Looking to replace the controllers on a couple of older keyboards. Mostly looking to address some layout issues in a permanent way so quite fine to continue using them under AT protocol with ps/2 cable. I would like to just be able to drop in a replacement into the existing 40pin socket and program it and be done. This will be my first attempt at doing this so I would favor a direct replacement as it seems it might be easier than some other options. What is the best way to go about it and what would be best parts to source?

So I see a fair number of views, but no response. So am I just asking something incredibly dumb and everyone is being polite? LOL. Or Did I just not make any sense? I suppose I could go with one of the usual suspects (teensy, chameleon, etc)... but I am really not sure of pros/cons of the different options. What is the easiest to work with for a first timer?
So what I want to accomplish is: need to remap some of the really awkward layout choices and add 2nd layer on mid 80's 84key. PCB also appears to have full support for backlight even though is was made in 1985/6 which I find pretty amazing. So I have been considering using that so having some support to turn light on/off at the least would be nice also.

First, you need to get a datasheet of the old controller to know its pin outs.
Then, Search pin compatible modern MCU in the market. I'd recommend Atmel AVR which has better support from Free Software community.
If you can't find pin-compatible MCU off the shelf you'll need to make a kind of adapter socket yourself.

Did search of what is printed on the chip, but only find places purporting to have them in stock, nothing useful looking.
It has "8626" "UM8049-8-523" and "DY-151" and a little globe logo that seems to have C and backwards E in it...
The traces on the pcb are huge and quite easy to follow. Bottom half of pins seem to go straight to switch matrix, while most of top goes to jumpers, diodes, resistors, crystal, capacitors. Maybe someone experienced can make sense of it and be able to advise better, I will get some pictures of it up.

If you can access the matrix directly there should be no big problems using a Teensy to interface it. It's also easy to use a Teensy to analyze the matrix layout. I have pictures of me doing it in this thread http://geekhack.org/index.php?topic=343 ... #msg640733 If I were on my computer I would have uploaded it directly here...

lysol wrote:It has "8626" "UM8049-8-523" and "DY-151" and a little globe logo that seems to have C and backwards E in it...

That sounds like an 8049 made in week 26 of 1986 by ... someone (possibly Cypress ?).

Same as bpiphany, I'd recomnmend replacing it with aTeensy. Just figure out which pins connect to the matrix (directly, and possibly indirectly through any multiplexers) and ignore the rest of the controller.

Here is the keyboard in question, show the topside so can see what is attached there besides the switches.
Do you guys see any major issues to be aware of?

Can't see any pitfalls at all!

The eight lines that go via the red resistor pack will be inputs to the CPU from the matrix, so the other 11 or so that go to the matrix will be outputs from the CPU to strobe the matrix. The strobe is active low.

Another three output lines go from the CPU to the 14-pin chip (presumably something like a 7407 hex buffer with open collector outputs) and from there to the LEDs. You could either use those buffers, or wire the LEDs more directly. If using the buffers you can just wire the Teensy's power pins to the 8049's power pins to get it powered up (which will also provide the +5V for the common side of the LED resistors R6, R7 and R8).

The resistor pack RP1 could be used or removed. If it is left in, +5V needs to be applied to its common pin.

I'd probably use the buffer and the resistor pack, just because it will be less work and keep the wiring neater!

Soarer wrote:

lysol wrote:It has "8626" "UM8049-8-523" and "DY-151" and a little globe logo that seems to have C and backwards E in it...

That sounds like an 8049 made in week 26 of 1986 by ... someone (possibly Cypress ?).

I looked it up for fun: United Microelectronics Corp

But indeed, it might be easier to replace it with a full Teensy and use existing keyboard firmware rather than trying to fit everything into a 8049 and suffer to get it to talk USB.

Well, as I said before I could care less about usb. Keeping it with ps/2 would also be quite fine to me. One of the things that made me want to avoid some other options initially was due to my case design. I intended to make it only just as big as the pcb/plate basically and as slim as possible with plexi. I am still not sure where or how I would mount something like a teensy since it can't go where the original controller is I don't think.
I've been doing some research, and is seems atmel 8051 flash based 40pin may be an option? Seems to be pin compatible with the existing controller.

I can well believe there's an 8051 variant that is pin compatible or close enough, which would make it feasible. The original 40 pin 8051 pinout isn't compatible though.

The big advantage of the Teensy (and USB) is ease of development and programming (as in, loading code onto the chip). Good, free, C compiler. Debug print output.

For mounting a Teensy you could probably line up some pins with the 8049 holes and use wires to link the rest. So it would almost be flush with the PCB. Maybe it could sit where the 8049 is now, or just behind it (roughly in a line with JP11). The thickest part would probably be the USB plug on whatever cable you plug into it.

Thanks for all of the info, even if I don't fully comprehend all of it yet. I haven't really done anything like this before, so a lot to learn about but it seems like it will be interesting.