97s I/O Pod

[[kby]]

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.

[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

[teenix]

There is also an interface project here that might help understand the works

https://www.hpmuseum.org/cgi-sys/cgiwrap...i?read=937

cheers

Tony

[[kby]]

Thanks for the link to the schematic. I did see the interface one before, but also saw another of Katie's posts mentioning she found it faster to just figure out which board it was on and start swapping chips, so I was planning on the (in my case, ultra) brute-force method. But I'll see if I can glean any information using the schematic; without that I stood no chance.

I did look inside before and didn't see any obvious corrosion or damage; it was fairly pristine. I did try using De-oxit on the funky board connector, though and its mating fingers, though. No change.-kby

[[kby]]

Hi Tony,

Time to order a full set since Katie’s recommendation is to narrow the board and then replace while testing each chip. I don’t have a replacement working board so,have to forgo the first step, unfortunately. Also I (1) don’t have a chip tester and (2) since the risky part is soldering and desoldering which has to be done whether or not I can determine that a specific chip is bad, I figure I’ll just plan on replacing them all, hope I don’t get any DOA chips or cause any infant mortality, and only resort to buying a tester if brute force fails. I did buy a nice desoldering gun primarily for this project, which helps.

I wanted to make sure I decided your handwriting, though. Are all the chips on the third sheet (page 2) 4014, or are some 4016? No insult intended; I have PhD handwriting, which is worse.

[teenix]

(05-28-2020 09:04 PM)[kby] Wrote:  Hi Tony,

Time to order a full set since Katie’s recommendation is to narrow the board and then replace while testing each chip. I don’t have a replacement working board so,have to forgo the first step, unfortunately. Also I (1) don’t have a chip tester and (2) since the risky part is soldering and desoldering which has to be done whether or not I can determine that a specific chip is bad, I figure I’ll just plan on replacing them all, hope I don’t get any DOA chips or cause any infant mortality, and only resort to buying a tester if brute force fails. I did buy a nice desoldering gun primarily for this project, which helps.

I wanted to make sure I decided your handwriting, though. Are all the chips on the third sheet (page 2) 4014, or are some 4016? No insult intended; I have PhD handwriting, which is worse.

If you haven't done it already, I'd still try looking for a warm or hot chip (or component) after the board has been powered for awhile first. It might indicate where the problem lies.

Most look like 4000 series ICs which are still available. One is a 74C174, but 74HC174 is available.

There is an unmarked chip on Control PCB (5), but you should be able to find it on the board.

Yes, they all look like 4014 except for one 4035.

The new chips are reasonably rugged, but these are static sensitive so care will be required while handling. Solder the power pins first (Usually GND - 7 or 8, and VCC - 14 or 16).

One big problem is that there are a couple of HP chips in the circuit.

Control PCB (2) 1818-0965 (not sure about the 9) but I haven't seen a reference to any 1818-0x65 chips, or the 1818-0496 on Data PCB (4). If one or both of these are fried, then (yikes).

These drawings are from the amazing efforts of Tony Duell.

Good luck.

cheers

Tony

[[kby]]

I’m not sure why I had the two of you confused…Mea culpa.-kby