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HP 21 not powering on - repair/troubleshooting advice
01-28-2021, 12:17 AM (This post was last modified: 01-28-2021 12:52 AM by dmh.)
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RE: HP 21 not powering on - repair/troubleshooting advice
(01-27-2021 06:02 AM)Steve Simpkin Wrote:  
(01-27-2021 04:42 AM)dmh Wrote:  Ok, a bit surprised as visually the terminals looked ok but some light abrasion to the terminals has given the following:

- one powers on and works fine except for the '4' button. It clicks like all the other buttons. Any suggestions?

- one shows some screen activity as the power switch is turned off or on but never stays on. Shows either one '0' on left or right or three '0' across the screen. Is this the ACT chip or could it just be the power switch?

- last one still does nothing


For the one with a non functional key, there is a small hole on the keyboard circuit board under each key. Take a stranded small gauge wire and spread the individual wires to make a fine wire brush. Using this and a small amount of contact cleaner, insert one of the wire strands into the hole behind the malfunctioning key and work it around to clean the key contact.

I don't have any contact cleaner but tried this with just the wire strands and now the '4' key basically works - thanks :-).

It doesn't register every time so can I use anything else around the house like vinegar?

The '5' key also double presses so will try the same thing with that.

Looks like I will have at least one working 21 so very happy about that :-)

Thanks everyone!

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RE: HP 21 not powering on - repair/troubleshooting advice - dmh - 01-28-2021 12:17 AM

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