Electrical advice needed!!!

[Walkinshaw]

Hey,

I am currently building 3 cabs for friends and I am using  brand new decased 51cm TV's.

The problem is only on one of them but recently after it was working initially for a few days it seems to throw the safety switch on my house power when plugged in. I have sort of worked with it and now I can plug it into the power without tripping the safety switch but for some strange reason there seems to be a charge running through the chassis. Like for instance if I touch the composite ports on the back of the TV I get a zap. I had the audio out on the TV running into my sound card and the whole case of the computer seems to be live. I can't touch it without getting a shock.

I have taken everything out and narrowed it down to the TV unit. I only have this plugged into power now and it still has a charge if I touch the ports on the back. All other TV's are perfect.

Anyone have any advise on what I can do to fix this or test further. As I said it was working perfectly for a few days and now this.

[SirPeale]

TVs aren't isolated, so that's why you're getting that zap.  Either recase it, or get an isolation transformer.

[menace]

TV chassis' aren't isolated but the ports should be!  When you say zapped are you talking like a static zap or are you talking i just stuck my finger in a toaster zap?  I had a tv that built up a charge on the ports for whatever reason and would make a small zap but otherwise wouldn't be carrying a charge--if your ports are carrying mains power they will fry whatever you hook to them.

[Ken Layton]

Consumer grade tv sets are typically 'hot chassis' and some brands may be partially isolated and some may not. Connect the monitor to an isolation transformer.

It's also possible that your building's electrical ground connection may be going bad/corroded/mouse eaten at your main electrical panel or ground rod so you may want to have a licensed electrician come inspect your system for your safety.

[Walkinshaw]

Thanks for the replys.

The zap I mean is more like a current. There is no blue arc type zap, but if I touch the RCA ports on the back I can feel a current / charge running all the time.

The problem I have is the other 2 TV's are already installed in the cabs the exact same way. There are no metal parts touching the chassis and they are mounted on plastic feet. I just don't understand how it is perfect for a few days and the next when I go and turn it on it seems live all over. The other 2 monitors whilst plugged in I can touch the ports / computer etc and there is no charge running through them.

With an isolation transformer, I've done a little search and they seem expensive. I don't see why I would have to run one in this cab and not the others. Basically I am making these for cost to help out and my friends or I dont have alot of money to throw around.

Could the TV be faulty ? seeing the other 2 are perfect.

Would recasing stop this ? as I see it its housed in plastic so what would be the different in the housing or outside ?

As with the ports, if I connect a RCA speaker cable to them and then connect to the computer the whole computer chassis becomes like with a current.

Hope that helps more.

[menace]

if you can get your money back on the tv then i would do it--somehow live current is being shunted to the metal on the ports--how the tv still works in this condition is beyond me since your port's one side are typically grounded--I would think it would pop fuses like crazy or just cease functioning. 

An isolation transformer is usually cheap if not free--the guys around here likely have 3 or 4 in their basement--forget about shipping them though as they weigh 20-30 lbs (solid hunk of steal)--it might solve your problem but without knowing for sure why you are in the state you are in, its hard to say...

[grantspain]

have you metered out the offending voltage,sounds like maybe your getting half mains on the metal-i would be looking at an earth issue but if you have some sort of obscure short then connecting an earth to your chassis could blow the crap out of your monitor,there again in the states you have only 120v mains-not as dangerous as in europe at 240v-for instance if i have two machines next to each other and one is earthed the other not then you get 120v between the two machines metal work-not a killer but gives a nasty zap(not good for someone with a pacemaker)

[Walkinshaw]

Well it's wierd but it seems to be working now.

I got fed up with it so I packed the whole TV back into its original casing and was ready to take it back to the store. I then thought, I'll give it a go here incase it does work and I look like an idiot taking it back saying it zaps you and it doesnt happen.

Wouldn't you know it the damn thing worked fine. No zap or current coming from the RCA ports... at this point I was ready to put my foot through the tv. I then thought about how it was mounted into the cab (where the tube sits) it is a tight fit which has to allow for the degausing wire and earth wire to fit within the gap before the tube is secured in place. In some parts the degausing wire was squashed very badly between the wood and the tube. I'm not sure if this would be the problem but what I did was made the gaps a little bigger so the cables would fit through them easily.

I did that and now there is no current or charge. I'm not sure if that would even do it but it seems to be working fine now with no current running through the chassis..... NFI

The only issue I have now is when the chassis was live and I had the RCA's audio plugged into the computer, the jpac I have seems to throw up the yellow error lights and lots of them. The computer will not turn on at all while the error lights are on. I plugged another computer into the cab and the light automatically turns to green on the jpac so it seems something might of damaged the ps/2 keyboard port on the computer.... when it rains, it pours....

Thanks for all your help guys.

[subcriminal]

LOL. That was a dangerous ---smurfing--- mistake! Glad you weren't killed anyhows!