Help with HP-97S needed

[Holger Weihe]

Hello,

yesterday I got an HP-97S. :-) Unfortunately I can't get it to work. When the power is connected, the Low-power-LED goes on. When I additionally insert a battery-pack, the LED goes out again. (The battery isn't good, but my other HP-97 works fine with it).

Switching the calculator on causes a short flash of a zero (or similar) at the last digit. After that nothing else happens.

Is this behaviour known to anyone of you? Where can I start? I took the calculator apart and cleaned the contacts of the switches etc, but that didn't help. Could it be a problem of the connector pins between Mainboard and Keyboard part?

Another thing:
The HP-97S came with a plastic device (seller called it HP-Console) that holds the calc and the Interface box. The main screws of calc and box are longer than normal to fix them with the console. Is this console a standard HP part?

Thanks!

Holger

[Katie]

I've never seen the plastic holder that you've described, I don't think that it was made by HP.

You might want to try a good (newly rebuilt) battery pack in the 97S or better still, an external DC power supply. The 97S draws slightly more power than the plain 97 does because of the interface pod. It's only about 30 ma more, but that might be enough to drop the voltage on the batteries enough to cause the display to shut down.

[Holger Weihe]

Thanks, Katie and David!

I'll try an external DC supply first before rebuilding the battery. (I hope I won't toast it... :-))

If it doesn't work, I think there was a service manual on the museum dvd, but probably it will be to high for my rudimental electronics skills...

Holger

[David Smith]

Generally, you need a good battery in an HP97 for it to operate properly. Some machines can get by without one (if no printer or card reader is used), but many will be totally dead without one.

[Holger Weihe]

Hello,

By now I have tried to run the HP97 with the AC-cable connected and an additional 5 volts DC supply at the battery connectors. Nothing happend. I increased the voltage until at about 8 volts the display went on (showing a mutaded zero at the right side). The printer moved. But the calc doesn't respond to any keypresses. By the sound of the printer I got the impression that it is stuck somehow. Could this prevent the HP-97S from properly starting?

When running it without DC supply, the printer makes some humming sounds when I press the paper-feed button. But it doesn't seem to move.

Any advice what I should try know?

Thanks!

Holger

[David Smith]

Yes, a bad printer can cause the machine to lock up. When powered on, the machine wants to see the head in the HOME position. Some firmware versions even cycle the print head whenver the machine is powered up. If the printer is jammed it will stay dark or say ERROR.

[Katie]

Holger,

Don't crank up the voltage on the external DC supply, 5.0 - 6.0 should be fine. Is the supply able to provide enough current? The printer and card reader need quite a lot maybe 500 ma to 1 A peak. Even with neither of those running but just the display, it will use up to 250 - 300 ma. If your supply can't provide enough current, it may very well sound like your printer is stuck. Did you try turning the printer gears by hand to see if it is in fact stuck?

-Katie

[Holger Weihe]

Thanks, again!

My DC supply can deliver 2.5A, that should not be the problem. Nevertheless I bought some new cells today and will build up a good battery pack. Then I will have a closer look to the printer. Checking the resistors and diodes there should also be possible for me. I don't have an osciloscope, but my DMM can measure frequencies. Maybe that'll help to follow some signals after I studied the service manual. (If I understand enough of it...)

I'll come back to the forum when I succeed, or when I am able to ask more detailed questions... :-)

Holger