It’s been about a week since the last update. Since that time, I’ve asked a few experts about the display. A few folks have mentioned replacing the “cap kit”, the HOT, and possibly the flyback transformer. Others mentioned checking the monitor chassis. A week ago I had no idea what any of this meant. Today I do.
Here’s what I know:
First of all, the monitor chassis is the printed circuit board on which the monitor components live. This sits underneath the CRT, the cathode ray tube, and larger display tube. Usually, if these old displays go bad, it’s because of a bad component on the chassis.
If you want to fix the monitor, you typically need to order new parts and replace the old ones on the chassis. I’ll get to the parts in a minute, but first a word about working with the chassis. The chassis is hooked up the big display tube itself, what we typically think of when we think of TVs. That big tube holds a lot of charge in it. To work with the chassis, you must remove it from the tube, but before you do that, you must safely discharge the monitor. If you don’t discharge it safely, you may end up discharging through your body, which could either be just painful or possibly lethal. There lots of good tips online on how to do this, so be sure to read up on it before attempting any repairs yourself.
What a “cap kit” refers to is a a new set of capacitors. If you know what type of monitor you have, you can order a new set of capacitors, or “caps”, for it. Capacitors look like little cylindrical batteries. They will typically expand or leak over the years, so it’s a good idea to replace them. If you inspect the chassis, you may find brownish-yellow goop around the base of capacitors. This may mean they have leaked. Other capacitors may also have a bulge at the top. These may also be bad. From what I understand, replacing caps will typically fix issues with bad keystoning in pictures and bad vertical or horizontal alignment.
The HOT refers to the Horizontal Output Transistor. This component is often placed near the flyback transformer (see below) and is usually situated beside a heat sink. I’m actually not sure what problems result when an HOT is bad.
Finally, the flyback transformer takes the input voltage for the monitor and essentially steps it up to several thousand volts. This voltage is applied internally to the display tube. When the flyback is bad, I think the display doesn’t even show anything. You also won’t see any “neck glow” (i.e. the cathode ray tube itself won’t glow when powered on).
There are also integrated circuits (i.e. chips) that may be bad on the chassis. They may also be bad on the “neck board”. That’s yet another circuit board that hangs off the back of the CRT.
That’s a quick summary of all the parts I know of at the moment. Hopefully it will be useful to someone doing a search online…