Installing A "Cap Kit"


Do NOT do this yourself!  Arcade monitors contain voltage which can kill you.  If you wish to try this then please obtain the proper professional training first.  I'm providing this information as a generalized procedure on how someone who is trained and experienced in monitor repair would replace the electrolytic capacitors in a monitor.  I wrote this in first person so that I don't refer to YOU specifically doing anything.  Don't even try to blame me for your injuries because I'm notifying you now that you should NOT do this!

Why And Where

If you're reading this then you probably already know that you need to install a cap kit but I'll explain why this is necessary anyway.  An arcade monitors control board will typically contain a dozen or so electrolytic capacitors.  Over time the electrolytic dries up, leaks out, etc. and the capacitor will eventually stop working.  Even before the capacitor stops working it will change its tolerance levels due to deterioration.

Bad capacitors cause many visible problems in a monitor.  The monitor might suffer from ghosts, warping, dimness, blacking out, smearing, jail bars, shrinking, missing scan lines, etc.  Eventually a bad capacitor will cause other components to fail also.

The first thing you need to do is obtain a "cap kit".  This is a package containing all the electrolytic capacitors you'll need to change for you brand of monitor.  There are many sources for these kits, including Happ Controls and Zanen Electronics.  I've ordered from both sources several times and recommend both very highly.  Your kit should contain a list of all capacitors that need to be replaced and will look something like this.

Discharging The Monitor

Most monitors will hold a very high voltage charge that can easily kill you.  Discharging the monitor is a MUST before touching or removing it.  You should never remove the monitor from an arcade cabinet before discharging it.  Accidents do happen!

For my method, I purchased a 4 foot piece of heavy gauge speaker wire from Lowe's.  I also purchased 2 spring clips from Radio Shack and soldered one on each end of the speaker wire.  At each end I soldered the wire to both leads of the speaker wire.  Lamp cord will work just as well but the speaker wire I used is thicker.  I used a short piece of cable so that it wouldn't be draped all over the place.

Clip one end of the wire to the monitor chassis.  Clip the other end of the wire to the larger standard screwdriver.

Next, locate the suction cup on the monitor tube.  This suction cup covers a lead (which is usually red) from the flyback transformer.  To discharge, I place 1 hand in my pocket (to keep it from touching something grounded) and use the other hand to slide the screwdriver under the suction cup and touch the connector underneath.  I'm always extremely careful to ensure that the hand holding the screwdriver is only touching the plastic or rubber handle - not anything metallic!

If the monitor had a charge, I'll hear a pop and possibly see a spark.  Although this is often startling, I try to keep the screwdriver on the lead.  Sometimes I don't hear any noise or see a spark from the monitor at all.  Some monitors will discharge themselves, especially if they've been unplugged for several days. 

Sliding the screwdriver under the suction cup.

Now that the discharge is complete, I can remove the monitor from the arcade cabinet.  I'm still be very careful because some capacitors may be holding a charge.  Before I remove a monitor, I usually take the standard screwdriver and touch it to the leads of any capacitor I can reach.  Sometimes this results in a visible discharge and a sigh of relief.  These smaller charges can really hurt!


Installing a cap kit requires some disassembly of the monitor PCB's.  I unscrew the main PCB from the monitor chassis and move it around to determine if I can get at the top and bottom of it easily.  More often than not I'll have to unplug some connectors to get the mobility I need to work on the PCB.  Since I don't have a photographic memory, I label the connectors as I remove them.  I avoid unsoldering any wires in order to move the PCB around more easily.  When removing the PCB from the chassis, it's a good idea to locate all electrolytic capacitors and try to discharge them by touching them with the grounded screwdriver.


I look carefully at the monitors PCB's for burn marks, blown fuses, broken component leads, etc.  I take a little time to brush the PCB off carefully with a toothbrush.  If any other components are broken or burned, it's always best to replace them.  One faulty component can burn up the entire cap installation when the monitor is plugged back in.

Replacing The Capacitors

I open up your cap kit and pull out the instruction sheet.  I take an inventory and make sure that I have everything before getting started.  Starting at the top of the list and working my way down, I replace and check off each capacitor as I go.  I keep the de-soldering and soldering tools both plugged in at all times.  This ensures that they're both up to the correct temperature so I'll have good connections.  I wouldn't even try doing this without a de-soldering iron!

I unsolder each capacitor one at a time and replace it immediately.  I place the old capacitors in a bag or other container immediately to avoid any confusion.  I make sure that I read the instructions carefully and observe the polarity of each capacitor as I replace it.  Switching the polarity of one capacitor can cause many other components to fail.

Assembly And Testing

When I'm finished replacing all capacitors, fuses and other faulty components, I take the time to re-inspect the PCB for bad solder connections.  I make sure that I  haven't made connections between traces that shouldn't be connected.  I make sure the solder is holding the component to the PCB properly.  I also make sure the solder is not dull looking and re-solder if it is. 

When I'm satisfied with the work, I re-assemble the monitor PCB's and plug the connectors back in.  I double check everything and place the monitor back into the cabinet or wherever I plan to test it.  I connect the power and video leads and power up the monitor.  I watch the monitor PCB carefully when I power it up and use a flashlight when necessary.  I look for sparks and smoke and check for any odors or burning.  If I have an electrical short I can often feel it in my fillings and teeth.  If you've experienced this feeling then you know what I mean.  I look to see if the tube lights up and after 30 seconds or so I check the front of the monitor for a picture.

After first installing a cap kit, I usually run the monitor for at least 30-60 minutes to ensure that its had time to get warm.  This also give ample opportunity for components to fail.