For this time I don't deal with motherboards, but with problems related to some PCI sound cards, I have three of the same model, two are branded CREATIVE LABS MODEL:CT4810, the other only CT4810, I think they are basically the same board, but there are some differences, I take care of the two CREATIVE LABS branded cards for the moment, they look like twins but near the microphone jacks (pink), the C20 in one is electrolytic, in the other it is an SMD.
The main problem with these cards is that when it is inserted into the PCI slot, the PC does not start, that is, it does not start at all!
It looks like a short problem, and the power supply intervenes preventing it from starting, if we remove the sound board, the PC works without any problem!
First of all I checked if between the PINs of the comb (PCI), there was a problem between the ground PINs and those of the voltages (3.3V 5V 12V, and -12V), there is no -5V, but I think it is only used by ISA slots, however no short (surprise!), I thought I saw the continuity in a PIN!
In short, a little surprised (but not too much), I concentrate looking among the electrolytic capacitors, the values of some are a bit strange, but having been tested on board, it is possible that these values are influenced by other components on the circuit.
I start looking everywhere, apart from the 24.576 quartz, which I can't verify, I try the rest with the tester on diode test, I start to check everything I see except the resistors, because these allow a current passage, so even if in short they can't prevent the PC from starting, the capacitors instead, often connect to ground, so if it's short, it would explain why the PC doesn't start.
By now, I had tried to control practically everything, in reality I had left out a part that I thought could not be important, however today I tried to see if the inside of the jacks had a problem, and even there everything was normal, so now short of ideas, I try to check some SMD next to the microphone jack and LINE-IN, to make it short (!), I find three short SMD capacitors, it's C1 C2 and C3.
Today I won't be able to finish the job, because all three defective capacitors will have to be removed, from both boards, and then they will have to be replaced with others, unfortunately I don't know the original values, the C3 looks brown, while C1 and C2 are purple-gray, in short, I'll see if I can find other capacitors the same, on scrap motherboards.
It remains to be seen if replacing these SMDs will solve this startup problem, I guess so, but before welding the spare ones, I would also check the resistors next to it, in short, it seems that the resolution of the fault is possible, if I succeed I will have recovered a couple of PCI sound cards, the third card instead, I should examine it better, but I anticipate that the three SMD capacitors work, and so I have to look for another problem, I think I will have to start checking everything all over again.
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