HP-91 OOPs

[teenix]

Hi all,

Does anyone know if the HP-91 had an Out Of Paper switch?

Tony Duell's circuit suggests there was one, but there was no wiring for it in a 91 from the printer to the printer sub board. The printer mechanism also does not have the out of paper sense plate.

The connectors for the wiring have not been installed on the circuit board either and the soldering look like a factory finish.

cheers

Tony

[tangdfx]

Hello，Tony

I just check my HP91.

I can not find a OOP switch.

[teenix]

Thanks for that :-)

I think the 91 came out before the 97 which does have the switch, so maybe the paper out was an added feature.

It's interesting that the 91 circuit boards support the switch though.

cheers

Tony

[rprosperi]

The 91 definitely came out earlier, but not by much, March vs. July of '76.

But IMHO, that was long enough for them to figure out that an OOP sensor was needed, as all it took was running out once to realize it's a necessity for a desktop machine that prints a lot.

[brouhaha]

(07-13-2024 12:15 PM)rprosperi Wrote:  The 91 definitely came out earlier, but not by much, March vs. July of '76.

But IMHO, that was long enough for them to figure out that an OOP sensor was needed, as all it took was running out once to realize it's a necessity for a desktop machine that prints a lot.

Also the OOPS sensing is much more important for the programmable 97, since it might be running unattended. Rather than continuing and failing to print, it will stop so that you can load more paper when you notice, then resume running.

[rprosperi]

Thanks Eric, this is clearly the key reason to add this, and though it should have been obvious, I didn't think of it. I also didn't realize the paper-out condition would pause program execution until paper is restored. That's HP engineering at its best.

[Roland57]

The OOP switch is not a hp97 specific feature: my financial calculator hp92 has the OOP switch installed too.

Roland

[teenix]

(07-14-2024 06:57 AM)Roland57 Wrote:  The OOP switch is not a hp97 specific feature: my financial calculator hp92 has the OOP switch installed too.

Roland

Makes sense if the 92 came after the 97.

I guess with the 91, the engineers had it in mind and prepared to implement it but didn't. After the 97 I suppose it became a good idea and the 92 then got it. The 91 has similar OOP circuitry to the 92, just not used.

[Jake Schwartz]

[/quote]

Makes sense if the 92 came after the 97.

I guess with the 91, the engineers had it in mind and prepared to implement it but didn't. After the 97 I suppose it became a good idea and the 92 then got it. The 91 has similar OOP circuitry to the 92, just not used.
[/quote]

Agreed - the HP-92 (7/1/1977) was introduced a full year after the HP-97 (7/1/1976).
Jake

[teenix]

It would seem that the 91 and the 97 were on the engineers minds quite early on. The 91 internal plastic assemblies have the mounting hardware for the card reader and slots for the ribbon cable.

[rprosperi]

(07-17-2024 11:56 PM)teenix Wrote:  It would seem that the 91 and the 97 were on the engineers minds quite early on. The 91 internal plastic assemblies have the mounting hardware for the card reader and slots for the ribbon cable.

Interesting! Thanks for sharing this Tony, it fills in some little discussed history. Long, long ago, probably at an HHC meeting in the early 80's, I was told by (someone) from HP that the 91 introduction was delayed over internal discussions, planning, etc. about these features and which model would have what, but at the time, it didn't register as a notable comment to dig into as at that time, these were merely 'old models' and not of interest to me from a historical perspective.

What is the mfg date of the sample you see this in?

The 91 was introduced in March '76 and the 97 in July of '76, so it's possible they changed over to the newer style case with the mounting h/w, etc. once the 97 design was completed to only source one master part? Just speculating... but interesting to me now.

[teenix]

(07-18-2024 01:35 AM)rprosperi Wrote:  What is the mfg date of the sample you see this in?

1607A03021

Looks like Feb'76

[rprosperi]

(07-18-2024 05:56 AM)teenix Wrote:  

(07-18-2024 01:35 AM)rprosperi Wrote:  What is the mfg date of the sample you see this in?

1607A03021

Looks like Feb'76

Thanks, and this exactly supports the idea that accepting the card reader in the 91 was in from the beginning, as the case molding was likely one of the longest lead items in production planning,

But another interpretation is they were actually planning to issue the 97 with CR support from the beginning, but as development of that was slow due to the new technologies (CR, programming) they chose to issue the 91 as an interim model to capture some desktop scientific users while finishing the 97.

Either way, I imagine a lot of the earliest 91 buyers were a bit disappointed (ok, pissed off) when the 97 appeared only a few months later. (corrected earlier to later)

Thanks Tony!

[Massimo Gnerucci]

(07-18-2024 12:00 PM)rprosperi Wrote:  

(07-18-2024 05:56 AM)teenix Wrote:  1607A03021

Looks like Feb'76

Thanks, and this exactly supports the idea that accepting the card reader in the 91 was in from the beginning, as the case molding was likely one of the longest lead items in production planning,

But another interpretation is they were actually planning to issue the 97 with CR support from the beginning, but as development of that was slow due to the new technologies (CR, programming) they chose to issue the 91 as an interim model to capture some desktop scientific users while finishing the 97.

Either way, I imagine a lot of the earliest 91 buyers were a bit disappointed (ok, pissed off) when the 97 appeared only a few months earlier.

Thanks Tony!

Unfortunately I exchanged my 1604A00023 for a 92 in order to complete my collection, or I could check an even earlier item.

[teenix]

The 91 and 92 are basically an identical setup except for the switches. Internally though, they connect the same to the ACT.

Also, the 92 has a different key matrix. I don't know why they would bother designing a circuit board different than the 91 given that they have the same key layout, but maybe the microcode needed different key codes to function properly or was easier to code for.

In all Topcats, the paper advance switch is detected by the ACT, but the 91 appears to have a special instruction to tell the PIK chip to print a short blank line when the paper advance key is pressed, whereas the 92 and 97 execute normal printing PIK codes.

cheers

Tony