246
UF-5500 / 4500
13.4.
Main Board Section
When the unit fails to boot up the system, take the troubleshooting procedures very carefully. It may have a serious problem.
The symptom: No response when the power is turned on. (No LCD display, and keys are not accepted.)
The first step is to check the power source. If there is no problem with the power supply unit, the problem may lie in the digital
unit (main board).
As there are many potential causes in this case (ASIC, DRAM, etc.), it may be difficult to specify what you should check first. If
a mistake is made in the order of checks, a normal part may be determined faulty, wasting both time and money.
Although the tendency is to regard the problem as a serious one (IC malfunction, etc.), usually most cases are caused by solder
faults (poor contact due to a tunnel in the solder, signal short circuit due to solder waste).
Note:
1. Electrical continuity may have existed at the factory check, but a faulty contact occurred as a result of vibration, etc., during
transport.
2. Solder waste remaining on the board may get caught under the IC during transport, causing a short circuit.
Before we begin mass production, several hundred trial units are produced at the plant, various tests are applied and any mal-
functions are analyzed. (In past experiences, digital IC (especially, DRAM and ROM) malfunctions are extremely rare after
installation in the product.)
This may be repaired by replacing the IC, (DRAM etc.). However, the real cause may not have been an IC malfunction but a sol-
dering fault instead.
Soldering faults difficult to detect with the naked eye are common, particularly for ASIC and RA (Resistor Array). But if you have
an oscilloscope, you can easily determine the problem site or IC malfunction by checking the main signal lines.
Even if you don’t have such a measuring instrument, by checking each main signal line and resoldering it, in many cases the
problem will be resolved.
An explanation of the main signals (for booting up the unit) is presented below.
What are the main signals for booting up the unit?
Please refer to
The ASIC (IC300) controls all the other digital ICs. When the power is turned on, the ASIC retrieves the operation code stored in
the ROM (IC402), then follows the instructions for controlling each IC. All ICs have some inner registers that are assigned to a
certain address.
It is the address bus by which the ASIC designates the location inside each IC. And the data bus reads or writes the data in
order to transmit the instructions from the ASIC to the ICs.
These signal lines are all controlled by voltages of 3.3V (H) or 0V (L).
Don't replace ICs or stop repairing until checking the signal lines.
An IC malfunction rarely occurs. (By understanding the necessary signals for booting up the unit, the "Not Boot
up" display is not a serious problem.)
Содержание UF-4500
Страница 180: ...180 UF 5500 4500 ...
Страница 248: ...248 UF 5500 4500 13 5 Test Chart 13 5 1 ITU T No 1 Test Chart ...
Страница 249: ...249 UF 5500 4500 13 5 2 ITU T No 2 Test Chart ...
Страница 281: ...281 UF 5500 4500 10 10 11 15 12 17 18 19 20 21 22 23 24 28 29 30 27 25 26 21 13 14 16 30 ...
Страница 287: ...287 UF 5500 4500 130 131 132 133 134 135 136 137 138 139 140 141 PCB2 A UF 5500 only CN1 ...
Страница 289: ...289 UF 5500 4500 PCB8 PCB4 160 161 163 162 164 167 168 171 177 178 172 173 174 173 176 169 170 162 164 A A 165 ...
Страница 297: ...297 UF 5500 4500 ...
Страница 305: ...305 UF 5500 4500 ...
Страница 309: ...309 UF 5500 4500 A1 A3 A4 A6 A7 A8 A9 A10 P1 P2 P3 P4 P5 P6 P7 P8 P7 Drum Cartridge Toner Cartridge P9 A11 ...
Страница 311: ...311 UF 5500 4500 501 502 503 504 506 507 505 508 509 511 510 514 513 512 P51 P53 P54 A51 P52 ...
Страница 362: ...362 UF 5500 4500 ...
Страница 365: ...365 UF 5500 4500 Published in Japan ...