Hitachi CTP-236 color Diantong boot without light, silent, listen carefully without any noise fault repair method machine |
| Time£º2014-07-28 10:08:27 Source£ºNetwork Author£ºUnknown Clicks£º1756 |
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F5vservice manual download site
F5vservice manual download site
In order to confirm the above judgment, disconnect, 54 v, 108 v power supply output load, with a 1 k Ω / 20 w resistor as dummy load in, 108 v power supply output, boot after the measured voltage also increases, it is completely confirmed that the fault is still in the switch power supply circuit, and is likely to be in regulated part. F5vservice manual download site
F5vservice manual download site
This machine is self-excited parallel horizontal frequency synchronization type switching power supply, can start, explain the oscillation circuit is normal. + l08V voltage rise, the estimate is caused abnormal pulse width adjusting circuit. The pulse width of switch power supply depends mainly on the RC charging time constant. The adjustment process is: when switching circuit output voltage rises, error control voltage is also rising, base of VT903 tube potential rise, collector current increases, equivalent to the c - e electrode resistance decreases. In this way, the switch tube VT901 conduction during C908A capacitance on the charging current is part of the VT903 tube to drain away, this is equivalent to the RC time constant decreases. VT901 exit the saturation state, therefore, can shorten the time needed for, thus reduce VT901 tube conduction time, narrow pulse width, the output voltage drops, achieve the goal of a stable output voltage; On the contrary, when switching circuit output voltage drop, the control process on the contrary, eventually make the output voltage rise. F5vservice manual download site
F5vservice manual download site
You can see from the above analysis, VT903 pipe here is essentially a shunt, the shunt volume size, determines the VT901 tube conduction time, thus controls the pulse width, achieve the goal of a stable output voltage. Because in the above checks, switching power supply didn't find other abnormal elements, estimation is VT903 tube has a problem on the new branch. In order to confirm this judgment, had to use a beta material around 189 authentic 2 just change to VT903 sc2060 tube replaced. After this change, electricity boot, + 108 v voltage return to normal, troubleshooting.
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