365... Tech

Maybe this will help. The large transistors you mention are probably not the problem. More likely you have a problem somewhere else. A common problem here is fractured solder joints on the connector pins. UNDERSTANDING DIODES AND TRANSISTORS By Randy Fromm Do you remember when you first started working on games? Remember when you didn't even know what a transistor was, let alone how to test one to see if it was good or bad? Now that you've been working on power supplies and monitors for a while, you probably can't recall a time when you didn't know how to test transistors and obtain substitute components. If you can call to mind the difficulty of those early days, you'll understand why I occasionally take a step back and take a look at some of the fundamentals of troubleshooting. Of these basic skills and procedures,  none is more important than the ability to test transistors. If you are already familiar with transistors, this discussion will probably be a complete bore. Consider yourself fortunate to possess such a vital skill and move on in the magazine. I'll catch you next month. Still here? That's good because you just gotta learn how to test transistors. It's really the whole basis for troubleshooting monitors, power supplies, redemption games, jukebox amplifiers and a host of other things electronic. The basic philosophy is simple. Since many circuit faults are caused by transistor failure, we don't always have to know exactly how the circuit works in order to repair it. All we have to do is test the transistors in the circuit and replace the ones that are bad. Since transistors all test the same (with a few exceptions) once you've mastered the test you can fix just about anything! Diodes We use the diode test function of the meter to test both transistors and diodes. Let's take a quick look at diodes first. The diode is the simplest semiconductor that we have. The schematic symbol looks like an arrow with a bar at one end. The arrow symbol makes a lot of sense since a diode is a one way gate for the flow of electric current. It's kind of like the turnstile at a supermarket or amusement park where people are allowed to move through the gate in one direction only. A diode has just two component leads. They're called the anode and the cathode. It's interesting to note how the diode actually works inside. Just about all of the diodes we use in games are made of an element called silicon. In its pure form, silicon is an insulator. It cannot pass any electric current through itself. During the manufacturing process, small quantities of impurities called dopants are added to the silicon. The addition of the dopants cause a change in the structure of the silicon atoms. When phosphorus is added to the silicon crystal, extra electrons are added to the silicon. This gives the silicon a net negative charge, with some free electrons scooting around inside the crystal. We call this type N silicon; N for negative. When boron is added to the silicon, it develops a net positive charge. We call this type P silicon. We can think of type P silicon as having atoms with holes in the electron shell, just waiting for an electron to fall into it. In fact, we call these atoms in the type P silicon holes. The diode is made from a single chip of silicon. One half of the chip is type P silicon; the other half is type N silicon. Where the two types of silicon come together, we have something called the PN junction. The PN junction acts as a kind of barrier to prevent the free electrons in the type N silicon from reaching the holes in the type P silicon. When we test diodes and transistors, we will actually use the meter to test this PN junction. Your ability to test this PN junction will enable you to repair more electronic equipment than any other single test you will perform!! It takes a certain amount of voltage to push aside the PN junction and allow current to flow through the diode. It takes an average of .7 volt to break down the PN junction and allow current to flow. Let's hook up this diode and see how it works. The anode is connected to the positive side of the battery. The cathode is connected to the negative side of the battery through the lamp. The electrons are repelled by the negative side of the battery toward the junction and the holes are repelled by the positive side of the battery toward the junction. Where they meet at the junction, the electrons fall into the holes. This pushes the PN junction aside and current flows through the diode. If the battery is reversed, the holes and electrons are attracted to opposite ends leaving pure silicon as an insulator between them. The silicon insulator prevents current from flowing through the diode. This is why it is called a semiconductor. Sometimes it conducts; sometimes it doesn't. It takes around .7 volt to break the barrier at the PN junction. This .7 volt is used up inside the diode as the energy required to push the current across the PN junction. We call this .7 volt the JUNCTION DROP. A normally operating silicon diode will have a JUNCTION DROP of between . 45 and .9 volt when measured with most digital multimeters. Most engineers and technicians use the average of .7 volt when discussing the JUNCTION DROP. Generally speaking, the larger the device, the lower the JUNCTION DROP will be. We can test this JUNCTION DROP with our meter. There is a special setting on the meter called the diode test. When we use the diode test, we are actually measuring the voltage required to get through the PN junction. What we should see is a normal JUNCTION DROP with the red lead on the anode and the black lead on cathode (diode conducting) and OPEN when the leads are reversed. This means that the diode is doing its job as a one way gate for current. When we read a normal JUNCTION DROP it means that current is flowing through the diode. When we read OPEN, the diode is blocking the current. It's obvious when a diode is bad. If we get a reading in both directions,  the diode is shorted. In fact, most diodes short when they fail. I'd say that 99 out of 100 diode failures are short circuits. If the meter shows OPEN in both directions, the diode is open. You can usually tell if a diode is good or bad, even when testing diodes in-circuit. Needless to say, if you test a diode in-circuit and it appears to be bad, you should test it again after removing it from the circuit just to be sure. Diode Specifications A diode is rated by voltage and current. The voltage rating of a diode is the