Thanks Ian All points noted. As somebody who worked for four years in a high voltage test lab I agree re precautions. Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Mr Ian Primus Sent: 22 August 2007 11:40 To: General Discussion: On-Topic Posts Only Subject: Re: Tube or not Tube Typically, from something else. Like other terminals, 12" monochrome PC monitors, and portable black and white television sets. A lot of these tubes are interchangeable. I've run across some that aren't, but for the most part, with black and white tubes, if the base fits, the neck and deflection angle is the same, and the heater is the same voltage, it's a good chance it will work. #include <std_disclaimer.h> Carefully. :) You want to be sure to discharge the high voltage first (in both the terminal, and whatever you're stealing a tube from!). To do this, attach a length of wire to the metal shaft of a flat blade screwdriver, and ground the wire to the chassis of the terminal/whatever. Hold the insulated plastic handle of the screwdriver and slide it under the rubber suction cup of the picture tube, until you feel the metal clip inside. Typically, this will be accompanied by a *CRACK* as the high voltage discharges. (Although, it is possible that the HV dissapated earlier, depends on the terminal) Do this twice just to be sure. To remove the clip, peel up the rubber suction cup, and you'll see it's a hooked clip that fits into a hole in the tube. Squeeze the clip together and gently remove it. Obviously, you'll want to disconnect the other wires leading to the tube - the base socket, and the yoke connector. Disconnect the yoke at the board, and leave it on the tube as you remove it. Unbolt the tube from the frame, and pull it out, careful not to break the neck. Also watch out for ground leads. The new tube needs to physically fit and mount in the terminal. There are two basic types of picture tube - the tubes with ears that bolt to something, and the tubes without ears, that use a metal ring to hold them to whatever. (VT100's have ears, VT220's don't). Your replacement tube must be of the same type in order to fit. The yoke needs to stay with the terminal. This is the copper coil thing on the back of the tube. Loosen the screws that clamp it to the neck of the tube and carefully remove it. Remember what way is up. You'll need to move this to your new tube. Try to get it on straight - it controls deflection, and if it's on crooked, the picture will be crooked. It's easy to adjust later though. Reassemble terminal with new tube. Cross your fingers and hit the switch. If it works, adjust your yoke for a level picture (carefully, you don't want to zap yourself). Once the yoke is level, shut the terminal off and tighten the yoke so it won't move. I have replaced the tubes in a couple things, and had pretty good luck. I replaced the tube in a VT100 with one from a PC monochrome monitor, and it works well. One time, I even swapped a worn out IBM monitor tube back into a television. It was the only TV ever with WordPerfect screen burn. And those long persistance phosphors make TV look really weird. I kept it around as a joke for a while - I said that it was a black and white TV I converted to color. (Green is a color). -Ian * Be careful messing with high voltage stuff! Keep one hand behind your back when discharging tubes, and be sure your discharge tool is properly grounded to the metal chassis of the device. There's several kV potentially stored in there. I don't believe there's enough in a terminal to kill you, but it'll hurt like hell. Best to be as careful as you can.