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Refurbishing a Classic Monitor (Page 2)
By, William Stephens

Disconnect the pattern generator/videogame and the AC power connections to the monitor,

Once you have your capkit in hand, it's time to remove the chassis from the monitor frame and CRT. There are several things to disconnect, the most dangerous however is the CRT Anode wire. That's the thick wire coming from the flyback transformer and going to the CRT with a suction cup at that end. This is your high voltage lead so don't touch it right away... you may get a 20,000 to 30,000 volt shock.

You need to discharge the CRT first. I use a high voltage probe because I have one.



Most people don't have one of these, so you can fake one out of a plastic handled screwdriver and a clip lead.

Actually, the high voltage probe does more than discharge CRT's but both will work for that purpose. Clip the alligator clip on chassis ground (most any screw or hole in the chassis) and then without touching anything except the probe or screwdriver handle, push the tip under the suction cup on the CRT bell. When using the high voltage probe it will hiss and kind of sound like your letting the air out of a balloon. The screwdriver will produce a sharp "snap". Once this happens the tube is discharged... wait a minute or so and do it again just for safety's sake. Sometimes the tube will already be discharged, take no chances and assure that the CRT is discharged.

You can now disconnect the anode lead from the CRT by pinching the rubber suction cup and gently pushing side to side in order to free the connector pins which are usually like wire hooks. With the anode disconnected you can proceed to disconnect the other plugs that connect the CRT to the chassis. Start by gently removing the neck board from the end of the CRT. You will notice a ground wire attached to the neck board coming from the CRT. Disconnect this wire... these usually are connectorized, if not, clip or unsolder it from the neck board. Remember where it was connected. Next disconnect the yoke magnet connector from the main board, these can take some rocking to disengage... be gentle. all that's left is the degaussing coil connector, unplug this and you're ready to remove the chassis from the monitor frame.



Unscrewing the chassis can be a little confusing. Most monitors allow the chassis to come free with the removal of a couple of screws usually along the rear lip or edge of the chassis. In the case of the Toei, it's three screws along the rear flange of the chassis. Once these screws are removed (and saved in a safe place) you can gently and slowly pull the chassis out taking care not to snag any wires from the chassis or neck board.



At this point with a usual monitor I take time here to clean the chassis and CRT. Well used monitors are usually filthy! The high voltage attracts dust particles just like an electrostatic air cleaner. Over the years thick layers of black soot like crud are deposited all over the tube and high voltage section, this, along with a few decades of regular old airborne dust and dirt make cleaning an imperative. I do this with plain old soap and water, a spray head and some brushes to dislodge gunk between components... I give the chassis a bath. The whole trick here is to make sure it is absolutely dry before doing any electronics work or worse yet try to turn it on. Some forced air is good for getting moisture from under things like the flyback transformer and tightly packed components.

The CRT and monitor frame usually get partially disassembled and then wiped with moistened cloths. Care should be observed when cleaning the conductive coating on the outside of the CRT bell, although it's on there pretty good, vigorous rubbing can remove portions of this coating. Be careful not to do this, it will ruin the CRT. Additional care should be taken cleaning the yoke and purity ring assemblies so as not to move anything or snag the fine copper winding wires... not even a bit. Be gentle here and clean it delicately as you would a mechanical clock or watch.

Surprisingly, the Toei is almost completely clean, just a little soot on the flyback and anode wire. A few blasts of compressed air, a quick wipe and it's clean as new, no bath required. This is very unusual for a monitor of this age.


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