Refurbishing a Classic Monitor (Page 1)
By, William Stephens
(clicking any picture in this article will bring up an enlarged version)
The procedures outlined in this article are very dangerous for the clumsy and inept among us. If you think this applies to you then read but don't do, you might kill yourself.
We just got back from the Super Auction with a trailer load of junk. I call it junk because for the most part we were not certain what was included or excluded and in general we go for non-working games that we can repair and re-sell. Here's a monitor from an old Centuri Phoenix upright game. This one turns out to be a Toei CM-A20HC 19" color.
Check for the monitor make and model somewhere on the chassis like in the picture to the left. Do not use the number from the sticker on the CRT, this is the CRT's part number, not the monitors.
All of these old monitors are basically "peas in a pod" and are so similar to one another that knowing how to do one makes you a master of virtually all of them. The first thing I do is clean the picture tube face and see if there is any "burn-in", if not, then it's full steam ahead. If it is burned in then some decisions need to be made. Is it really bad? if so, you may want to toss the whole thing in the trash and get a new monitor, or you could swap the tube out with another good tube you have laying around... this is not unusual for me because I have a electronics repair shop but your situation may make this totally crazy. Regardless, replacing a CRT is kind of an art in it's own right and requires "some stuff" you probably don't have, patience will probably be the thing most needed because re-aligning a color CRT is a complicated touchy process.
The good news is that the Toei has absolutely no burn in, so it's full steam ahead.
The next thing I do is check the CRT guns. This is nearly impossible to do without a special piece of equipment called a CRT tester/rejuvenator. Sencore sell one for a couple grand but it has functionality far in excess of what's needed for these old CGA monitors. I use a nearly antique Heathkit model IT-5230 which I bought new as a kit about 30 years ago. I have had to make new connectors over the years to accommodate the types of tubes used in these videogames. I have seen these things on eBay and they would be a great buy if you could get your bid in... seems that a lot of people realize the value of these thing-a-ma-jigs. A quick check of the three guns reveals no weakness so I'm done with the CRT. If there was weakness I would go through a cleaning and rejuvenation cycle on the weak guns. This usually brings them around by vaporizing the top layer of the cathodes revealing fresh emitter material.
I don't clean and rejuvenate just because this monitor was made back in 1980. Rejuvenation obliterates some emitter material which while it does refresh the chemical surface, it diminishes the amount of emitter material available and thus shortens the life of the cathode. I want as much "life" as possible, don't you?
It's now time to actually hook the monitor up. I know most people do this first but I like to know I have a good tube before messing around with the chassis... call it a personal quirk if you like.
I use an equipment cart to carry the monitor which makes it easy to spin it around to access stuff. It also makes it easy to align the monitor facing north for purity alignments and CRT setup. First thing I hook-up is the pattern generator, in this case a Wells Gardner "Genie One" pattern generator. If you don't have one of these handy, use the videogame itself as the RGB source. It's not a pattern generator but it will supply correct signals to make the monitor light-up, and that's the only thing that's being done right now. Seeing how the monitor looks under operation.
Next, hookup the AC power. I always do this from an isolation transformer. Most old monitors will pop fuses and likely other components if you don't use an isolation transformer. If the monitor has isolation built in, using the isolation transformer in addition to the monitors isolation transformer will not hurt anything.
You may notice in the pictures above that I didn't have the correct mating connectors handy so I hooked up the pattern generator and the isolation transformer using regular old alligator clip leads. Having some of these things around is vital for quick work.
Well... in looking at the various patterns it shows that the colors are pretty correct and the purity (red screen) is very smooth and even but the sync and straightness is a bit off. Some of the chassis controls needed to be turned all the way to one side to get a marginally stable screen. The thing you don't see in these still pictures is the waviness jitter and rolling that is taking place... trust me, it's there.
From the look of this monitor and how clean it is tips me off that is was in storage for a long time, probably decades because the high voltage systems have not had time to attract much dust and the monitor has no burn in. This was a good find. Unfortunately some of the components will degrade over time, even sitting on the shelf unused. These parts are the electrolytic capacitors which dry out over time and loose their value. This type of thing is responsible for the poor sync, waviness and jitter the monitor is experiencing.
The original capacitors are probably rated at 2,000 hours operation or less. Lower life capacitors costs less than longer life ones. If you were manufacturing these things at Toei back in 1980, you would use parts that were "cost effective" if you get my meaning. 2,000 hours is about 1 year of arcade life, running for 8 hours a day. In this case, 25 years, even if the system has not been plugged in often is indeed a vast amount of time.
All this monitor really needs to become "like new" again is a cap kit. Our Cap-Kit #830406 for the Toei CM-A20HC monitor should do the trick.