Opening up a CRT TV - precautions

lukehoist

Joined Jan 19, 2015
14
2) I also read that it is not recommended to use a screwdriver to discharge?!
When I used to tinker with CRTs, for better or for worse I made the long screwdriver, wire alligator clip device described above. It worked well and I always had a gloved hand with my other hand behind my back. I was using disposable tvs from thrift shops so I didn't mid if one or two broke. On tvs that were recently plugged in there would be an arc and a pop. On many of the older set that sat around for awhile there wouldn't be any discharge. I would then keep trying to make sure before I removed the suction cup.

Also, make sure the set isn't plugged into the mains when the cover is off. It is easy to forget and accidentally touch something you shouldn't.
 

DickCappels

Joined Aug 21, 2008
10,152
If you do not need to mess with the CRT circuitry, DON'T.
A few monitors have anode voltage bleeder resistors but those are rare.

During operation, a charge large enough to give you a painful shock can soak into the glass between the inner aluminum coating and the outer aquadag coating. This charge can linger for years, even after after the anode had been shorted to the outer coating. Never touch the anode button (anode connection) or you are likely to be annoyed.
 

killivolt

Joined Jan 10, 2010
835
If you do not need to mess with the CRT circuitry, DON'T.
A few monitors have anode voltage bleeder resistors but those are rare.

During operation, a charge large enough to give you a painful shock can soak into the glass between the inner aluminum coating and the outer aquadag coating. This charge can linger for years, even after after the anode had been shorted to the outer coating. Never touch the anode button (anode connection) or you are likely to be annoyed.
After grounding with a screw driver; I would press against the clip and dislodge the cup on one side. Then with a good pair of needle nose pliers grab the cup and remove it.

A guy in the shop was walking past an old parts set in storage; the tube was exposed as well as some wires

A puddle had formed near the set from a leaky roof and his arm brush the set; needless to say he was (gumby) for awhile waiting for his muscles to start working again.

Probably luck to be alive.


kv
 

takao21203

Joined Apr 28, 2012
3,702
"Most" is a useless term when it comes to potentially lethal conditions. "Most" lightning bolts won't hit me. It's that ONE I have to worry about.
thats why you use the 1 MOHM + neon glow lamp or whatever is appropiate for you.

how about pointing out a real-world recommended procedure from a service manual?
 

MrChips

Joined Oct 2, 2009
30,714
Like others have said, I too don't wear rings, jewelry or wristwatch.

When working with HV, always put one hand in your pocket.
 

Thread Starter

hang-on

Joined Oct 18, 2014
25
Thanks guys, you are great.

In my case, I think I'll just avoid the CRT part including the suction cup. The VCR part is below the tube circuit, and is almost completely separated. When I get the stuck VHS tape out, I'll put the TV away for a while. And then, if I proceed to make a small arcade box or something, I might do the screwdriver trick. But as I do not intend to disassemble the TV, I might even get away with just paying attention to the dangerous areas. Good tip about keeping one hand in the pocket!

From all your input I gather that it is not totally crazy to tinker with an old CRT. If you take care, it will work out allright :)
 

sheldons

Joined Oct 26, 2011
613
I have been in the trade for a good 25-30 years, and was around servicing all makes and models of crt tv long before lcd and plasma sets were around.....the main danger points voltage wise on the primary side of your smps will be the main smoothing capacitor, rated at some 400vdc and up to 100uf or more.....discharging these was done with a 40w 240v lamp.....never use a screwdriver.
The ht rail (depending how long the set has been switched off) is dealt with in the same way.Crt discharging is a different matter because it is quite capable of storing quite a good charge for quite a while after switch off which can and will knock you off your feet if it catches you the wrong way (wonder how I know this?)
The way we used to discharge a crt's final anode connection was with a long bladed screwdriver which was tucked under the dag earth then moved under the rubber cap making connection to the final anode on the crt....a decent crack as it discharges is usual.obviously you dont do this with the set switched on.
Having said that with some of the older sets which had separate triplers for eht generation we did in the case of a tripping set for example disconnect the tripler and draw an arc at the line op transformer to check for the presence of eht....what model set is this ? Looks like it is a Phillips pcb thats fitted and if so the vcr section may be the famous Phillips turbo deck which I am very familiar with servicing wise as I've had quite a few to repair over the years....
 
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Thread Starter

hang-on

Joined Oct 18, 2014
25
....what model set is this ? Looks like it is a Phillips pcb thats fitted and if so the vcr section may be the famous Phillips turbo deck which I am very familiar with serving wise as I've had quite a few to repair over the years....
. Good call. It IS a Phillips TV (photo attached). Haha, I did not know that the VCR was famous :) I got a VHS tape stuck halfway in there. I think that I'll approach it with some pliers, long screwdrivers, etc., to try to gently pry/wiggle it out. What would you suggest?
 

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sheldons

Joined Oct 26, 2011
613
Nonononono...........remove the vcr section completely from the set, unplug all connectors and remove whatever metal screening there is to gain access to the vcr section. ...depending why the video is jammed in the machine depends what you find when you have access. ...you can manually unload the video tape by turning the loading motor by hand and take up the slack tape as the take up arms move back by turning the capstan motor by hand......do not force it.....you should get to the stage where the cassette can be manually unloaded in this way, if you need to the housing can be removed , but you may get into trouble on reassembly if you dont retime the deck....post pictures of the video section and the exact model you have there as they do have different decks fitted depending on model and I will talk you through it , I've got a few service manuals to hunt through.....usually your fault is an easy fix as long as you go about it in the correct way. ...
 

Thread Starter

hang-on

Joined Oct 18, 2014
25
Great! I'll look into removing the VCR section. I did not think of that. Actually I don't need it, so if I can dismantle it safely, and just keep the TV section, that would be awesome! I'll post again when the TV is home on the workbench, and I can take more pictures. For the time being, it sits in my office. Yes, my office is situated not far from the electronics trash container, and I go treasure hunting from time to time in my breaks :)
 

Thread Starter

hang-on

Joined Oct 18, 2014
25
When you get the cartridge out, feed it a PBJ on toast. It probably tried to eat the tape because it's hungry. :rolleyes:
Yeah - poor little TV. I saved him from the dumpster: All the electronics were so desparate and hungry, that they were eating each other. The printer was trying to digest an answering machine, and this little TV had turned on his old best friend, the video tape that was abandoned along with him... Neglected electronics can be so cruel! Now he is getting better, sitting on the window pane in my office. He is staring silently out in the rain, thinking about the days where he was recognized for sporting a famous VCR deck, and was in daily use for analyzing lots of video material from educational settings.
 

sheldons

Joined Oct 26, 2011
613
Sets of that era I repaired down to component level. ...they are of a better build quality than the 2 to 3 year lcd or plasma rubbish around today which are mostly scrapped because customers will not pay if say an ssb board has to be replaced and reprogrammed to suit the set , or invertor pcb changed etc....what is easier....a 25 year old set which when repaired to component level EASILY and will carry on for another 25 years or unreliable rubbish that lasts for 2-3 maybe 4 years max then not repairable and scrapped?
 

sheldons

Joined Oct 26, 2011
613
So im now awaiting the full colour pictures of your set along with the model and ill dig the service manual out if needed. ..
 
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