I need an helb but.........

The first thing to do is verify that the 5 V and 3 V lines have the correct voltage. This can be done with a multimeter. The next thing would be to check for noise on these lines, but that will require an oscilloscope.

-- sam | Sci.Electronics.Repair FAQ:

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Thank you for your answer. I already checked voltages and them are ok. I know i need an oscilloscope. Considering the IC and its switching frequencies, what kind of oscilloscope do i need? Is a "20 Mhz band" enough? And what is the procedute to test the circuit with the oscilloscope? Thank you for your patience. Slang

Maybe start by describing what problems you are seeing with the CPU, etc.

As far as scope bandwidth, it's going to depend on what you're looking for. A 20 MHz scope won't be much use in looking at 100 MHz busses. But if you're just looking for noise on the power lines, it may suffice.

But, realistically, trying to give you a crash course in complex digital system troubleshooting, is not something that's likely to be very effective via a forum such as this.

-- sam | Sci.Electronics.Repair FAQ:

Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs.