"Pooh Bear" wrote in message
...


DaveC wrote:

Thus spake William at MyBlueRoom:

http://www.csee.umbc.edu/~plusquel/3...8086_IO3.html\

looks like the 8279 has an internal OTP EPROM.

This is what I need help determining. If this is a "production
programmed"
device (burned at time of manufacture), it's a deal-killer for my
customer --
finding a programmed replacement is pretty much not going to happen.

It appears not to be.

http://www.csee.umbc.edu/~plusquel/3.../8086_IO3.html

Graham


It seems to me that everyone is "going off on one", before the OP has
applied at least basic proper fault finding techniques. Before going in
shotgun and replacing parts that - trust me - seldom if ever go faulty, you
should first check that the 5v supply is absolutely good - voltage, ripple
AND noise, that the reset generator is working correctly, and that most
importantly, the system clock generator is running, and producing a correct
amplitude and frequency, signal. Also that any following clock distribution
buffers are working.

If none of those checks turn up the problem, and in at least 80% of cases on
this old simple logic, they will, then the next move is to download a
datasheet for the display controller, and figure why it's not driving the
displays. The required inputs are not many, and not complex, and require
only a 'scope to verify.

From years of experience repairing electronic equipment, I can tell you that
blanket replacement of components in the fond hope of hitting the right one,
is about the worst approach that you can take, and likely to result in more
problems than the probably simple one that you had in the first place.

Arfa