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Disassembling an CRT monitor

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LAN_403

lhl_henrylui

Wed May 20 2009, 10:22AM

Registered Member #1498 Joined: Thu May 22 2008, 07:08AM
Location: Hong Kong
Posts: 72

I've just got this CRT monitor and I'm going to open it.
As I'm a amateur,please tell me what safety paperation I should do and how can I safely disassemble it.
I know I have to discharge the CRT by connecting the suction cap and the ground.But I'm still afraid if there's any other dangers.Also, I want to know whether I should discharge the capacitors in the power supply circuit.Please tell me anything that is important.

big5824

Wed May 20 2009, 10:57AM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

leave it for at least a few hours after unplugging it, then id short out every capacitor you can to avoid shocks, and yes the tube can hold a very high charge so that needs shorting too.

GeordieBoy

Wed May 20 2009, 11:21AM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Along with the stored-charge hazard, there is also a risk of implosion from the CRT that contains a vacuum. Some safety tips are here:

If you aren't confident about what you are doing, then put the lid back on, and just dispose of the appliance safely

-Richie

Dr. Slack

Wed May 20 2009, 02:51PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

If you do nothing else in the way of safety, then wear a pair of safety glasses any time you are in the back of the monitor. You are unlikely to die from shocks from the caps in the TV, but a discharge, whether it causes you a shock, or whether it just makes an unexpected noise, could cause a reflex flinch that has you do something upsetting; like maybe drop the heavy tool you are holding on a weak bit of the tube. The emergency room has much better outcomes with glass in skin than with glass in eyes. Wearing them could make the difference between a story to tell your mates in the bar, and something life-changing.

Arcstarter

Wed May 20 2009, 05:14PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Yes, the CRT has enough of a charge when fully charged to really kick your butt. It would not likely kill you if you are healthy (If you have a defibrillator it is a bad idea, in other words) but why take a chance? Also some moniter flybacks have an internal capacitor that is good for apparently a few nf. That would suck!

Most of the time mine would only hold a charge of a few hundred voltage, it mostly bled off very quickly. The large electrolytics on the board should be shorted with a wire with good insulation, or just an old cruddy screw driver. I have had a few TV's and moniters that would still make quite a noise when shorted after i took them apart. Never been shocked with them though.

Wavetuner

Fri Jun 19 2009, 11:20AM

Registered Member #1500 Joined: Sat May 24 2008, 04:38PM
Location: Ojai, Ca.
Posts: 44

A little late on this one. The CRT is disigned to hold a charge and usually will for a long time. It is in essence used as a HV capacitor. To safely discharge it first thing to do, take a clip lead and strongly connect to a ground point, connect the other end to a long shank screw driver and hold it by the end of the plastic handle push the blade into the anode cap to make contact with the anode clip. SNAP. You would be stuned by that at a minimum.

We use to (With safety googles) drive a screw driver in the rear of the electron gun to equalise the vacumn. Do NOT break the neck as it can implode in and could richochete outward like a spear or so I have heard. Care must be taken if removing the yoke for this reason.

Dr. Dark Current

Fri Jun 19 2009, 11:29AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

:-D
I have disassembled a dozen of TVs and Monitors and I just always tore the suction cup off the CRT while holding the insulated part. Never got a shock. Also the implosion of newer CRT's is nothing dramatic, I think they are designed to self-contain the damage without sending any glass "shrapnels". There are a lot of videos on YT of people throwing dead CRTs from a great height and they just make a thud.

However I don't encourage anyone to do what I did, always be on the safe side, just think that TV/monitor disassembly is nothing you would need safety goggles and electrician's gloves for

KLH

Fri Jun 19 2009, 05:57PM

Registered Member #1819 Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137

When you discharge any high voltage storage device (and there are a lot in a CRT monitor), either wear a welding eye shield, powerful sunglasses, or just look away from the spark in order to avoid the risk of eye damage from UV radiation given off by the arc. Even if there isn't much radiation, it sucks to see big bright spots for hours.

Backyard Skunkworks

Fri Jun 19 2009, 07:01PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

Arcstarter wrote ...

The large electrolytics on the board should be shorted with a wire with good insulation, or just an old cruddy screw driver. I have had a few TV's and moniters that would still make quite a noise when shorted after i took them apart. Never been shocked with them though.

Its actually not very hard to make a nice dischange probe that will save your screwdrivers from getting blown up.

I generally use a piece of coathanger wire with a handle made out of several layers of polyethylene tubing wrapped in electrical tape.

A probe like that will hold up for a fairly long time and is a lot easier to squeeze into tight places than a screwdriver.

And as always, wear gloves and eye protection!

thedatastream

Fri Jun 19 2009, 07:53PM

Registered Member #505 Joined: Sun Nov 19 2006, 06:42PM
Location: Yorkshire!
Posts: 329

We used to do TVs at work years ago. We always removed the "poppie" EHT from the top of the tube by inserting a grounded screwdriver in underneath the poppie cover to discharge the capacitance before removing it.

If you are intending to dispose of the tube, you need to re-pressurise it first. Remove the tubebase board (opposite end of the tube to the screen) by carefully pulling. Look down the very end tip and you should see a glass nipple. Wearing safety glasses, use a screwdriver and a hammer to gently tap this until it cracks - you will hear a hissing as the vacuum is filled with air. Leave until it stops hissing and the tube should be much safer to dispose of (it won't work though!)

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