Quite regularly on every occasion electronic gadget don’t feature or work, we would right away suspect a faulty switch mode power deliver. But do you recognize that faulty or shorted components within the motherboard or important board may want to cause the power supply to forestall operating too?
Switch mode power supply (SMPS) are designed so successfully that every time there may be any quick circuit occur in the principal board the energy deliver would close itself off and totally stop operating. If you have no enjoy about troubleshooting transfer mode strength supply, you may think that the strength supply have problem in which in truth the primary board is the real purpose of no power hassle.
Switch mode strength deliver have a present dps-300ab-72a day feel circuit (in case you study UC3842 PWM IC pin 3, it stated I-sense which suggest current experience) and if there is brief circuit in the secondary side (either in secondary diodes or essential board), the present day drawn would be increase and this may lead the PWM IC to forestall producing output to the strength fet and thus the strength supply would close down. All this take place in a break up of seconds and you do not have the danger to understand if there are output voltages at the secondary side.
Some older layout of SMPS electricity supply do no longer use the PWM IC, but it do have the circuit to discover over modern-day drawn and close itself down on every occasion it detects a shorted component within the secondary aspect. One proper instance became the electricity supply utilized in printer. Printers generally have two boards; one was the electricity supply at the same time as the opposite became primary board. If there may be any brief circuit within the major board, the energy deliver could no longer work. In order to isolate at where the hassle is, one must remove the connector from the strength deliver board. Once the supply connector to the principle board was removed, you may now activate the printer and take a look at if there’s any voltages gift at the electricity deliver connector.
If there are 0 voltages measured throughout all of the supply (VCC) pins then we can finish that the strength deliver have problem and you could positioned your entire attention in this energy deliver board. What if there are voltages measured across the connector? This means that the primary board is causing the no power hassle maximum possibly because of a few shorted additives inside the essential board.
For your records, dot-matrix printers normally required voltages to feature. One is the 5 Volts (for good judgment IC, eeprom and CPU) and the other is 30+ volts for the vehicles. The query now is how can we recognise if the main board is the principle purpose that shutting down the energy deliver? Very easy, simply use your analog multimeter set to X 1 Ohm and measure among the supply pin (say five volts pin) and the main board floor after which opposite the probes. A good board ought to no longer show comparable analyzing and if you get two comparable ohms reading then because of this the 5 volts line had shorted to floor via a few defective components.
If you’ve got showed that the five volts line have trouble then how do we discover the perpetrator considering the fact that there are such a lot of components related to this line? TTL IC’s, CPU, EEPROM, transistors, diodes or even small filter out capacitors are all related to the five volts line. Either the sort of additives shorted ought to motive no electricity to the printer. You may additionally take away every components lead (5 volt supply) inside the primary board and hope that the short circuit could be gone. Assuming in case you manifest to get rid of one of the filter out capacitor pin and the quick circuit is long gone then we are able to say that the real wrongdoer is the clear out capacitor.
The actual trouble is what if the board has many additives on it and this can consume masses of it slow to isolate the problem with the aid of disposing of one pin at a time. It is not clean to pick out the deliver 5 volts pin to a spider IC that has 100 pins or more. Many spider IC’s have more than one 5 volts supply pin. Some even have four and some have 6 to eight supply pins. Does this suggest you have to check one pin at a time until you subsequently locate the fault? Not most effective that, to do away with the deliver pin from the spider IC’s and check for any brief circuit among the grounds required a excellent talent too. If you messed out the circuit board tune, the primary board can then be taken into consideration past repair. Even though you may repair the broken circuit tune, this doesn’t suggest you have solved the actual fault!
Do you spot the greater hassle stand up while you try to discover the fault? There should be some higher manner to tackle this sort of trouble. Yes it’s miles proper that you can use ESR meter to slowly music to the supply of the short circuit You can make use of the ESR meter to find quick-circuits on digital boards via checking the actual music resistance. One probe connects to the floor and the other to the circuit line and if the measurement rises as you probe similarly along the song, you recognize that you are heading to the incorrect course! If the ESR value decreases as you move along the tune then you are in the proper path. The hassle is what if the main board has double layers, 4 or even 8 layers? You may be losing lots of your precious time trying to music to the actual fault using the ESR meter technique! After explaining a lot about the problems, now’s the time that you are waiting for to get the answer on a way to clear up this form of fault speedy.
Do you realize that the DC regulated power deliver besides the use of it to strength up digital circuit it may additionally be use to troubleshoot and discover a shorted issue in a motherboard? Assuming you have got showed that the VCC deliver traces shorted to ground via some defective components, you may without problems hit upon it with the use of a variable virtual DC regulated energy supply. If you do not have the virtual one you could constantly use one with the analog panel meter that is cheaper.
Now connect the alligator clip from the positive output deliver to the five volts VCC pin inside the principal board and the bad output to the main board ground as shown from the picture. Once everything turned into achieved, it’s time to interchange on the dc regulated electricity supply. Slowly vary the knob clockwise and see the voltage growth. At the identical time the modern draw may be seen from the current digital meter readout. From experienced, if there’s a short circuit inside the fundamental board, on every occasion the voltage is growth, the present day will rise dramatically and if no quick circuit there would be less contemporary draw.
Okay returned to this problem, if you study that the current drawn additionally boom (hastily) as percentage to the upward push in voltage setting, you are now for sure that there may be aspect shorted inside the primary board. What does this imply? It is a good news to us, due to the fact if the present day drawn too much we will know the perpetrator by using touching at the freshest additives within the major board. Using your finger you could contact on any components which might be very hot. Touch at the IC’s, diodes, transistors, capacitors and etc. Once you positioned that best one aspect that is extraordinarily hot to the touch then that was the offender! That’s the real purpose which you are attempting to find! I’ve used this method to solved masses of fundamental board problem and commonly the culprit became out to be a faulty gate array and ram IC.
Why don’t I immediately turn the output voltage from the dc regulated power deliver to five volts since the defective essential board is also the usage of five volts to run? If I try this and if the faulty additives grew to become hot too fast, I’m afraid this may lead the defective element to open circuit. If the faulty factor open circuit, the modern draw will drop and the only clue that you have to pick out the perpetrator has been destroyed! If this aspect occurs then you can not have a higher rate to restore the board. Of direction you continue to can through changing one after the other the SMD spider IC’s but this could virtually eat up plenty of your restore time.
The above method I’ve just stated isn’t always limited most effective to printer main board; it can practice to other type of board as properly like the pc motherboard, hard disk, dvd, vcd, industrial board and and so forth. Get a DC regulated power supply and I’m sure you can stumble on shorted factor in the fundamental board within the shortest time viable! By the manner the specification of the DC regulated strength supply that I’m the use of turned into 5A 30 volts (variable kind). Have a very good day my friend!
