Repair of computer electronics power supply, part2
If there are serious suspicions about the power supply, I recommend that it be removed completely and disconnect all the wires coming from it to the computer blocks. To turn on the idle, I close the green and black (com & ps-on), while it should be twisted by a fan that is inside its casing and begin to apply voltages, we are primarily interested in 5 and 12 volts, but it does not hurt and check 3.3 . Be careful, the faulty unit may catch fire or explode! If within two to five minutes everything is working properly, you can measure the stresses under load as I described on the website http://electronicsrepair.site/. By the way, if the unit does not turn on at all, then we are most likely dealing with a burnt out fuse, but not the fact that its replacement will fix the computer’s power supply. It is necessary to ring the diode bridge on the computer power supply board:
You can find it further on the circuit after the fuse on the computer power supply circuit board. Naturally, all work with the power supply in the disassembled state must be performed only in the condition of 220 V AC disconnected from the mains! The verification procedure is as follows:
The tester is in the diode continuity mode, the diode icon should be near the digit of the measurement limit. Make sure that the circuit works by closing the probes and hearing the sound signal if the tester supports it or seeing 0 on the display. Then touch the minus terminal of the bridge with one probe and the other with alternating current icons, alternately, then swap the probes, in one case it should show a small resistance ohm 300-600 in the other should remain in the same state as with the open probes.
This procedure is repeated the same way for a positive conclusion. By connecting one probe to the positive terminal, and the other we touch the alternating pin alternately. A short circuit, that is, a resistance close to zero, indicates a breakdown of the bridge, a non-ring in both directions indicates a break in the diode. If you close the probes with both variables and get a zero or a squeak, then the diode bridge must be replaced.
It is better to carry out such manipulations with a diode bridge, there may be a short circuit further down the power circuit, but you can call it on the board first. Repair of the computer power supply unit costs it in particular with minimal components cheaper than the cost of the new unit, so it basically makes sense if you contact a computer repairman. In a normal service center for repairing computers to repair a computer power supply unit, the price should not exceed 1200-1300, otherwise it is not advisable.
As Cincinnati service center practice shows, basically the repair of the computer power supply by the hands consists in replacement of the swelled electrolytic capacitors on the power supply board, check just in case for those and the motherboard itself.
capacitors choose at the nominal and operating voltage exactly the same as you had originally, for the benefit of these are fairly common parts that you can get on the nearest radio market or order from the same China (the first option is better). Do not also change all the electrolytic capacitors in a row, then what you plan to put on a replacement may be worse in quality than factory ones. Generally speaking, containers are checked by special devices, but instead of them one can also use a multimeter in the resistance test mode.