Hp Laserjet 4 Plus Power Problem

This old laser jet came in with no power symptom. It is relatively easy to repair the power module of this hp laserjet 4 plus model because most of the time is the electrolytic capacitors that have leaked which cause no power. The electrolyte that leaked caused surrounding components to become defective. Other models of this series of hp laserjet also having the same problem which is electrolytic capacitor leaked! The primary section power ic is very robust and seldom breakdown. The first thing that you need to do is to remove all electrolytic capacitor that leaked and clean the area with thinner solution. The smell generated by the electrolyte is really smelly and you need to clean the affected area fast. Then you can begin to check the surrounding components. In my case, i've found two 100 microfarad 25 volt capacitor has leaked, one C1815 transistor shorted between the collector and emitter leg and a 100 ohm resistor turned into high ohms. Other area looks clean and found no electrolytic capacitor to be defective with my esr meter. All the defective components that i mentioned above is located at the secondary power side.

I would like to mention here is that sometimes a leaked capacitor can measure good with an esr meter. Why? Because the electrolyte that came out from the capacitor haven't reach till the critical level yet that's why it still check ok with any of your esr meter. You have to take note on this. Anyway if you see any leaked capacitor just direct replace it regardless whether it check ok or not using your esr meter! Some equipment still function properly even the capacitor is already start leaking. If you didn't replace it somehow one day when the level of the electrolyte drop to below the average level your equipment might show intermittent problem or totally not working at all. The worst part is the electrolyte might affect the surrounding components and cause the part number could not be seen. If this happen the chances for us to successfully repair the equipment is very slim.
The above two capacitors that have leaked have a temperature rating of 105 C. If you observe the monitor mainboard generally they are using the 85C because the ventilation in monitor is better than laserjet. The laserjet power module is totally sealed with screws and it became hot and i believe the hot environment cause the electrolytic capacitor to leak after such a long time.
Troubleshooting the laserjet power supply is not much different compare to monitor. When your basic electronics knowledge is strong generally you can repair most of the electronic problems.