maximum amount of voltage that the diode can block without breaking down. The voltage rating is listed as PRV (peak reverse voltage) or PIV (peak inverse voltage.) The current rating is the maximum amount of current that the diode can safely pass without getting too hot. Believe it or not, we use the letter I to represent current. Huh??? Early experimenters thought of current as intensity, so the letter designation I has remained with us. Io means output current. When substituting diodes, you can always use a diode with a higher voltage and/or current rating. Remember, the voltage rating of a diode has nothing to do with the voltage the diode is putting out. It is simply a rating of the maximum voltage that the diode can block. You can replace a 50 volt, 1 amp diode with a 400 volt, 1 amp diode. You could also use a 50 volt, 3 amp diode or even a 400 volt, 3 amp diode as a replacement. Transistors Transistors come in a lot of different shapes and sizes. The packages we commonly see in games are TO-3, TO-220, TO-218 and TO-92. There are two general types of transistors: NPN and PNP. Both are named for the way they are made. They're kind of like a sandwich with type N and type P silicon. The schematic symbol for the two types of transistors is basically the same. Notice that the arrow points away to designate an NPN transistor while the arrowhead points toward the center of the schematic symbol for PNP. Since we're talking a lot about P's and N's here, chances are pretty good we're talking about a PN junction somewhere. In fact, each transistor has two junctions. The NPN transistor is made of a single chip of silicon that has one area made of type N material, a thinner region made of type P silicon, and another N region on the other side. The PNP transistor has N silicon in the middle, surrounded by P silicon. A transistor has three leads and each lead has a name. They are the emitter, _base_, and collector. There are two PN junctions in the transistor that we have to test . One is between the _base_ and the emitter.  The other is between the _base_ and collector. It is the same test we used for the diode but we'll check two junctions instead of just one. TESTING TRANSISTORS Regardless of what type of package they're in, transistors will pretty much all test the same way. You'll need a digital multimeter with a diode test. 1. Set your meter to the diode test. 2. Connect the red meter lead to the _base_ of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between .45v and .9v. A good PNP transistor will read OPEN. 3. Leave the red meter lead on the _base_ and move the black lead to the collector. The reading should be the same as in step 2. 4. Reverse the meter leads in your hands and repeat the test. This time, connect the black meter lead to the _base_ of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between .45v and .9v. A good NPN transistor will read OPEN. 5. Leave the black meter lead on the _base_ and move the red lead to the collector. The reading should be the same as in step 4. 6. Place one meter lead on the collector, the other on the emitter. The meter should read OPEN. Reverse your meter
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Maybe this will help. The large transistors you mention are probably not the problem. More likely you have a problem somewhere else. A common problem here is fractured solder joints on the connector pins. UNDERSTANDING DIODES AND TRANSISTORS By Randy Fromm Do you remember when you first started working on games? Remember when you didn't even know what a transistor was, let alone how to test one to see if it was good or bad? Now that you've been working on power supplies and monitors for a while, you probably can't recall a time when you didn't know how to test transistors and obtain substitute components. If you can call to mind the difficulty of those early days, you'll understand why I occasionally take a step back and take a look at some of the fundamentals of troubleshooting. Of these basic skills and procedures,  none is more important than the ability to test transistors. If you are already familiar with transistors, this discussion will probably be a complete bore. Consider yourself fortunate to possess such a vital skill and move on in the magazine. I'll catch you next month. Still here? That's good because you just gotta learn how to test transistors. It's really the whole basis for troubleshooting monitors, power supplies, redemption games, jukebox amplifiers and a host of other things electronic. The basic philosophy is simple. Since many circuit faults are caused by transistor failure, we don't always have to know exactly how the circuit works in order to repair it. All we have to do is test the transistors in the circuit and replace the ones that are bad. Since transistors all test the same (with a few exceptions) once you've mastered the test you can fix just about anything! Diodes We use the diode test function of the meter to test both transistors and diodes. Let's take a quick look at diodes first. The diode is the simplest semiconductor that we have. The schematic symbol looks like an arrow with a bar at one end. The arrow symbol makes a lot of sense since a diode is a one way gate for the flow of electric current. It's kind of like the turnstile at a supermarket or amusement park where people are allowed to move through the gate in one direction only. A diode has just two component leads. They're called the anode and the cathode. It's interesting to note how the diode actually works inside. Just about all of the diodes we use in games are made of an element called silicon. In its pure form, silicon is an insulator. It cannot pass any electric current through itself. During the manufacturing process, small quantities of impurities called dopants are added to the silicon. The addition of the dopants cause a change in the structure of the silicon atoms. When phosphorus is added to the silicon crystal, extra electrons are added to the silicon. This gives the silicon a net negative charge, with some free electrons scooting around inside the crystal. We call this type N silicon; N for negative. When boron is added to the silicon, it develops a net positive charge. We call this type P silicon. We can think of type P silicon as having atoms with holes in the electron shell, just waiting for an electron to fall into it. In fact, we call these atoms in the type P silicon holes. The diode is made from a single chip of silicon. One half of the chip is type P silicon; the other half is type N silicon. Where the two types of silicon come together, we have something called the PN junction. The PN junction acts as a kind of barrier to prevent the free electrons in the type N silicon from reaching the holes in the type P silicon. When we test diodes and transistors, we will actually use the meter to test this PN junction. Your ability to test this PN junction will enable you to repair more electronic equipment than any other single test you will perform!! It takes a certain amount of voltage to push aside the PN junction and allow current to flow through the diode. It takes an average of .7 volt to break down the PN junction and allow current to flow. Let's hook up this diode and see how it works. The anode is connected to the positive side of the battery. The cathode is connected to the negative side of the battery through the lamp. The electrons are repelled by the negative side of the battery toward the junction and the holes are repelled by the positive side of the battery toward the junction. Where they meet at the junction, the electrons fall into the holes. This pushes the PN junction aside and current flows through the diode. If the battery is reversed, the holes and electrons are attracted to opposite ends leaving pure silicon as an insulator between them. The silicon insulator prevents current from flowing through the diode. This is why it is called a semiconductor. Sometimes it conducts; sometimes it doesn't. It takes around .7 volt to break the barrier at the PN junction. This .7 volt is used up inside the diode as the energy required to push the current across the PN junction. We call this .7 volt the JUNCTION DROP. A normally operating silicon diode will have a JUNCTION DROP of between . 45 and .9 volt when measured with most digital multimeters. Most engineers and technicians use the average of .7 volt when discussing the JUNCTION DROP. Generally speaking, the larger the device, the lower the JUNCTION DROP will be. We can test this JUNCTION DROP with our meter. There is a special setting on the meter called the diode test. When we use the diode test, we are actually measuring the voltage required to get through the PN junction. What we should see is a normal JUNCTION DROP with the red lead on the anode and the black lead on cathode (diode conducting) and OPEN when the leads are reversed. This means that the diode is doing its job as a one way gate for current. When we read a normal JUNCTION DROP it means that current is flowing through the diode. When we read OPEN, the diode is blocking the current. It's obvious when a diode is bad. If we get a reading in both directions,  the diode is shorted. In fact, most diodes short when they fail. I'd say that 99 out of 100 diode failures are short circuits. If the meter shows OPEN in both directions, the diode is open. You can usually tell if a diode is good or bad, even when testing diodes in-circuit. Needless to say, if you test a diode in-circuit and it appears to be bad, you should test it again after removing it from the circuit just to be sure. Diode Specifications A diode is rated by voltage and current. The voltage rating of a diode is the maximum amount of voltage that the diode can block without breaking down. The voltage rating is listed as PRV (peak reverse voltage) or PIV (peak inverse voltage.) The current rating is the maximum amount of current that the diode can safely pass without getting too hot. Believe it or not, we use the letter I to represent current. Huh??? Early experimenters thought of current as intensity, so the letter designation I has remained with us. Io means output current. When substituting diodes, you can always use a diode with a higher voltage and/or current rating. Remember, the voltage rating of a diode has nothing to do with the voltage the diode is putting out. It is simply a rating of the maximum voltage that the diode can block. You can replace a 50 volt, 1 amp diode with a 400 volt, 1 amp diode. You could also use a 50 volt, 3 amp diode or even a 400 volt, 3 amp diode as a replacement. Transistors Transistors come in a lot of different shapes and sizes. The packages we commonly see in games are TO-3, TO-220, TO-218 and TO-92. There are two general types of transistors: NPN and PNP. Both are named for the way they are made. They're kind of like a sandwich with type N and type P silicon. The schematic symbol for the two types of transistors is basically the same. Notice that the arrow points away to designate an NPN transistor while the arrowhead points toward the center of the schematic symbol for PNP. Since we're talking a lot about P's and N's here, chances are pretty good we're talking about a PN junction somewhere. In fact, each transistor has two junctions. The NPN transistor is made of a single chip of silicon that has one area made of type N material, a thinner region made of type P silicon, and another N region on the other side. The PNP transistor has N silicon in the middle, surrounded by P silicon. A transistor has three leads and each lead has a name. They are the emitter, _base_, and collector. There are two PN junctions in the transistor that we have to test . One is between the _base_ and the emitter.  The other is between the _base_ and collector. It is the same test we used for the diode but we'll check two junctions instead of just one. TESTING TRANSISTORS Regardless of what type of package they're in, transistors will pretty much all test the same way. You'll need a digital multimeter with a diode test. 1. Set your meter to the diode test. 2. Connect the red meter lead to the _base_ of the transistor. Connect the black meter lead to the emitter. A good NPN transistor will read a JUNCTION DROP voltage of between .45v and .9v. A good PNP transistor will read OPEN. 3. Leave the red meter lead on the _base_ and move the black lead to the collector. The reading should be the same as in step 2. 4. Reverse the meter leads in your hands and repeat the test. This time, connect the black meter lead to the _base_ of the transistor. Connect the red meter lead to the emitter. A good PNP transistor will read a JUNCTION DROP voltage of between .45v and .9v. A good NPN transistor will read OPEN. 5. Leave the black meter lead on the _base_ and move the red lead to the collector. The reading should be the same as in step 4. 6. Place one meter lead on the collector, the other on the emitter. The meter should read OPEN. Reverse your meter
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