HP-97S External Printer?


I've never seen one of these before but it looks to have been professionally made.

What's really curious about this is that the 97s has no obvious way of using this as printer since it has only 4 flag bits for output. All the other pins on that 50 pin connector are for input with a couple of handshaking lines. Is this auction just wrong about the printer plugging in to the 97s i/o pod?



If you look down the listing, he shows it hooked to a BCD Interface box and then to the HP-97. Check his other listings. He has a HP-97S with the BCD interface listed as a separate auction. From the photos, on the other listing, it looks like the BCD interface box is hard wired to the 97S. A shame he didn't list the entire package as a single listing. You need to win both auctions to have a complete working printer/interface/97S.




I think that the "BCD interface box" mentioned is the 97s i/o pod.
The 97s came with the i/o pod hard wired to the 97, that's what the
"s" indicated. The 4 flag lines for output and all the input pins are
on the 50-pin connector of the i/o box. Unless there is some addition equipment not shown it appears as though this external printer plugs into the i/o pod of the 97s and that's what seems so strange to me.

I may have to bid on this for a chance to see what it's all about.



That's fun to think about. A couple of possibilities:

- It really isn't for output from the 97S, but rather is supposed to echo data sent *to* the 97S; i.e. it's listening on the 97S input bus and printing the data. Why? Perhaps for record or debug purposes? Or, if the measured parameter was intended to be included with whatever thing was being tested/measured as part of its documentation, the ink-printed paper would have been a lot more durable than the thermal print from the HP.

- You could, of course, use the four lines to shove out characters in two or three bit nibbles (using one line as a data strobe), or asynchronously using all four lines. That could then be buffered by the printer until a special "print" byte was received (or, if using two bit nibbles for data, a "print" line was strobed). But doing that AND using those lines for other signaling (for normal input via the pod) would be a mess. Seems pretty elaborate, but I guess if you needed ink hardcopy...

Separate topic: Thanks again for posting on the AAA battery pack trick for classic HP's. (Rather than glue on contacts I used some adhesive copper foil which seems to be working OK and made for a fast build.)




Thanks for the clarification on the 97s and it's i/o pod. I wasn't that familar with the 97s version. If you win the auction, please let us know of your conclusions on how it could work.



I made a minimum bid and didn't win the auction, I hope that whoever was the winner reads this forum and will tell us about it. But, I agree, we might have more fun by continuing with Bob's speculations.....

I think that there must be some other input to this printer box. If so, the printer might indeed be there just to echo the input while the HP-97 crunches it. Sending data 2, 3 or 4 bits at a time via the flag lines would be painfully slow.

Separate topic: Thanks again for posting on the AAA battery pack trick for classic HP's. (Rather than glue on contacts I used some adhesive copper foil which seems to be working OK and made for a fast build.)

Actually what I did was to melt the added beryllium-copper contacts into the plastic of the battery holder. But your solution seems just as good as long as the foil is pretty thick and can take some abuse.

Edited: 23 Aug 2010, 10:17 a.m.


I've used adhesive copper foil strips that are sold in rolls to wire doll houses. Well, I'm actually on my first and only roll. They're thick enough to be soldered, etc. There's even a different shade on the positive and negative foil, but, of course, since they run next to each other in parallel, I have to cut them apart. Perfect for HP classics, thin connections in Spices, etc.

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