HP-71B Chirp (solved)

[Sylvain Cote]

I received a HP-71B today (s/n: 2401A00190) and it has the same behavior as Adam Jones’s unit in 2013.

The small computer emit a chirp (brief sound) each time the display is changed, a key is pressed on in some cases at each minute.

Test cases:

1. on blinking cursor : a chirp is emitted at each .5 seconds
   
   Code:
   

   cursor on, cursor off, cursor on, cursor off, ...
   .
2. on key press .......: a chirp is emitted on each key press detected by the internal keyboard scanner
   
   Code:
   

   there is a lot of chirp going on if I press the left arrow and keep pressing the key
   .
3. at each minute ....: a chirp is emitted at each minute when the display is frozen
   
   Code:
   

   DISP "TEST3" [ENDLINE] then wait for the chirp, no key pressed
   .
4. on display update : a chirp is emitted at each 3 seconds until the for/next is completed, then at each minute if I do not press any key.
   
   Code:
   

   DELAY 3 [ENDLINE]
FOR I=0 to 10 @ DISP "TEST4" @ NEXT I [ENDLINE]

Some clue as to what could be the cause of this ?

Thanks,

Sylvain