Besides using passive protection systems, today most television manufacturers have added an active protection system on its products. In passive protection system, its components are just a fuse (fuse) That will of burn (break) if the system is experiencing excessive flows, and / or zener diodes That Would short-circuit (short / konsleting / shorted) if the system is experiencing berlebihah stress. While on active protection system, the system will from go into PROTECT MODE marked with the plane is in standby mode and coupled with an indicator light That flashes with a particular rhythm (in Some brands) if the system detects That conditions are not normal.
Application of an active protection system is meant to protect the aircraft from more serious damage, protecting the damage to the CRT tube, preventing the Emergence of x-rays, and Prevent the possibility of burning of components to generate smoke cans That triggers an alarm active / fire sprinklers in places Nowhere implement fire prevention system with smoke detector (smoke detector).
The points of protection
Many of his points of protection on every television set brands vary, but from his many television brands in the market, Sharp has the highest record in terms of the number of points in protection, so do not be Surprised if a lot of Technicians found That Pls complain a brand sharp television repair, and not A Few others and then replace it with the engine (chassis) Just Because it was Difficult to fix it but Sometimes just due to the protection systems are not normal.
The points of protection Generally applied to a television set Including: x-ray protection, protection of 5 volts, 8 volts, 16 / 26 volt (Sound amp supply), 24 / 45 volt (vertical supply), 33 volt (BT tuner) , and 180 volts (RGB Amplifier), B +-current protection, protection of vertical deflection (vertical guard / CRT protector / neck protectors), protection ABL (automatic brightness limiter), over-temperature protection (over thermal protector) and white balance protection .
From many points of protection cans be grouped into 5 protection system, namely:
1. Absence of Voltage Protection System (No Voltage Protection / NVP)
Protection System is Used to protect from the absence of voltage on the point That the protection, why does not the voltage be on protection?, In the absence of voltage at a point Could Be the caused by a short circuit / konsleting at That point so as to Prevent power supply to the power supply at That point occurs excessive burden That cans result in power supply is even more serious damage to cans cause burning of components due konsleting.
Protection system is Also Used to protect the CRT tube damage the caused by the destruction of the vertical deflection system, whereby if the vertical deflection system problem causes a horiontal will from a very bright line on the CRT screen the which if left unchecked for long periods cause a will from phosphor coating on the CRT tube on fire, by therefore the protection system mounted on a vertical deflection is Sometimes Also Called the CRT neck protector or protector.
The way it works this protection system is as follows, note the series scheme, During normal conditions, the Greater the voltage on pin Protec is more or less equal voltage Vcc due to the R Pull Up, but at the time of an abnormal condition in the which the voltage at the protected point Lower Than the voltage on pin Protec, then the voltage will of flow through the diode protection and cause the voltage on pin Protec down by the voltage at the point of being protected, if the protected point of zero volts, The voltage on any pin Protec down to zero volts, in this condition, the protection system changed from active due to the IC pins Protec Micom / Jugle That Pls apply the system is active low (active low), note the pull-up resistors That Is Protec pin placed on showing the pin is active During conditions of low (active low).
But if there is a protected point higher voltage Than the voltage on pin Protec, then the voltage will from not flow through the diode protection, but protection diodes leak, so That if the active protection system, Pls the point to be protected under normal conditions, is His protection diode suspect Damaged, or pull up resistors That possibility open (resistance Increased / prolonged).
Protection system is usually applied for the protection of 5 volts, 8 volts, 16 / 26 volt (Sound amp), 24 / 45 volt (vertical supply), 33 volt (BT tuner), 180 volt (RGB Amplifier) and the Vertical Output (via a first rectifier).
2. System Over Voltage Protection (Over Voltage Protection / OVP)
Protection System is Used to protect from voltage spikes at the point to be protected so as to Prevent the components in a protected spot on fire due to excessive voltage, this protection system is usually applied to Prevent Also the CRT tube out x-rays or breaking Because of the coil heater the heater voltage is excessive.
