Big Blue is the huge 2" in diameter blue capacitor mounted in the transformer assembly in the bottom of Atari cabinets. Since most are about 20 years old at this point in time, they have a much higher failure rate now... not that they haven't failed prior to this date... and they create a wide range of problems & should be changed. Symptoms range from not powering up at all to randomly powering up.
Update 2/03: I read in a great deal of emails about Atari woes, that should be corrected by a new Big Blue, that it couldn't be the trouble because they had recently replaced it... sometimes only a few weeks prior. Many hours of wasted time t-shooting later they discover that the Big Blue was at fault. Inevitablely, the next Q is could there be something else wrong that is causing it to die. What is happening in these cases is that they are buying surplus CG caps & they are most often as old, if not older, than the one in the game already & destined to fail prematurely. Often times the value is eroneously thought to be the cause, but any value from 26,000uf to 32,000uf should work fine. I chose to have mine made in a 27,000uf value as I think that to be the best filter for those supplies, but I have used all other sizes in that range, before finding a mfr willing to remake those, without any repercussions.
Incidentally, I chose a black wrap to be able to distinguish them from the old OEM "Big Blue". Big Blue is the name that I dubbed them with back in 1979, admittedly having IBM on my mind at that time & all the various Atari labels being blue. After coining the term "Big Blue", which incidentally I had printed right on my labels, it seems that many people all these years later seem to use it to describe a CG filter capacitor on anything... kind of defeating the purpose I had for the term. I get emails with phases like, "I need an MCR Big Blue", a "Tron Big Blue", a "Gottlieb Big Blue" and so on & so forth. Most times you can kind of figure out just what was needed, but sometimes there are multiple filters or a usage that is unfamiliar that may cause errors.
"Big Blue" : The term used for any of the large blue filter capacitors in classic Atari arcade games in the AC power supply located in the bottom of the cab with an OEM range of 26kuf15v to 28kuf15v.
Update 2/06: Three years later & I still hear the same thing over & over. My problem can't be the Big Blue because I just bought a new one 3 months ago! I know that surplus Big Blues are awful tempting with their prices running from $1.50 to $5.00 each, but they simply do not last in most cases. Manufacturing caps is not my game, so I turned to the net to see what I could find out about this & here are a few things that I found out about that I had no clue about...
Shelf life depends on the control of temperature and humidity... which should be kept as low as possible... during storage. Most mfr's recommended retesting after 5 years on the shelf. I found one that really surprised me, stating, "Even under ideal storage conditions capacitance decreases with the passage of time and therefore should be used within 6 months of delivery date to insure 100% usability. After 9 months a noticeable deterioration will begin." In one military doc I read that stored electrolytics needed to be lab tested after a 5 year shelf period & if they pass, retested periodically and in any event, disposed of as hazardous waste material at age 10.
Most of the Big Blues or other high value, low voltage CG caps found in the surplus electronic stores around the country are from 16 years old to 36 years old, so they are closer to dead than they are to life, albeit from sitting around unused. Personally, I'd rather go with the new fresh cap & be done with it over changing out with surplus over & over trying to save a buck. My guess is that over time the expense of a new cap will work out to a much better deal.
Certainly 100's, if not 1000's, of dead Atari games have been resurrected solely by replacing the Big Blue & I've heard stories of some even found by the roadside waiting for the Grim Reaper to carry them off!
Many problems blamed on the monitor are actually a result of this cap being weak or bad.
Here are 5 Big Blue Symptoms that are eroneously blamed on the monitor.