Saturday December 7th, 2019
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By Al Warner & Rodger Boots
Additional information was provided by: Paul Frazee, Tony Berry, Steve Zeuner, and Bob Roberts
It came to me (Al) one day while reading the Arcade newsgroup that I have never seen a full text on how to install a "Cap Kit". I guess that you may be wondering what my credentials are for telling you this. OK, in college I took a class in Circuits, I think it was called Circuits I. I did so horrible that I had to withdraw in fear of my GPA. With that behind me I knew that electronics were not for me as a profession. I took a class in programming, did a lot better.
I wrote this document as a series of e-mails to people who were having problems with their monitors in their video games. I have been pretty successful getting my monitors to work decently. It is still the part that I hate the most in a video game.
A little history as I know it.
Two things may have / did occur. Time "Dried out" the electrolytic capacitors in your monitor making their capacitance reduce. Without the capacitors doing their job you get problems like wavy picture, jail bars, smearing, warping, etc... The other thing that occurs is that over the years the solder joints at connectors develop little cracks in the solder. These cracks reduce the surface area that the electricity can flow over and sometime stop it completely. The best way to fix this is to remove the old solder and resolder the connectors, preferably with 63/37 electronics solder (available at Radio Shack). This is called reflowing. I've fixed two boards by simply reflowing the connector pins and never replacing a single component.
First thing you need is a "Cap Kit"
There are few sources for these, the one way to get one is to make one yourself. Go out to an electronics store and buy all of the Electrolytic capacitors that your monitor has. Chances are that unless you have a whole bunch of the same model monitors, this is gonna be a pretty expensive. My favorite source is Zanen Electronics, Phone 806-793-6337. They sell kits with just the parts you need based on the model monitor that you have. Just look at your monitor and there should be a sticker on it to tell you what model it is (do NOT use names and numbers found on the picture tube as these only apply to the tube itself, not the actual monitor). Some common model numbers include the Electrohome GO7(-CBO), Wells Gardner 19K6100, Wells Gardner K4900 series (Any monitor that's number has a K49 in it, I have a K4901). Call up Zanen and get the kit you need. They AVERAGE about $10.00 with shipping, some higher, some lower. Bob Roberts also sells some cap kits including ones for the GO7 and the Hantarex monitors. Note: Some electrolytic capacitors may not get replaced. The ones that don't get replaced are ones that don't carry enough current to have gone bad. Don't get concerned about it, let the cap kit instruction sheet be your guide.
"Got the kit, I'm ready to fix this darn thing"
You'll need a couple of hours, some heavy wire (lamp cord will work fine), some basic tools including a 30 watt max soldering iron soldering iron, some screwdrivers and/or wrenches, a pair of wire cutters (I like the Radio Shack "Nippy Cutters") and a little courage (trust me on this part). Use of a higher wattage soldering iron can cause the solder to "boil" and pop, sending flux and solder all over; it can also harm some components. This really is a pretty easy job!
"Warning: Scary part coming up!"
You will have to deal with the anode, that's that thick wire that goes to picture tube that has what looks like a suction cup on it. The other end is attached to what is commonly known as a "Flyback Transformer". Your problem is that this anode is connected to the tube that can have over 30,000 volts of energy stored up in it. "Uh-Oh, that sounds dangerous", it is. The safe thing would be to get rid of that charge. Get your checkbook out, you need a very expensive piece of equipment to do this. Matter of fact, I'm not sure they make them anymore. April fools (if it is not April where you are, just read this again in April). Actually this is where that Lamp cord comes in. Now I don't want to scare you, but this will be releasing an average of 20,000 volts of power from your tube. If you take precautions, everything will be fine.
"Warning: Scary part has arrived!"
Get a 3 ft. length of lamp cord, strip 1/2" off each end and attach alligator clips to the ends. (kind of looks like midget jumper cables, except that there is only 1 clip on each end!) Clip one end to the metal chassis of the monitor, and the other end to the shaft of a very long, thin, plastic or rubber handled screwdriver. With the power off and EVERYTHING unplugged, AND your free hand in your pocket, slide the screwdriver under the suction cup of the anode until it almost contacts the metal clip (try not to scratch the glass). There will usually be a "snap" sound as the charge leaves the tube. Wait 5 minutes or so and do it again. If you don't hear anything the first time, no need to wait and retry. Many monitors lose their charge on their own. It's a little frightening the first couple of times, but the thrill wears off.
The alligator clips are optional, some recommend that you don't use them in fear that they will fall off during the procedure. You can just wrap the exposed wire around the screwdriver and around the metal chassis. I don't use alligator clips, but I wear a rubber glove (wimps do this, wimps who don't want to take the charge).
Undo the Anode!
After the tube is discharged you can SAFELY remove the anode. It is clipped to the monitor, you can squeeze and rock it back and forth to get it off of the tube at the suction cup thing. I usually use the screwdriver with the lamp cord still attached (to both places) to squish it together.
It's Outta There!
