Plug, TVs or humidity?

[simba1984]

Hi guys.

I'm not an electrician, but am thinking of getting one in regarding this problem and any information or advice would be helpful.

Me and my girlfriend have managed to get through two CRT TVs (one Sharp, one Thompson), both secondhand from relatives, but caused no problems before for about 10 yrs. Both TVs suffered exactly the same problem, they began making a popping, then hissing sound and then the popping sound would occur every second accompanying flashing lines across the screen. My assumption is that a capacitor or something has blown in each of them, but it seems quite unlucky that they should both suffer the same problem just by chance.

They were both placed in multi-adapters, the Sharp was in a cheap multi-adapter from Poundland, so I thought maybe that caused the fault in the Sharp. So when we inherited the Thompson, I invested in a Homebase 6 socket surge protected extension lead, but the same problem happened again after about 6 months. The other appliances in the multi-adapters (including a Wii, Sony mini hi-fi, modem and DVD player) have always been fine.
So I am confused, could it be that our plug is faulty and damaging our TVs? Could it be the environment that the TV is exposed to- for example the room sometimes does get quite humid (from cooking or drying clothes) or could it be that we were just unlucky with these TVs?

Any guidance much appreciated. Thank you.

 

[telectrix]

i suspect the humidity could be the problem, but without investigation, it's impossible to tell if there is a fault on the fixed wiring or even the supply.

 

[RecycleElectron]

Check the aerial plug to make sure that there is not water coming down the cable from the aerial above (if it's continuous that is). This may sound strange, but some co-ax has an air spaced centre core which can channel water down the aerial lead and let it get into the back of the TV without leaving a mess outside if the aerial termination is leaking. I've seen this more than once over the years.

 

[SimpleSimon]

Check the aerial plug to make sure that there is not water coming down the cable from the aerial above (if it's continuous that is). This may sound strange, but some co-ax has an air spaced centre core which can channel water down the aerial lead and let it get into the back of the TV without leaving a mess outside if the aerial termination is leaking. I've seen this more than once over the years.

Could be on to something there Recycle. Sounds like some form of interference of the aerial.

 

[MarkieSparkie]

I'm a former TV service engineer and in my opinion it's definitely caused by moisture under the A1 EHT Anode of the CRT tube, due to the humid conditions. Do not under any circumstances try and solve this yourself, consult a professional TV engineer, as working on the CRT circuits of televisions is potentially very dangerous and can kill.

 

[WDMDL]

Humidity. 27000V DC soon finds a path through damp dust.
The CRT has a copper cating on the inside and a carbon coating on the outside of the glass at the back of the tube. It makes it into a big capacitor.
Even though the supply is only capable of a few mA at that voltage, the flashover can be a far higher current and it only takes so many flashovers to damage other, more sensitive circuitry.

Sometimes, if a TV has been stored somewhere cold and damp it is best left for a couple of days before powering up.
Even with brand new clean ones, it was recommended to give them 2 hours to get to room temp in case of condensation for this reason.

Simon.

 

[telectrix]

yep, it's around 24kv on that anode. bit of a tingler. ( was on the older sets anyway ) and it holds a charge for ages so even after switching off, it can still hurt.

 

[SimpleSimon]

I'm a former TV service engineer and in my opinion it's definitely caused by moisture under the A1 EHT Anode of the CRT tube, due to the humid conditions. Do not under any circumstances try and solve this yourself, consult a professional TV engineer, as working on the CRT circuits of televisions is potentially very dangerous and can kill.

Thanks Martie. That was a really informative supply.

 

[SimpleSimon]

Humidity. 27000V DC soon finds a path through damp dust.
The CRT has a copper cating on the inside and a carbon coating on the outside of the glass at the back of the tube. It makes it into a big capacitor.
Even though the supply is only capable of a few mA at that voltage, the flashover can be a far higher current and it only takes so many flashovers to damage other, more sensitive circuitry.

Sometimes, if a TV has been stored somewhere cold and damp it is best left for a couple of days before powering up.
Even with brand new clean ones, it was recommended to give them 2 hours to get to room temp in case of condensation for this reason.

Simon.

Thanks to you Too Si.

 

[telectrix]

think the answer then is to purchase one of those new-fangled squashed up LCD jobbies that look like they've been run over by a Transit.

 

[Marvo]

If you had it plugged into a surge suppressor it's unlikely to be a power supply problem. It still might be worth getting someone in to check the terminations in the sockets on that particular circuit and in the CU.

I'm hoping your insurance will cover your blown TV.

 

[simba1984]

Thanks for your responses. The TV is not plugged into an aerial, because we don't use it to watch television, just DVD's and the Wii. The problem has abated at the moment and the room is also less humid. This could be coincidence of course, but it would seem from your responses that humidity might be the problem.
If my girlfriend and I were to get an LCD TV (as Telectrix suggests) would this suffer the humidity to a lesser degree than a CRT?

 

[Marnik]

Yes , Humidity in CRT used to be a common problem when i used to run a repair service.
Even trying to dry em out , would not always work.From what i read on this thread, this is exactly the sympton that i would expect from a severe case of damp setting in on the CRT.

I don,t know for certain , but i assume that the new LCD screens are not so sensitive to this , as they are more solid state,and use CCFL's for the backlight,and so do not require the extreme high voltage level as used in CRT's.