Properly Grounding a Decased TV

[jmike]

Hey all,
 I decased a 27 flatscreen CRT TV and mounted it for a cocktail build. Problem I'm having is that whenever I plug the TV in, the screen has a lot of static. How can I properly ground the TV, so it stops zapping me every time I touch the screen? Static goes away after a couple of minutes.   

 

[Nephasth]

Run a wire from the frame to earth (round prong of the electrical plug).

[lilshawn]

Run a wire from the frame to earth (round prong of the electrical plug).

use caution, lots of TV use a "live" chassis. be sure you plugs are wired correctly and the live/neutral is maintained throughout the system.

[Nephasth]

Shows what I know.

[ed12]

as a rule all picture tube style set's have a wire that run's around
the full out side of the tube,it attachs to the tube via springs
this is called the tube ground
as a rule it ties into the neck baord then to the chassic..
that is the proper way of doing it..
the static u feel at startup is the :degauss circuit kicking in:
with it going away after a few sec's is ok,if it lasts longer
then u are discharging the tube..
replace the ground strap as i spoke of,problem solved

ed

[jmike]

@Nephasth - no problem buddy.

ed12- It does appear that the tube is discharging as the static does continue. I do see a black wire (it's covered in black electrical tape) there is also another exposed wire they both circle all around the tube frame and one has a black connector. I took some pics to hopefully understand what I need to replace, and where to find a replacement. Really appreciate the help guys.

 

[ed12]

ok a few things here as i go
in pic6 u are holding a black wire..where exactley dose it go
beside's the bare wire running around the tube ?

second the thick black wire u are speaking of is the >degauss coil<

third u have the ground strap to far down on the tube to really be of any use to u
it should olny sit about a a max of a 1/2" down from the top
i suggest u look for a misplaced spring..there should be atleast 3 some time's 4
as that is a flat planer tube i would lean to 4

on your neck board do u have a open pin around the picture tube socket ?

ed

[jmike]

The black wire I'm holding goes to the neck of the tube see pic A
The bare wire goes around the sides of the frame see pic C and both meet up around the bottom. Also the black wire I'm holding has the connector part soldered to the bare wire. I only see 1 spring unless I pulled off the others when I decased the TV.
Adjusted the wires a bit, I was actually holding onto the TV motherboard with a zip tie and that pulled the deguass coil downward.


Thanks Ed

[ed12]

find your other spings and put them back in or find some that will do the job
u see that bare wire is YOUR STATIC GROUND FOR THE TUBE
there is no way for it work right unless it is tight to the tube around the top just where
the bell starts,if it is there it will drain off your static
about that easy
the other thing i have seen in g07's is they hooked the ground :wing's around the picture
tube ears in 3 point's and had 1 spring in place,sony did this also from time to time
it just place the ground higher up on the bell

ed

[jmike]

Thanks Ed I'll look for springs or something to make that wire sit correctly.
Don't think this was a Sony tv but it does have that bare wire wrapped around the wings of the TV, which maybe why there's only one spring.

Will test tomorrow and report back.
Thanks again


 

[ed12]

its no problem
if they are around the wing's in 3 point's with 1 spring
just try to make it fit tighter to the top of the bell
as far as u can..flat planer tubes do this all the time..
make it so your high voltage lead has nothing to do with it
even if u need to cut it free from the degause coil.
this will allow it to strech proper

a sure fire test we do is to turn unit on
looking at the back of it WITH THE LIGHTS OFF see if u see any glow's
besides the neck of the tube.
if u do u are :leaching high voltage:
thus your static if all else is right

ed

[jmike]

Well gave it a try and it's still not grounded properly.
Made sure the bare wire was completely touching the back of the screen.
It seems that even the frame is passing the current. Zap has a little kick to it. 
Thinking about scrapping this TV if I can't get the grounding issue fixed.
Also turned the light off and started the TV but didn't see any other glow besides on the neck of the TV.
Ideas? 

 

[ed12]

ok
lets do this
un-plug the degauss coil >black thing running around the back of the tube<,
trace it back to the chassic,there will be a 2 pin plug for it,un-plug it there..
then try the set.
make sure power to cab is off first though
then power cab and set back up..see if u get a zip/zap?

ed

[jmike]

Ok Ed, unplugged the 2-pin plug and turn the TV back on. It's not hooked up to a cabinet yet.
TV turns on with only a tiny zap and then zap-free.

