me the main electro was loose and not always NS> grounded. 400 Volts DC can spoil your whole day.

Same thing the deflection plate drivers of an old tube o-scope. OUWCH! Don't ask me how I know...

A*s*i*m*o*v

... You mean 15" sparks are SUPPOSED to come out of this thing?!?