97s I/O Pod

[teenix]

(06-06-2019 03:18 AM)[kby] Wrote:  So I have a 97s with a non-functioning I/O pod. The calculator itself looks fairly good, although one post broke when removing the back, and the cable does look like someone accidentally dropped a soldering iron on the plug to the umbilical cord. However, it looks at the moment like the damage is mostly cosmetic—a little insulation melted/burned off on one or two of the wires, but the wires themselves look fine. I will check these with a meter to make sure the cable seems OK, but, assuming that passes, I'm debating where to go next. The symptom, incidentally, is that the I/O pod diagnostic doesn't run at all (never gets an interrupt from the pod). The calculator passes the calculator diagnostic fine.

I read Katie's post that the easiest way would probably be to swap boards with a good pod to narrow the bad board and then replace chips on the one discovered bad. Of course, I don't have a good pod to try that with, so I'm figuring I had just better count on replacing all the chips one by one, so, to that effect:

Is there a convenient list of all the chips used in the I/O pod (preferably with their modern equivalents)?

Is there a "best place" to guess the problem might be so that I can start with replacing the most commonly failing elements first?

I don't have a scope or a logic probe; I do have a decent DMM (Fluke 189), so I will also probably check to make sure that the right signal gets generated out of the calculator to the pod, but, beyond something showing up there, is there any input on the above two questions? Thanks in advance.

This is a circuit for the module.

http://www.hpcc.org/cdroms/schematics5.0...p97sio.pdf

Most chips look like common CMOS 4000 series chips.

If any of these are bad then they might warm up after being on for awhile. It's a complex circuit so I'd start by checking for usual circuit board corrosion etc, then the power supply voltages around the circuit.

cheers

Tony