HP48SX - shift keys won't stay shifted

[Bruce Larrabee]

I've got a HP48SX. It's shift keys ( left, right, alpha) won't stay shifted. When you push the key the annunciator comes up but when you release the key it goes away again. Has anyone encountered this? Any solutions?

[Han]

(03-07-2014 09:05 PM)Bruce Larrabee Wrote:  I've got a HP48SX. It's shift keys ( left, right, alpha) won't stay shifted. When you push the key the annunciator comes up but when you release the key it goes away again. Has anyone encountered this? Any solutions?

Is this an annunciator/screen issue? In other words, (ignoring the actual annunciator) if you press [Alpha] followed by [A] does the command line still produce the letter A? Or does the calculator think you only pressed the soft menu corresponding to A?

[Bruce Larrabee]

No it's not a screen issue. When I press down on the key the annunciator appears on the screen, when I release the key it goes away. More specifically none of the shifted functions are available. Only the white functions on top of the keys are available.

[Mark Hardman]

(03-07-2014 09:05 PM)Bruce Larrabee Wrote:  Any solutions?

Have you tried doing a reset with On-A-F?

Mark Hardman

[Bruce Larrabee]

I did a reset with the hole in the back but the machine won't do a on-a-f reset.

[W_Max]

It's most likely hardware problem.

Look at this board. You can see dirty keyboard contacts. To locate problem you can heat calc a little (by hair dryer, flowing to shoebox, where calc is placed or directly to calc back). The problem may be temporary eliminated, but I'm afraid, that you must disassemble this machine for keyboard prophylactic works.

[Han]

The keys clearly work because the annunciators turn on when the keys are pressed. If holding down the shift key and pressing a second key works, then my guess is that something is triggering a secondary key press to nullify the intended single key press (among the shift keys).

[W_Max]

The same symptom can indicate weak contact group (or electrical short between contacts, caused by conductive parts from keyboard ribbon - you can see those black areas on keyboard contact group at the photo above) You can try to press overlay under the LCD (between LCD and function keys) and try to press shift keys again.