Electronics > Repair
What more i can do?
Harry_22:
We just have corrected a human error made during diagnosis.
Actually, we didn’t notice the small needle pulse on the oscilloscope screen.
Conclusion for the future - it is necessary to observe the signal at different sweep durations.
In general, the situation is as follows. BIOS upload starts on the faulty board and continues for 12.5 µs.
The green LED probably indicates some important process - for example, data loading. OP found that his behavior changes from time to time. This means that the process is unstable.
That is, during the loading process an error inevitably occurs, but not always in the same place.
You can try to confirm this by observing any of the CE, OE, Address or Data signals.
Attached are explanatory drawings. I tried to make them intuitive.
Harry_22:
--- Quote from: SeanB on October 31, 2024, 12:26:21 pm ---I would suspect the 74ACT08 Ic IC7, and C10, as those are the most likely thing to fail, and then RTC does not update, which is detected by the BIOS.
--- End quote ---
Recently I had the situation where a chip that had been attached to a battery for a couple of decades deteriorated.
In our case, the clock crystal is suspended directly from IC23 RTC without any logic between.
This node with battery also haunts me. Multiple manifestations of an apparently similar malfunction could very likely belong to it.
Especially in light of new circumstances when BIOS tries to boot.
Poroit:
G'day All,
Please correct me if I am wrong...but I assume the BIOS is on the Flash Memory.
Are you convinced that the BIOS on the Faulty Board is not corrupt?
BTW
I see that 2nd Hand Underground Sewer Boring Machines range from $100,000 to $600,000 USD !!
I can see why the OP wants to fix it.
fzabkar:
The BIOS was tested on a working board. In any case, the OP is waiting for a chip programmer. Hopefully a dump will tell us something.
Harry_22:
--- Quote from: Poroit on November 23, 2024, 03:57:51 am ---
BTW
I see that 2nd Hand Underground Sewer Boring Machines range from $100,000 to $600,000 USD !!
I can see why the OP wants to fix it.
--- End quote ---
Hello colleagues!
Yes, BIOS in EPROM.
Now it’s clear why OP was afraid to disassemble the working board.
I always preferred not to know the price of the equipment being repaired.
You see, this just gets in the way!
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