does any one show me the technique to diagnois a breakdown motherboard with a ocilliscope?

I seriously doubt that using an oscilloscope is a viable way to diagnose a motherboard. There are too many signals, and they're at too high a frequency. You need at least a logic analyzer.

There has been times I knew man that repaired motherboards this way although they had it combined with special test software. Some of them were very good, wrote that software themselves. But the economical repairtime decreased rapidly and the men had to swap boards. Most of them disappeared in short time. But the light still seems to be on as the last man forgot to switch it off.

Meanwhile motherbords became less crowded but the remaining chips have tens to hundreds of very small pins. A man that can replace such a chip, assuming you can get it, is more expensive in time then the whole boards value. Personnally I diagnosed boards down to the failing function only to find out that the required parts were custom made and nowhere for sale. Some were simple. A failing printer port for instance. This traces ended up in a big flat chip end I could see the signal failure on the o'scope. The port was unrepairable, but the damage could be circumvented by inserting a (printerport) card in an empty slot. A defective DMA-controller cannot be circumvented this way and the board was total loss.

So far my little history lecture. But the message will be clear: Even if you can diagnose a board to chip level, it's unlikely you can repair it let alone you can do so economically.

petrus bitbyter

the master motherboard repair gether quite a number of motherboard for parts replacement.

he uses 20 mhz ocilliscope. I pay him to repair my client's motherboard.