This protection system will from work if the voltage at the point That the protection is higher Than the working voltage protection diode (zener diodes), Pls whereby the voltage on the protected point higher Than the working voltage protection diode, the voltage will of flow through the diode protection and cause the voltage on Protec pin-point increase is by the voltage on the protected reduced working voltage zener diode, in this condition then Becomes active protection systems Because of the nature of Protec pins That will of be active if there is a positive voltage at the input , note the pull down resistors on pins Protec showing the pin is active Pls conditions of high (active high).
But if at That point there is a protected Lower Than the working voltage protection diode voltage, the voltage will from not flow through the diode protection, but protection diodes leak, so That if the active protection system, Pls the point to be protected under normal conditions, His protection diode is suspect Damaged, or pull down resistors That possibility open (resistance Increased / prolonged).
The series above is Used if the pin on the IC Protec Micom / Jungle implement Active During conditions of high (active high), but if the pin on the IC Protec Micom / Jungle implement an active system on the condition of low (active low) , then added as an inverting transistor, Such skematiknya follows.
Over Voltage Pls ProtectionCara it works is the voltage at the point That the protection is higher Than the working voltage of zener diode D2, the voltage will of flow through D2 to the base of the transistor and causes the transistor is active (on), while the active transistor means feet on collector and emitter transistor short circuit occurs, so this is tantamount to a connecting leg D1 cathode to ground, Because D1 in pairs in reverse, then the voltage will of flow through D1 and cause the voltage on pin Protec Becomes zero volts, in this condition then Becomes active protection system.
But if on the point of lower voltage diprotek That there Than the working voltage of zener diode D2, the voltage will from not flow through the zener diode D2, so That the transistors in the inactive state (off), unless the zener diode D2 having any leakage , so the voltage will from Remain flowing into the base of the transistor to trigger the transistor to be active (on), or if the leaking transistor collector and emitter so That the legs are always short circuit at the base of the transistor even though there is' no tension at all, so if it turns out at the point to be protected but there is' normal stress protection system in an active condition, deserves the suspect or the D1 and D2 have a leak, TR experiencing leakage or short, or pull-up resistor That possibility open (resistance Increased / prolonged).
Protection system is usually applied to the heater voltage protection (through the rectifier and voltage divider circuit / voltage divider first), supply voltage of 8 volts and the ABL.
3. Flow Over Protection System (Over Current Protection / OCP)
Protection System is Used to protect the power supply current excessive burden cans That leads to Damaged power supply, the protection system is usually applied to high voltage supply (B +), or the vertical driver supply voltage.
In simple terms the workings of this protection system, cans be explained as follows:
When the abnormal load will of cause the current in R1 (IR) increases, say to 2 amps of normal current of 1 ampere, if R1 at 0:47 Ohm, the voltage across R1 (Vr) cans be computed as:
Vr = IR x R1
Vr = 2 x 0:47 = 0.94 volts
Potential difference of 0.94 volts at R1 Also the which means the potential difference, Between the base - emitter (VBE) will of cause TR1 TR1 changed from active (on) Because the voltage of 0.94 volts have exceeded the active voltage PNP transistors the which is only 0.6 volts. Because of TR1 is active, then there is a short circuit Between the emitter and collector of his legs, so That at the foot of collector voltage of TR1 Arise near its emitter voltage, Because voltage is fed to the base through R2, Causing TR2 TR2 was active (on), while the mean foot TR2 active collector and emitter of TR2 ensued short circuit, and is equivalent to connecting the cathode leg of D to the ground, Because the diodes in pairs in reverse, then the voltage will of flow through the diode and cause the voltage on pin Protec be at zero volts, on condition This then Becomes an active protection system.
However, if the load did not experience abnormal, then the current IR was in normal condition, say at 1 ampere, so the potential difference, Between the base - emitter TR1 at 00:47 volts only (obtained from IR x R = 0:47 x 1 = 0:47), Because it is still under stress PNP transistor active of the magnitude 0.6 volts, so TR1 in the inactive state (off), Because TR1 off, then on the basis there was no tension so TR2 TR2 was in. a state-of-offs, in this Same Condition D floating so let cathode protection system in conditions inactive, Because the pin Protec in supply by the pull-up resistor R3 to a voltage Vcc, so the voltage on the pin That Protec approximately at the voltage Vcc .
