大型游戏机原理与rma引起的故障维修方法（Troubleshooting method and principle RMA large game machine caused by）

大型游戏机原理与rma引起的故障维修方法（Troubleshooting method and principle RMA large game machine caused by） 大型游戏机原理与rma引起的故障维修方法(Troubleshooting method and principle RMA large game machine caused by) Troubleshooting method and principle RMA large game machine caused by Hua Shuo electronic technology / 2010-03-11 The computer board core is composed of CPU, RAM and ROM and the buffer, seen from the operation with MC68000 is directly related to the WORK RAM, which is two pieces of 62256, computer crashes and plate fixed plate is mainly due to its damage. Most of the machine RAM is socket installation, can conveniently use the replacement method, the specific example shows. [cases of 1] type: the dragon, dragon, street fighter canon. Fault phenomenon: frequent random crashes. Check and repair: failure to address this, we may try to replace the RAM monitoring, basic work, in any case where the random fault, no matter what the board can try. [2]'s plate type: Fault phenomenon: Crash Check and repair: on observation of transient waveform, each boot was found high 8 bit data line 68000 at the moment of starting jump in state waveform, using scissors cut off foot isolation method, found a buffer of 74LS245, it will be broken foot after the board starts. After the replacement operations are normal start. [cases of 3] type: Ninja spirit Fault phenomenon: Crash Check and repair: boot reset and clock normal measurement, a transient waveform observation of bus driver low 8 data line damage investigation is a 74LS245 on the interface. According to the high potential low 8 bit data bus in abeyance, the judge may be 74LS245 pin power short circuit phenomenon. In case of power failure, the power supply connecting 5V with digital table at one end, the other end of the 74LS245 foot, in the non power pin is shorted to generate cracks. This fault is 74LS245 third feet and a power of internal short circuit host operating port. You can change. [4]: millionaire plate plate Fault phenomenon: the board can start, but can not run, the foreground is broken. Check and repair: measurement data bus has a present state, using line checker to find along the line connected with the chip, check to a 74LS245 (U34) bad performance, after the replacement of normal. [cases of 5] plate: Wolf of the battlefield Fault phenomenon: poweronselftest normal, can automatic demonstration, once the operation has crashed, the image is light. Check and repair: through 3 cases turned Ninja maintenance, can know I/O 74LS245 even if not in the circuit can also start and automatic presentation. There is a direct relationship between the analysis of crash and interface operation in this case is caused by interface fault, 74LS245 fault, just chip damage different procedures, once the signal is transmitted to the ground bus side will cause a crash, because each press the start button will lead to crashes, along the line to check a 74LS245, after the replacement of all operations are normal. 6] type: 97 cases [star plate Fault phenomenon: don't start, no image. Check and repair: after electrifying touch, 74LS245 (U28) high temperature measurement, remove the bad judgment, after the replacement of normal. [example: South Korea Ming plate 7] plate Fault phenomenon: Crash Check and repair: the tensile load in the 68000, 17 pen hanging 18 feet high, the address line in its role is still no characteristic waveform, Check the monitoring part of the EPROM were normal. The high address check address sending device 74F74 is not normal, the pulse generator directly loaded in the input D 74F74 (2, 21), Q (5, 9 output end foot) waveform than in high state, abnormal, directly remove change after the entire plate normal. This is also an example of the address bus fault caused by the phenomenon of death. Note: maintenance, do not blindly, there must be a purpose to write, test pen full board Luantong do not use, do not use the test probe in IC even sweep the pin, it is very easy to cause the damage, such as: there are a lot of 74LS157 on the IC board. 74S158 is a 2 choose 1 data selector, source code output. 15 feet E is allowed to signal input, active low. Circuit design is usually ground, 16 feet is just another power. If the short circuit, 157 15 feet and 16 feet due to the short circuit current is very big, the printing plate will fine line is burnt in an instant, as this phenomenon is also 74LS161. The cause of this failure, if you have not noticed, then this board is difficult to repair, because some lines are left at the bottom of the IC line, is not observed, try not to short-circuit test, but in some places can also be short circuit, such as memory data line, D end and the Q end of the D trigger. It is worth noting that the common function of the chip, pin must bear in mind that a 74LS374D type flip-flop, OE terminal output allows "the rising edge of the clock effectively. D is the input, Q output, all D trigger is such. The 74 series has a lot of devices on the computer board commonly used, one-way, two-way, and three states. If these basic concepts are not clear, with the oscilloscope probe everywhere even detected fault, stabbed, also do not know it is bad. It is better to repair the board control of digital circuit and integrated circuit data part, with the use of oscilloscope. Any of a series of IC 74 are input, an integrated circuit output end and end condition. In the maintenance of the computer board, 74 series of damage rate is not the highest, but not luck, that it would not be bad, until now, the 74 series of all problems, there is certainly a ratio associated with it in the circuit of the task, working conditions and the working state of IC. The most bad is 74SL245, its working condition is a two-way high-speed three state, followed by the above 74LS244, 74LS04 interface and 74LS174 and 74LS74.