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Looking to purchase an IBM 5291 terminal motherboard or base unit

That item is rare enough that any working motherboards you may find will probably be installed in their systems. I would highly suggest attempting to find what is wrong with the board and fixing it instead of replacing it. There are others here who would definitely know how to diagnose that board. These are rare enough that they are worth fixing.
 
HKG said:
That item is rare enough that any working motherboards you may find will probably be installed in their systems. I would highly suggest attempting to find what is wrong with the board and fixing it instead of replacing it. There are others here who would definitely know how to diagnose that board. These are rare enough that they are worth fixing.
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The problem about fixing this board is that all the TTL chips have IBM part numbers in place of the real types, and this is undocumented.
Service manual for the terminal don't say anything about fixing in case of failurs "replace motherboard", so believe that fixing it could be very hard or next to impossible.
 
To do something interesting while I got to fix the terminal and considering that may that will never happen.
Checked the specs from the manual about the display and can say it is in spec to an MDA monitor.
To build a small PCB that isolates the video signals that go to the display and only connects the power lines, this board can be removed and the terminal restored to its original shape with no permanent mod.
Using a couple of resistors and a diode to manage to get the intensity pin working from the Hercules input is not perfect, can't get the "flickering" attribute to display but most stuff looks great.



 
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