Dr. Scott M. Baker Restores a Classic CRT Monitor — By Polishing Out Its "Cataracts"
A step-by-step guide to fixing your own monitor's decaying glue is included, but comes with a warning not to be ignored.
Vintage computing enthusiast Dr. Scott M. Baker has brought the cathode-ray tube (CRT) monitor for an old Burroughs B21 system back from the brink — by polishing out its "cataracts."
"The monitor has a severe cataract issue," Baker explains of the problem with the display paired with a Burroughs B21 computer he's currently restoring. "CRTs are usually produced with a layer of safety glass in front of the tube. Between the tube and safety glass is PVA adhesive. Over time, perhaps worse in humid environments, the PVA will degrade. The glue will decompose and moldy specs will appear in it. This leads to a screen that is very difficult to read."
Baker compares the degradation to "cataracts," with a cloudy layer appearing around the edges of the display and working their way inwards. It's not to be confused with burn-in, where constant use of largely-static images and text at high brightness literally burns away the phosphor coating on the inside of the display — something considerably more challenging to repair.
The decaying glue, by contrast, is easier: it's not inside the tube itself, which holds a vacuum you don't really want to release, but between the actual CRT face and the safety glass facing the user. As a result, the repair is "simply" a case of detaching the safety glass, cleaning the old glue residue from both the CRT and the glass, and reassembling everything again.
Eagle-eyed readers may note the scare-quotes around "simply," there: CRTs aren't the easiest things to work on, and between the high voltages and currents they can hold even when unplugged and the risk of an implosion from an improperly-handled vacuum tube, care needs to be taken — especially when, like Baker, you're heating the display up with a combination of halogen work light and hot-air gun to break down the glue and separate the two pieces to be cleaned.
The full process is documented in the video above and on Baker's blog, but comes with a warning for those looking to take care of their own aging monitors: "dealing with picture tubes is an implosion hazard and presents a danger," Baker warns. "If you are not skilled or knowledgeable, then do not take on this task. Make sure to evaluate yourself and wear all necessary personal safety equipment."