pc motherboard with inductor problem

thanks i notice it also reads the components in series which is also very handy its a very nice meter it narrows down things very fast ihad it in a board a while ago and i got too high capacitance but i have a feeling its just taking from some were else in series

think this esr meter is really handy i have narrowed down to 6 mosfets there is 3 d types and 3 n types there is also 2 chips close to them also used to run the mosfets all 6 mosfets have the same code which is phb 55n03lta getting different readings from some of them what does the d and n in the right hand corner stand for i think one of these are throwing out to much voltage

insomnia said:

ok so i have this pc motherboard turn it on the fan spins for about 6 seconds the n cuts out so i was messing about seen a few swelled caps took them out replaced them but still have the same problem so i started checking the inductors by taking them out the last one i took out it had 6 coil turns on it after i took it out the board stays going with out shorting out now im thinking is the inductor or something on the trace of it why would it short out i know these store energy in magnetic field but cant picture whats going on

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After replacing several components I believe your troubleshooting methods have evolved into a "shotgun" technique. Visual inspection is a good start but since this is a PC motherboard there are a few logical steps you can take.

I agree with what Nigel said awhile back as to replace the board however it may be wise to eliminate the PSU being the problem. Then too, it seems to have become a good learning tool.

The instant the front panel push button is pressed a few things take place in quick order. Give this link a read to see what happens. Granted it covers the first 500 mSEC or so but it gives you an idea of what is going on.

Since you say the fans spin up and things happen for about 6 seconds you should have time to check the PSU voltages out. The top of this page shows the main motherboard connectors both the older 20 and new 24 pin connectors. Using a voltmeter you can probe the connector and see if the voltages come up and how they look. You have 12 volts, 5 volts and 3.3 volts to start with. They should all be close to nominal at +/- 5%. Note if they are steady.

Those ideas may help.

Ron

thanks ron and yes if it was a case of replacing the motherboard i would have done that this is for learning purposes now and thanks for understanding i love a challenge like this . i will now try what you said and see how it goes as have tested mosfets all good small smd transistors not 100% tested i was testing them with the multimeter in diode range and they seem to send voltages the ones i have tested another thing i was thinking about was i have put some new caps in were i was getting high esr no cap reading but got 1.14 on a 3300uf 6.3v but there is a few different make caps in there now but most seem to have low esr at this stage


this some cap readings that im thinking about

3300uf-6.3v esr reading 3212uf-0.02
2200uf-16v esr reading 1929uf-0.03
2200uf-16v esr reading 1956uf-0.03
2200uf-16v esr reading 1968uf 0.02