I'm guessing I can't leave that 2-pin set unplugged so I'll plug it back in and check it again? 
Shame the wife went to bed 

[ed12]

nope nope nope
your degauss coil is shorting
what u are getting is 117vac or 220vac jolt depends on your country?
remove and replace that coil.
that little zip is fine that is normal static discharge.
this is the clue i was looking for
>It seems that even the frame is passing the current. Zap has a little kick to it<
a zip is NOT a zap
now with it un-hooked touch your chassic
there is a q behind me asking
which will be is this cabinet >isolated<?
or at least the monitor?
or did u tie the power of the monitor right into the switching supply?
without going through an isolation transformer ?


ed

[jmike]

Okay with the plugs un-hooked there is no zip or zap not even from the chassis.
The monitor is isolated meaning I'm not trying to tie the monitor into anything. It's plugged into a surge protector. Will power it on with the TV remote.
Any idea where I can buy a new degauss cable?

 

[ed12]

hmm u never really answered my question
isolation transformer is a means of isolationing the 117vac
maybe your monitor is smps style,u never really speced it or shot the board
a picture of the mother board.?
that aside,remove old degauss coil
completley,
with that in hand u have 2 choices
find a replacement,or forget about it
the degauss olny comes on for a few sec's
then shuts off auto,hence 1 of the 2 reason u feel the static,the other is the tube charging.
u can always degauss manual if needed
no fears if your colors are good and soild

ed

[jmike]

Sorry didn't know what you meant Ed.
I'm pretty sure I didn't isolate the 117vac (specially since I don't know what that means... )
I'll take some pics of the board when I get home.

Not sure what happened but I plugged the degauss cable back in last night and didn't get zapped. Touched everything including the frame of the TV. 
I'll check it again tonight but will do as you suggest either remove the degauss cable or replace it.

 

[ed12]

ok i must admit u now have me fully confused...
if u un-plugged it and olny got the normal 1-2 sec zip
then plugged it back in and got no zap/zip ?
u have me confused
i will wait for pic's of the chassic
i will want 1 that shows the ac input also
some how that chassic is getting return to the metal case..if it were hot we would not be chatting,we need to do some chking

ed

[jmike]

Yes that is correct after I plugged the degauss cable back in, no more zip or zap.
Having doubts about touching this thing now. 
Here are pics...
Pic3 shows the plug for the TV. Nothing else is currently connected to it.

 

[ed12]

ok they clear it up
that is a smps style chassic
switch mode power supply built in
no need for isolation transformer
just leave the degauss un-hooked >in case it is shorting<
hook it all the way up
i trust u are using the video/audio in's ?

btw that ground strap look's like a crows nest

ed

[jmike]

Thanks again Ed

Yes I'm using the video/audio ins.
the degauss cable is currently hooked up  but I'll unplug it.
What do you mean by "hooking it all they way up"?

This is the second time I'm trying to use this TV for a project but thankfully with all the help you've given I can continue with this build.

I owe you one buddy.     

[ed12]

>>>>btw that ground strap look's like a crows nest<<<<

ed

[lilshawn]

sorry, ive just been kinda skulking.

You don't have anything on the board touching the tube do you? often the heatsinks carry some pretty high voltages. the black (or sometimes red) coating on the back of the tube (called aquadag)is mostly conductive. if a heatsink is touching it and the heatsink is live, you can get zapped like that too. the metal tops on electrolytic capacitors can have quite a charge on them too.

[jmike]

sorry, ive just been kinda skulking.

You don't have anything on the board touching the tube do you? often the heatsinks carry some pretty high voltages. the black (or sometimes red) coating on the back of the tube (called aquadag)is mostly conductive. if a heatsink is touching it and the heatsink is live, you can get zapped like that too. the metal tops on electrolytic capacitors can have quite a charge on them too.

sorry lilshawn missed your reply.

You know I think I did. If you look at the first pics you'll see that I had the mother board zip tied to those "aquadag" black coating cables, which also pulled the spring away from the tube. Yeah, was getting a nice zap at the beginning. 

Haven't really had much time with work lately but it's been zap-free since the last time I turned it on.