[HECnet] VT420 with a "worn out" display

[Ian McLaughlin]

On Oct 4, 2013, at 10:56 AM, Cory Smelosky <b4 at gewt.net> wrote:


Yeah.   I know they're in the kV range. I'd appropriate discharge the CRT itself...but I lack the appropriate HV grounding wires.


A flat-blade screwdriver and an alligator clip lead.   Clip the lead to the shaft of the screwdriver and to the metal chassis of the monitor.   Work the flat blade under the rubber cup where the anode wire attaches to the CRT.   Be prepared for a loud POP and a flash.

CRT is now discharged.

If the loud pop scares you, then you can build a resistor into the grounding lead.   I built one of these many many years ago, and it lives in my toolbox for just this event.

Please note that a discharged CRT can build up a static charge again just by sitting on a shelf.   Always re-discharge the tube when coming back to a tube you've left alone for a while.

Also, Brian's advice about the hand in the pocket is important.   Current is looking for ground.   If your other hand is holding the chassis, then the shortest path to ground is across your heart.   Not good.   From your hand down your leg to ground, while not good, is at least not across your heart.

Ian