Some issues with my HP-97

[Moggul]

I just acquired an HP-97 in pretty good condition. This is my first LED calculator (so far my collection was made up of Pioneers, Voyagers and other LCD calculators) so I am a bit out of my comfort zone.

After charching the battery the calculator works just fine. However there are some issues that need addressing:

- Program cards are not loading as they just advance a bit before the message "error" appears. I will try to rebuild the card reader using the instructions found on this forum and will post my progress

- The calculator goes blank after I press any key related to printing (print X, advance paper, print stack, ...). I suspect the printer is not working correctly so maybe I will just disconnect it. any tips for doig this?

- The calculator makes a loud buzzing sound. I believe it is either the printer or the card reader, probably the former. Looks like the printer motor is always engaged. Any ideas?

Here is a pic of the calculator happily sitting on my desk

[teenix]

(10-17-2019 07:08 PM)Moggul Wrote:  I just acquired an HP-97 in pretty good condition. This is my first LED calculator (so far my collection was made up of Pioneers, Voyagers and other LCD calculators) so I am a bit out of my comfort zone.

After charching the battery the calculator works just fine. However there are some issues that need addressing:

- Program cards are not loading as they just advance a bit before the message "error" appears. I will try to rebuild the card reader using the instructions found on this forum and will post my progress

- The calculator goes blank after I press any key related to printing (print X, advance paper, print stack, ...). I suspect the printer is not working correctly so maybe I will just disconnect it. any tips for doig this?

- The calculator makes a loud buzzing sound. I believe it is either the printer or the card reader, probably the former. Looks like the printer motor is always engaged. Any ideas?

Here is a pic of the calculator happily sitting on my desk

If the card reader is original, then it will likely need attention. Be careful removing the ribbon cable as the ends can be damaged if it is held firm in its connector. Only one end needs to be unplugged. The plastic balls and idler can drop out when the card mechanism is opened and then miraculously disappear. You will need some needle nose pliers to remove the main board wiring connectors without pulling on the actual wire. Take photos of the disassembly to help put it back together..

Be careful prying the circuit boards apart. The connectors are flexible but brittle and can break. The boards can be lifted out bit by bit using some gentle leverage with (say) a screw driver alternating along length of the connector. I wouldn't try to pull them apart. Local finger pressure along the edge of the board will assist in replacement.

I have spare O-rings and I can make up a drive coupler and post if you need them.

The display normally turns off when printing so as to maximize battery power to the printer, but it sounds like it has a problem. Check for corrosion on circuit boards and connection contacts.

The printer board can be unplugged from the main board, but will need to be isolated so it doesn't short anything it you want to try it out quickly.

You can check the printer board (both sides) without removing the print head ribbon cable. If you do need to remove this cable, it is a destructive process unless you have a "tool" and follow the correct procedure. There is plenty of discussion on the forum.

Google HP-97 service manual, it has good info in it.

Happy to help further if you need it.

cheers

Tony

[Paul Berger (Canada)]

If the printer motor keeps running I would suspect that it has the original plastic idler gear that has gone rotten and the teeth stripped off it, there are aluminum replacements available.

Paul.

[Archilog]

Hello, Moggul,
Teenix and Paul Berger told you what you need to know.
I post my comment to tell you how superb this (your) calculator is.
Thanks for your picture. Take care...

[Moggul]

I just opened the calculator and found half plastic idler gear loose inside. As a result of this the motor spins freely when the calculator is powered on. Please see attached pic and video below.

https://www.youtube.com/watch?v=qsv8N7GFpEg

I have ordered the metal brass gear form Germany (3 pieces just in case I mess up with the drilling) and will be posting updates soon.

Also the O-rings for rebuilding the card reader have already been ordered.

The adventure continues!!!

[Paul Berger (Canada)]

As mentioned by Tony above, the flat cable for the card reader is difficult to remove, I slip a thin piece of plastic, cut from a flat PET plastic package, between the pins on the connector and the cable and then the cable is easily removed. If you try to pull it out without inserting something like this between the cable and pins you stand a very good chance of damaging the cable and/or the connector. The other problem with these cables is they are made up of strips of flat metal laminated between layers of plastic and over time they may delaminate, if it is only beginning to come apart I have had some success stabilizing cable of this type with cyanoacrylate glue.

Paul.