But if the protection system is active even though there is no proper abnormal load on suspected resistance value R1 or R3 is Increased (delay), the resistance of R2 is decreased, TR1 or TR2 leak or short, or it leaks Dl.
Protection system is usually applied to protect the supply voltage B + to the Travo Flyback supply voltage and the vertical driver.
4. Over Temperature Protection System (Over Thermal Protection / OTP)
Protection System is Used to protect the system from excessive temperatures, but this protection system is usually only found in power supply circuit is already integrated in the IC power supply is the which most type SMPS (switching mode power supply), in contrast with other protection systems That simply cause a plane to the standby mode if the protection system is active, the protection system of this OTP will from directly cause the death total for the aircraft power supply That earnest stop working if the protection system detects the temperature exceeds the limit.
5. Protection System White Balance (White Balance Protection / PLT)
Protection system is only found on the Sony brand television sets, and the effects if it is an active protection system different from other protection system, whereby if the system detects an error then this protection will from not cause the plane to standby mode let alone off, but earnest only cause Becomes dark picture. This protection system in the workings of detecting cathode current (IK) in the third cathode RGB on a CRT tube, the which is then fed to the input pin IK the which is available on his jungle IC.
Menon-Enable Protection System
Before you can do the tracking part the which suffered damage to the television set located in the protected conditions of course, We must first deactivate the protection system, Because if the protection system was active, We Can not possibly do the tracking of the Damaged Part Because The television will from go directly into the standby mode shortly after power on.
In the example Used in a television discussion marks SHARP 51U200 model, the which in this model there are 8 points of protection, to disable the entire protection cans be done by removing jumpers J718, J421 and J906, J718 the which connects with protection against voltage of 180 volts, heater, 8 volts, and the ABL.
While the J421 connects with protection to 26 volts the which is the voltage supply power amplifier, and J906 to the connect with the output protection vertical (vertical guard), 5 volts and X-ray protector (x-ray protection) is Actually Also connects with the heater but here Used to protect against excess voltage on the heater, cans Because x-rays Arise Also due to Increasing voltage on the heater.
After protection system disabled, it will from be known the which part is Damaged based on the existing symptoms, but the way it is harmful if the active protection system Because of konsleting, Because it cans cause one of the components would be burned as a result of konsleting , but how This is the fastest way to find damages based on the symptoms That Arise, the table below shows the symptoms That May Arise Pls a television set at the turn after the successful protection system disabled, the part That May be Damaged Nowhere and Nowhere That the components act as detectors of protection:
Symptoms That May be broken portion Detector Protection
Picture blanking RGB Amplifier hehilangan voltage 180 volt D613
Dark images, the heater does not turn on the CRT heater voltage loss D614
Dark picture, the OSD is not normal ABL Tension D606
Normal picture, no sound Pow amps 26 volt supply voltage loss D309
Figure striped horizontal vertical deflection is not normal D504
Images are too bright not normal ABL D606, D607, Q603
Picture Plain / hor die total loss system voltage Vcc 8 volt D608, D609
Standby / not Able to receive broadcasts losing 5 volts Systems D572
Another way to find out the Damaged section is solderan by disconnecting one leg of the entire detector protection, for example by removing the cathode of diode solderan foot-protection diode detector That Is D613, D614, D606, D309, D504, D607, D608, D609 and D572. After all the foot-diode detector diode cathode protection despite then turn on the television set, while the television sets turned on, then plug one by one leg using the tip of the AVO meter socket or screwdriver tip trim to the PCB track it, if Pls one leg cathode diode detector is in connecting with the PCB track her and found the television set to the protect mode (standby), so That part is Damaged, from here Further cans be tracking to find the Damaged components and then cans be repaired.