Remove the board(s) by disconnecting all of the plugs and unscrewing them from the metal chassis. Remember where the cables went and how they are oriented so you'll be able to reconnect them when you put it back together. Feel free to label them if necessary. One of those handy Polaroid cameras are also good for this.
Most chassis can be handled without fear of being bit by residual charge. Bob Roberts points out that if you are installing the cap kit into a dead Electrohome GO7 monitor with a blown F901 fuse, be sure to short across the fuse as it will be storing a large painful charge. Shorting across will save an ohmmeter as well. If you test with an ohmmeter, the cap C904 (where the charge is stored) will release it's charge into the ohmmeter causing damage.
Let's start by resoldering some of the "Pins". Wherever there is a cable attached to your board there are "Pins" that that a plug plugs onto. Over time, the connections weaken and you get the kind of flakiness you may have been seeing. Resolder ALL of the pins from the back of the board. Remove the old solder using desoldering wick or a solder sucker, and resolder with new 63/37 solder. This is VERY IMPORTANT. This fixes many a problem in old XY monitors.
Capacitor markings and Orientation
The caps are marked - or + (usually -). Match up one of the caps you have to one of the the ones on your list by it's size markings. Usually look like 100uF 160V as example. The chart that came with your kit has them listed with numbers next to them. Search the board(s) and find the matching numbers. Check the polarity on the existing cap (there is a thick bar on the capacitor, 75% of the time, it's the - side), sometimes they mark it on the board too. The + side of a cap has a longer lead. The holes on the chassis are usually marked in some way, usually a dot over or near the hole. There are several monitors where this dot indicates - position. others it's +. Hantarex uses a half moon darkened spot for + on the chassis. Sometimes there is just a + marked on the board. WARNING: There is one capacitor on an Electrohome G07 monitor where the polarity is marked wrong on one side of the board . The Zanen instructions will warn you about this.
To remove a capacitor, heat the solder and use a solder sucker or de-soldering wick to remove solder from both of the holes. The cap should virtually fall out after you do both sides. Replace the cap with a new one (The polarity is EXTREMELY IMPORTANT) and bend the leads over at about a 45 degree angle to hold the capacitor fully in place. Check off the capacitor as having been replaced on the parts list sheet as you go so you'll know which have yet to be replaced. At that point you can either solder the individual part or wait until you've installed a half dozen or so and do them all at once. The long leads will show you what needs to be soldered. Clip off the leads after you have installed them all. ONLY clip ones with good solder joints. This provides a convenient check and double check of what needs to be done. Do them all (most kits have about 20).
"Wait a minute, what are these metal thingys?"
Some of the X/Y (vector) monitor kits come with deflection transistors. These things look like bottlecaps with two ears on them with screwholes. They are a little bit different to change than a cap. First, you remove the screws from the old ones and pull the transistor off. They need to be insulated from the metal that usually sit on. To do this, you need some silicon insulator grease (heat sink compound, available at Radio Shack or any TV supply store) and some insulator material. Clean off the metal surface that the old transistor was sitting on using ammonia or rubbing alcohol. Then apply a very thin layer of grease. The object is to fill the microscopic pits in the metal and insulator to allow maximum heat conductivity. If you put on too much on you will actually reduce the heat conduction. Now put on the insulator, then another thin coat of grease. Now, put on the transistor (they only go on one way) and screw it down. If you own a meter, do a continuity check between the outside of the transistor and the metal. You don't want a short! Remember, this is all about heat conduction.
Some additional notes from Rodger on insulators:
Insulators can be polyimide (a very thin yellow plastic), mica (translucent white), elastomer (gray rubbery and very flexible), and beryllium oxide (white solid). The beryllium oxide is the best but is extremely dangerous to work with. The dust from scratching or breaking it is a health hazard. You won't normally see this used in commercial equipment.
The elastomer type is my personal favorite. If you are lucky enough to be using this you can forget the grease. Ungreased it works as good as greased mica. With grease it works as well as beryllium oxide.
Mica is the most common. It will break if flexed too far (so don't do that!). You need to grease it to get good thermal transfer, but it works very well and is a real good insulator.
Polyimide probably won't be seen much. It is my least favorite because the slightest burr on the metal surfaces will poke right through it and cause a short. It also requires grease.
"We're almost there, I can Feel it"
Replace the boards, attach the anode (I usually do the discharge again to make me feel better) and other cables. Power it up. Often, when new people do this, they have a tendency to watch the screen when they power back up, sometimes not seeing smoke or a sizzling cap that they might have reversed. They then panic when they hear a pop. Replace any caps that pop due to being installed wrong.
I'd guess you can do this in an hour if you're good with a soldering iron. I don't have to tell you to be careful with your soldering and not "splash" anything. There is a good guide to electronics on the web with soldering instructions at: http://www.rmplc.co.uk/eduweb/sites/trinity/elec2.html if you need a refresher.
Disclaimer: All information is provided "as-is". We assume no responsibility for it's accuracy or your safety. Please be careful when following these procedures, they have worked well for many, your actual milage may vary.
See my homepage at Al's Arcade
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