Electronics > Repair
What more i can do?
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222Lab_Test222:

--- Quote from: Harry_22 on December 12, 2024, 07:34:49 pm ---Data from EPROM IC16 is loaded with an error despite the fact that all incoming signals are correct.

--- End quote ---
Shall i check for EPROM IC15, for further observations. The same things we did with the IC16?
222Lab_Test222:

--- Quote from: CaptDon on December 11, 2024, 03:24:00 pm ---You almost need to write a simple loop program and burn it to an eprom and use it to examine what the busses are trying to do.

--- End quote ---
What type of program you suggest?
amyk:
Reading this long thread is very satisfying, like a mystery novel. :)
If I had more time I'd try to help out, but for now I'll just leave this one observation:

--- Quote from: fzabkar on November 19, 2024, 09:54:55 pm ---The scope traces suggest that the beeping stops as soon as Reset is released. This in turn suggests that this is happening well before BIOS starts executing. However, the OP has reported that the beeping continues on a good motherboard if the EPROMs are not present. This would suggest that BIOS code is switching off the beeping. I don't get it. :-?

--- End quote ---
If the EPROMS are not present the data buses may float high and feed the CPU FF bytes, and FF FF is not a valid instruction, causing it to triple-fault and reset repeatedly.
m k:

--- Quote from: 222Lab_Test222 on December 13, 2024, 04:41:30 am ---
--- Quote from: Harry_22 on December 12, 2024, 07:34:49 pm ---Data from EPROM IC16 is loaded with an error despite the fact that all incoming signals are correct.

--- End quote ---
Shall i check for EPROM IC15, for further observations. The same things we did with the IC16?

--- End quote ---

For doubled data an unchanging A0 is a good candidate.
But that requires that chips are one after the other.

Swap ROM chips and do address and data line scopes again.
Result for doubled data is E9E9 F8F8 ...
222Lab_Test222:

--- Quote from: m k on December 13, 2024, 06:10:34 am ---
--- Quote from: 222Lab_Test222 on December 13, 2024, 04:41:30 am ---
--- Quote from: Harry_22 on December 12, 2024, 07:34:49 pm ---Data from EPROM IC16 is loaded with an error despite the fact that all incoming signals are correct.

--- End quote ---
Shall i check for EPROM IC15, for further observations. The same things we did with the IC16?

--- End quote ---

For doubled data an unchanging A0 is a good candidate.
But that requires that chips are one after the other.

Swap ROM chips and do address and data line scopes again.
Result for doubled data is E9E9 F8F8 ...

--- End quote ---

ROM Chips means, Swap EPROM High and Low and watch signals on both?
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