hp 20s self test


I can't get the self tests to work even though the calc works ok with the basic stuff. My manuals and DVD are at the office for safe keeping and are not accessible.


Charlie in phx




Edited: 23 Dec 2007, 12:26 p.m.


Thanks Gerson.

I had found this site and more but my problem is in running the tests. When I do the 2 key thing it is as if I merely turned on the calc. I have done these tests many times with many models and the tests would always run.

The keys feel good and do their functions except for the tests.

Maybe I'm just missing the necessary brain cells.


With 0.0000 on the screen do you get an error when you press 1/x or nothing? If nothing, the 1/x key is missing contact, if you get an error, your ON button may be intermittent.

Try pressing E then ON+E This should start the loop test. You can also set up a similar scheme with the y^x key to see which (if any) are not contacting.

The pioneer series is fascinating combination. One that RSKEY missed in their excellent website is that the Pioneers all have slightly different ON-D tests. Included below for reference.


Maybe I'm just missing the necessary brain cells.

No, the procedure as written is just lacking. The various models of Pioneers need slightly different methods then just pressing two keys.

For the 20S LCD/Keyboard test:

  1. Turn it on
  2. Press and hold down the ON key
  3. Press and release the y^x key
  4. Release the ON key
You can now press any key, repeat three times to cycle through all display segments. After the fourth press, you will you see the HP copyright displayed for a few seconds and the display will then be 00 with a shift annunciator and PEND displayed. Then press each key in order, top left to bottom right. The display will increment with each good key.

The reset procedure is similar:

  1. Press and hold down the ON key
  2. Press and release both Sqrt and E+ keys simultaneously
  3. Release the ON key
  4. See ALL CLr


I haven't been able to find any HP-20S manual other than this one in Portuguese, which may be useless to you. Anyway, I hope this excerpt from the original manual helps:

1. First, hold down the [C] key, then press and hold [y^x]. (A continu-
ous selft-test can be performed by holding down [C] as you press
[1/x]. This test displays various patterns and the copyright message,
then automatically repeats. The test continues until you halt it by
pressing [C].)
2. Press any key four times, and watch the display as various pat-
terns are displayed. After pressing the key four times, the
calculator displays the copyright message COPr.HP 1987 momen-
tarily, and then the message 01. This indicates the calculator is
ready for the key test.


Edited: 23 Dec 2007, 4:29 p.m.


Thank you Gerson, Allen (I'll save your chart) and Randy! It passed both tests.

Merry Christmas!

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