The Arcade Video Game CRT Monitor Isolation Transformer

 

Hi!  The purpose of the CRT (cathode ray tube or picture tube) monitor's isolation transformer is simple - to keep us from killing ourselves.

Unlike an old CRT computer monitor, the CRT monitor inside an arcade video game is not enclosed within a non-conductive grounded case.  Hence, all the high voltage components and circuits are exposed.

 

Usually, if you are grounded and touch an exposed high voltage circuit, you will get painfully electrocuted, or much worse.  You can think of the job of the isolation transformer as converting high voltage to low voltage.

Actually, the isolation transformer converts 110 VAC, say, 20 amp primary line voltage to 110 VAC 1 amp secondary voltage.  You would still get shocked if you touched a CRT monitor's hot circuit, but probably not too much worse.

Basically, the isolation transformer allows a service technician to work around a video game's CRT monitor while the cabinet power is on with a degree of safety from electrocution.

 

So, here is some important information to help you recognize and properly use an isolation transformer:

 

1.  An isolation transformer is small, but very heavy for its size.  That is because there are lots of tightly packed copper wire windings.  Consequently, the isolation transformer will be mounted to the floor of the cabinet.

2.  Over time, the operating temperature of the isolation transformer will cause the copper wire insulation to become brittle and crack.  If a short occurs, the cabinet fuse will blow.  If the cabinet fuse is faulty, too large, or has been bypassed, the isolation transformer will overheat, smoke, and possibly cause a fire.

3.  Rodents are attracted to the warmth of the isolation transformer.  They like to build nests in its vicinity.  And, they like to chew on the copper wire insulation.  All of which adds up to a potentially dangerous situation.

4.  If you notice that any of the windings or insulation has discolored, cracked, and/or blackened, that is an indication that the isolation transformer is operating too hot.  Such a defective unit should be immediately replaced.  By the way, the copper can be recycled.

5.  Isolation transformers come in a variety of sizes, but their appearance and shape are somewhat standard.  Here are photos of two typical isolation transformers - 

 

 

 

6.  Usually,  on only one side of the isolation transformer there will be two or more tabs (lugs) at the bottom, and two tabs at the top. 

Two of the tabs at the bottom, sometimes identified as 110 or 115 VAC primary input and neutral, connect to the cabinet VAC power source. 

The two tabs at the top, sometimes identified as VAC 1 amp secondary output, provide VAC power to the CRT monitor.

7.  If you are upgrading your cabinet to an LCD monitor, you should remove the isolation transformer from the VAC power circuit, as it is no longer needed.  And, it could become the source of future problems.

To disconnect, simply remove the two VAC primary power leads attached to the two bottom tabs of the isolation transformer.  These two VAC power leads could then be used to provide VAC power to the LCD monitor.

 

Questions?  Send me an email:  [email protected]