CRT:CRT Cleaning Guide
Often times you may come across a CRT set that is dirty or has dust built up inside. Below are some guidelines for cleaning out a CRT without damaging it.
It is recommended to open any recently acquired CRT to check the inside for extreme dust build-up, as dust acts as a thermal insulator and can cause components to heat up and wear out faster. If you live on a coast, it is worth opening the set every few years to clean it out as salt in the air can build up and corrode metal components.
- Use a can of compressed air or an electric duster to blow out any loose dust. If the dust seems to just be resting on the surface and not caked on, you can use a large soft-bristle paintbrush to knock the dust off. Never use a vacuum as it risks generating static that can fry components on boards.
- If the set was out in the elements, such as in the rain on a curb or in a barn for years, you may need to wash it out.
- Remove as many components as you can besides the tube and neckboard.
- Spray down all removed components with Simple Green or a gentle soap with warm water.
- Bathe the components and use gentle swishing motions and/or a large soft-bristled paintbrush to get all visible dirt off. Alternatively, use a garden hose on a low-pressure setting to rinse it off.
- Avoid getting water on the back of the tube itself unless absolutely necessary as the Aquadag coating on it can be water soluble and come off. Instead, use a soft-bristle paintbrush to dust the dirt off.
- If it is suspected that dirt got into the anode cap, remove the anode cap (after safely discharging it) and clean both the suction cup and the surrounding area on the tube using cotton swabs and isopropyl alcohol, including any protective gel that is applied. Once cleaned, spray the anode cap metal contact with metal contact cleaner and apply dielectric grease all around the area that it attaches and plug it back in, taking care not to get any grease on the anode cap contact itself.
If the shell of the CRT set is dirty, there are a few options to clean it.
- If it has a plastic shell, you can remove the back shell and clean it using Simple Green or any other soap and water.
- If it has a metal shell, you can remove the back shell and clean it using isopropyl alcohol or WD-40. Also avoid using isopropyl alcohol on glossy coatings.
- If sticker residue is on it, use a plastic scraper. Never use a metal scraper. Avoid using Goof Off as it can eat or discolor the outer coating of plastic or metal (Goo Gone is fine).
Cleaning Signal Lines
If you suspect the signal connectors are dirty or corroded, spray some metal contact cleaner (such as CRC QD Contact Cleaner) in the ports, scrub it with a cotton swab if possible, and allow it 5 minutes to dry.
Cleaning the Screen
CRT screens are sometimes covered with an anti-glare film. It's often not clear whether your screen has a film on it or not, so you should assume it has a film on it and only use warm water and a rag to clean it. Do not use alcohol or Simple Green (which contains alcohol), Windex, or other solvents that may remove this film or the glossy coat of the bezel. If there is marker or sticker residue on it, try gentle options like dish soap or Goo-Gone before using harsher chemicals.
Cleaning Up Capacitor Fluid
If you notice a capacitor on a board has leaked electrolytic fluid or has a powdery substance near it (which may be leaked fluid soaked up by dust), you should remove the capacitor, clean the board with isopropyl alcohol and a cotton swab, and then replace the capacitor with one with an equal capacitance value and greater or equal voltage value.
See the Retrobrite page.
Cleaning the Anode Grounding Fingers (aka Fixing Arcing from the Anode to the Chassis)
In most CRTs, the return path from the anode to the flyback is made through metal fingers that press on the back of the tube. A portion of the tube is coated with a material called Aquadag that is electrically conductive. However, often times the metal fingers are part of the chassis which is made of galvanized steel. The problem is that the steel tends to corrode over time, leading to a bad contact. This can cause arcing from the tube to the chassis, because the HV potential can be up to 30 kV and will readily jump a distance of a few centimeters.
In rare cases, the Aquadag can deteriorate and may require touching up, but usually the problem is purely due to oxidation/corrosion of the fingers. To clean the fingers, ideally the metal chassis needs to be removed from the tube. This is quite involving because it requires an almost complete disassembly of the CRT. A thin layer of oxidation can be removed using isopropyl alcohol, but often times this will not completely resolve the issue. Extensive oxidation can be removed by using steel wool.
Cleaning the fingers without removing the chassis may be possible on some models, but care should be taken not to touch the Aquadag as it is very fragile and does not withstand any solvents.
If there is still arcing after cleaning the fingers, the contact can be further improved by putting a flat piece of EMI gasket between the fingers and the tube. The gasket is a very good conductor and will increase the contact surface on both sides. Be careful when selecting the gasket material in order to avoid further corrosion.